Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Pulsed light processing of foods for microbial safety

Pulsed light processing of foods for microbial safety The demand for processed foods and the awareness about food quality and safety are increasing rapidly. The consumers’ demand for minimally processed foods and growing competition in the market have made the processors to adopt newer non-thermal technologies that preserve nutrients and sensory properties of the products. Conventionally, heat processing of foods is carried out to convert raw material into value-added product, reduce or eliminate microbial load to improve safety, and extend shelf life. Some of the limitations of thermal processing techniques can be overcome by employing non-thermal processes. High hydrostatic pressure, pulsed electric field, ultrasound, cold plasma, dense phase carbon dioxide, ozone, and pulsed light (PL) processing are gaining popularity in food processing. PL technology is a non-thermal technology, where sterilization and decontamination are achieved by impinging high-intensity light pulses of short durations on surfaces of foods and high-transmission liquids. Although a few reports on the PL technology are available, in-depth studies on this are needed to adopt at a commercial level. The present review provides an overview of light-based processing of foods and covers important aspects such as different PL systems used for processing of foods, mode of action of PL on microbes, the effect of PL on liquid foods, surface decontamination of foods and parameters that affect PL efficacy, combination processing with PL. With the growing demand in non-thermal processing for the technological advancement in the area of generation of light, light-based processing will be a promising technology for microbial load reduction. Key words: Pulsed light; Food safety; Non-thermal processing; Minimally processed; Microbial load. of colours and vitamins (Devlieghere et al., 2004). High-temperature Introduction short-time processes, electromagnetic radiation-based microwave, As the human evolution progressed, the way food being consumed radio frequency heating, and ohmic heating techniques have gained and their priorities have also been evolved. The consumption of focus in the recent past as alternative and rapid heating techniques to processed foods is on the rise due to change in lifestyle, particularly minimize the severity of heat treatment and thereby enhance product in urban areas. Traditional thermal-based food-processing methods quality. such as appertization, pasteurization, and canning have been Over the past few years, consumer demand for fresh, natural, dependent on high temperature, to ensure prolonged shelf life and minimally processed foods with better quality has increased. and food safety. Although thermal processes are efficient tools To address this, researchers are working on developing alternative for microbial inactivation, they also contribute to undesirable techniques that not only meet the consumer demand but also energy- changes in food matrix such as structural alteration of proteins efficient, cost-effective, and rapid. Many novel technologies that and polysaccharides, production of free radicals, affecting the functionality of food and flavour, textural softening, and destruction do not involve heat processing have been developed to inactivate © The Author 2017. Published by Oxford University Press on behalf of Zhejiang University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 188 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 microorganisms. The novel non-thermal technologies such as high per the literature reports available, the three major commercial hydrostatic pressure (HHP), pulsed electric field (PEF), ultrasound companies producing disinfection systems based on PL are (US), cold plasma, dense phase carbon dioxide, ozone, and pulsed SteriBeam Systems from Germany, Xenon Corporation from USA, light (PL) processing are gaining popularity in food processing. and Claranor from France. Experiments conducted by Hierro et al. These technologies hold several promises by preserving the delicate (2011), Lasagabaster et al. (2011), Ramos-Villarroel et al. (2014), sensory and nutritional qualities of food and hence used for minimal Maftei et al. (2014), Koh et al. (2016a), Moreira et al. (2017), processing of food products (Ortega-Rivas and Salmerón-Ochoa, and Valdivia-Nájar et al. (2017) are associated with SteriBeam, 2014). These technologies offer several advantages compared to whereas results reported by Keklik et al. (2010), Wambura and thermal processing by minimizing the effect of heat on food and Verghese (2011), Pataro et al. (2011), Muñoz et al. (2011), Gómez minimization of flavour loss (Norton and Sun, 2008; Soliva-Fortuny et al. (2012a,b), Xu et al. (2013), and Huang and Chen (2014) et  al., 2009; Chawla et  al., 2011; Misra et  al., 2011; Rastogi, were obtained with a Xenon Corporation device, mainly the model 2011; Thirumdas et al., 2015; Wang et al., 2016). Among the non- SteriPulse™-XL 3000. Artíguez et al. (2011), Levy et al. (2012), thermal technologies, one of the emerging technologies is light- Nicorescu et al. (2013), Manzocco et al. (2014), Ignat et al. (2014), based processing. The present review deals with the usage of this Fernández et al. (2016), and Rajkovic et al. (2017) carried out the technology for microbial load reduction in foods. experiment with the PL system from Claranor with multiple xenon lamps. MacGregor et al. (1998) used a PL generator including rectangular PVC housing, pulse generator, and a control circuit PL Processing for bacterial inactivation. This bench-top experimental facility had two inoculated Petri dishes inclined at 45° received equivalent PL technology is a non-thermal technology, where decontamina- doses. Takeshita et al. (2003) studied the damage caused by PL tion of foods such as fruit juices, meat products, vegetables, and on Saccharomyces cerevisiae using the system similar to that fruits is achieved by using high-intensity light pulses for a short designed by Dunn et al. (1995) having power supply unit and a duration of time. The PL includes a wide wavelength range of 200– flash lamp that produce PL consisting of intense flashes of broad- 1100 nm, which includes ultraviolet (UV): 200–400 nm, visible spectrum white light (200–1000 nm). Fine and Gervais (2004) used (VIS): 400–700 nm, and near-infrared region (IR): 700–1100 nm One-Shot EN2/2143-1 unit, a 3-fluidized bed as a PUV system (Elmnasser et al., 2007; Palgan et al., 2011). The term pulsed light is having adjustable air nozzles and compressed air that allows known since 1980 and was first adopted by the US Food and Drug tangential blowing for fluidization of the food powders; flash lamp Administration (FDA) for food processing in 1996 (FDA, 1996). surrounded by a quartz jacket with water circulation to limit lamp To increase the safety of fruit and vegetable juices, US FDA regula- overheating and a reflecting cylinder. Paskeviciute et al. (2011) and tion has implemented 5-log pathogen reduction process (US FDA, Luksiene et al. (2012) constructed high-power PL device in their 2004). Significant microbial reduction in very short treatment time, laboratory having a chamber, a reflector with a flash lamp, and a low environmental impact, and its high flexibility are some of the power supply for chicken, vegetable, and fruits decontamination, major benefits of PL (Uesugi and Moraru, 2009; Oms-Oliu et  al., respectively. Sharma and Demirci (2003) and Ozer and Demirci 2010b). Xenon flash lamps are more environment-friendly than (2006) conducted the experiment to decontaminate the alfalfa continuous-wave UV lamps as they do not use mercury (Gomez- seeds and fish fillets, respectively, using a PL sterilization chamber Lopez et al., 2007). One of the big advantages of PL over static UV containing treatment chamber, UV strobe, tray, and a control treatment is the fact that the energy is delivered in a very short time module. Similarly, Bialka and Demirci (2007) used a laboratory (Sauer and Moraru, 2009; Chaine et al., 2012). PL systems have scale, batch PL system for decontamination of blueberries with relatively low operation costs and generate only reduced amounts slight modification in the set-up having a quartz window and a of solids wastes (Pereira and Vicente, 2010). The benefits include cooling blower. PUV treatment was carried out in the continuous reduced risk from foodborne pathogens on public health, extended flow-through system for inactivating Staphylococcus aureus in the shelf life of the product, and improved economics during food milk. The system included a UV chamber, UV lamp, pump with distribution (Ozer and Demirci, 2006). PL has potential applica- variable flow rate, and V-groove reflector (Krishnamurthy et al., tions in food processing that requires a rapid disinfection where 2007). surface contamination is a concern for microbial contamination Choi et  al. (2010) designed a laboratory-scale PL system for such as fresh whole fruit and vegetable commodities, hard cheeses non-thermal sterilization of infant foods. They used water bath as or meat slices, and so on. Even though the PL processing is consid- a cooling device to dissipate the heat generated during the discharge ered as ‘non-thermal’, it has the limitation of sample heating due by quartz lamp and oscilloscope to view the exponential decay pulse. to longer treatment time, which may cause thermal inactivation of Cheigh et al. (2013) designed a laboratory-scale PL system consisting microbes. Significant temperature increase caused due to longer PL a xenon lamp used to produce intense pulsed light (IPL) with an treatments has an extra effect on microbial reductions depending emission spectrum in the range of 200–1100  nm for inactivating on the matrix properties (Bialka and Demirci, 2008; Huang and Listeria  monocytogenes on solid medium and seafoods (Figure  1). Chen, 2014). Hwang et  al. (2015) designed an ILP treatment unit for microbial inactivation of various liquid samples, which had a pulse generator PL Treatment Systems for Microbial Load and a spectroradiometer to determine the irradiance of xenon Reduction lamp, cooling system (fans) on either sides of the lamp to dissipate The pioneer company producing PL equipment for application the generated heat. Similarly, Yi et  al. (2017) also self-designed a in water purification systems and virus inactivation systems for laboratory-scale IPL for describing the IPL inactivation curves of biopharmaceutical manufacturers is Purepulse Technologies Inc. Pseudomonas  aeruginosa under different pulse conditions. Hwang (San Diego, California), a subsidiary of Xenon Corp., which et  al. (2017) constructed a pilot-scale IPL device by upgrading commercialized the PureBright™ system (Dunn et al., 1995). As the xenon lamp and power supply. Sesame seeds inoculated with Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 189 bacteria, moulds, and yeast were treated using this PL system. Pataro power also contribute to the destructive effect on microorganisms et  al. (2011) carried out microbial-inactivation experiments using (Elmnasser et al., 2007). The antimicrobial properties of UV light a laboratory-scale continuous-flow PL apparatus which consisted on bacteria are attributed to absorption of radiation by conjugated of a linear Xenon flash lamp, power/control module, sterilization carbon–carbon double bonds in nucleic acids and proteins, and chamber, photoelectric detector module, and cooling system subsequent DNA structural changes (Ramos-Villarroel et al., 2012). (Figure 2). Ferrario and Guerrero (2016) performed PL treatment in Cheigh et al. (2013) identified the cell damage on the foodborne apple juice with the help of a continuous flow-through PL system. pathogen, L. monocytogenes treated with UV-C and IPL with the Caminiti et al. (2011b), Muñoz et al. (2012), and Chaine et al. (2012) help of transmission electron microscopy (TEM). UV-C–treated L. also used a continuous flow-through PL system for processing liquids monocytogenes cells were similar in structure to that of untreated like fruit juices and sugar syrup. cells except for a blurry and indistinct cell wall (Figure 3). In contrast, IPL-treated cells showed the destruction of cell wall structures, cytoplasm shrinkage, and rupture of the internal organization leading Mode of Action of PL on Microbes to leakage of cytoplasmic content and ultimately to cell death (Cheigh UV was the only agent responsible for the inactivation of pathogens et al., 2012). But, conversely, Krishnamurthy et al. (2010) concluded and no antibacterial effect attributed to IR or VIS light was found that S. aureus treated with PUV had cell wall damage, disintegration, (Paškevičiūtė and Lukšienė, 2009; Ramos-Villarroel et al., 2014; cellular content leakage, cytoplasmic membrane shrinkage, and also Kramer et al., 2015). In addition, it has been shown that both found that internal cellular structures were collapsing. Cheigh et al. the VIS and IR regions of PL in combination with its high peak (2012) also indicated that the IPL treatment was effective in reducing the bacterial population in L. monocytogenes and Escherichia coli O157:H7 than continuous UV-C irradiation. However, despite a high energy density and broad spectrum (with wavelengths including the UV-C region), IPL treatment exerted milder photochemical effects on the cells (e.g. the formation of double-strand breaks) than did UV-C irradiation. Levy et al. (2012) mentioned that PL had a better effect than continuous UV treatment for Aspergillus niger spores. Similarly, Orlowska et al. (2013) also found 5-log reduction of E. coli in water at 10 mJ/cm for continuous mercury lamps and at 5 mJ/cm for pulsed lamps. Nicorescu et al. (2013) studied the effect of PL on the structural differences in Bacillus subtilis inoculated on powdered spices with the help of scanning electron microscopy (SEM). The cell membrane was disrupted clearly forming deep craters in the cell wall after PL treatment, whereas it was contrary in the case of B. subtilis treated in suspension (Figure 4). The cell wall disruption may be due to photothermal stress and germicidal action caused by the PL having a UV component. It altered the DNA structure by decreasing supercoiling of DNA and then breaking into a single strand that in turn leads to cell death (Nicorescu et al., 2013). Xu and Wu (2016) studied the structural difference in E. coli treated with PL and confirmed that the structural changes in membrane integrity of E. coli, leading to flattening of cells, can be due Figure 1. Schematic diagram of the intense pulsed light (IPL) system (Cheigh to heating of intracellular fluid, and UV light absorption by bacteria et al. 2013). Figure 2. Schematic diagram of the continuous flow PL system (Pataro et al., 2011). 190 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 health status. Inactivation of these pathogens on liquid food complexes are mentioned in Table 1. PL processing is influenced by various factors that dictate its efficiency on microbial inactivation, retention of quality, and other properties of the product. Important factors that determine the effectiveness of PL is the fluence level applied on the sample, the amount of energy (dose or number of pulses) and wavelength of light/composition of the spectrum (Ramos-Villarroel et al., 2012). Inactivation of microbes is higher for PL treatment with higher pulse number and higher intensity (MacGregor et al., 1998; Maftei et al., 2014; Ramos-Villarroel et al., 2014). It is indicated that when the spectral range of the PL treatments, particularly the UV component, is altered by using filters, the inactivation of E. coli and Listeria innocua is lower (Ramos-Villarroel et al., 2012). And among the sub-divisions of UV, UV-C–containing spectrum was more effective in inactivating B. subtilis and A. niger spores (Levy et al., 2012). Absorption of light, particularly in the UV region, and shielding of microbes by suspended matter are significant limiting factors in PL treatment of microbes in liquid substrates (Sauer and Moraru, 2009). PL has very limited penetration depth in opaque media and is capable of targeting the surface microorganisms. Penicillium expansum inactivation efficiency of PL treatment dramatically decreased from 3.21 to 1.58 log colony forming units (CFU)/ml when the depth of apple juice was increased from 6 to 10 mm (Maftei et al., 2014). Inactivating effect of PL treatments against P. expansum was greatly depended on the microbial load that is 1.30 and 3.2 log reduction 5 4 for 3 × 10 and 2.3 × 10 CFU/ml, respectively, for inoculated juice samples (Maftei et al., 2014). The susceptibility trend is reported to be Gram-negative bacteria > Gram-positive bacteria > bacterial spores > fungal spores (Rowan et al., 1999; Anderson et al., 2000; Levy et al., 2012). S. cerevisiae was found to be the most resistant strain to PL treatment than L. innocua, E. coli, and Salmonella enteritidis in PL-treated apple juice system (Ferrario et al., 2015b). In contrast, Nicorescu et al. (2013) have reported that bacteria is more resistant than yeast for PL treatment, whereas viruses are more resistant to PL treatment compared to bacteria (Huang et al., 2017). Gram-negative bacteria, E. coli, is more susceptible to PL when compared to Gram- positive bacteria, L. innocua, which may be due to the presence of distinguishing structural/compositional variation in the cell walls of these bacteria (MacGregor et al., 1998; Otaki et al., 2003; Ramos- Villarroel et al., 2011; Ramos-Villarroel et al., 2012). E. coli is more sensitive to UV-C treatment than L. monocytogenes as the Weibull model parameters also confirms, which is a better fit compared to Figure  3. TEM of L.  monocytogenes: (A) untreated, (B) treated with 150 the linear model for evaluation the microbial inactivation (Bialka pulses (30 s), (C) treated with 900 pulses (180 s) with IPL at a fluence of 1.75 and Demirci, 2008; Bialka et al., 2008; Chun et al., 2010). Bacillus mJ/cm per pulse, and (D) treated for 1000  s with UV-C at 254  nm (Cheigh is more susceptible than mesophilic bacteria, and L. innocua is more et al., 2013). resistant than Pseudomonas fluorescens to PL at low temperature and low fluence levels (Luksiene et al., 2012; Hilton et al., 2017). Hilton can be attributed to overheating, intercellular water vapourization, et al. (2017) indicated that PL treatment effectiveness is independent and subsequent membrane disruption. PL processing is a multi- of temperature for E. coli and P. fluorescens in clear liquid substrates target process in which both photothermal/photophysical and within the temperature range of 5–40°C. However, in the case photochemical effects are caused, thus alteration in cell membrane of L. innocua, the effect of temperature and PL was observed at disruption/leakage of cell content and chromosomal DNA damage 50°C. Higher PL resistance shown by Listeria spp. compared to occurs, respectively (Cheigh et al., 2012; Ramos-Villarroel et al., Pseudomonas phosphoreum and Serratia liqueficans could be 2012; Nicorescu et al., 2013). related to the presence of photoreactive substances and protective compounds that contribute to the antimicrobial effectiveness of PL (Lasagabaster and De Maranon, 2012). Ramos-Villarroel et al. Effect of PL on Liquid Foods (2011) mentioned that IPL sensitivity by microorganisms may be PL processing is being applied on various liquid products for related to differences in bacterial cell wall composition due to their decontaminating the foodborne pathogens that affect the human protective and repair mechanisms against the damage. PL induced Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 191 Figure  4. (i) SEM of B.  subtilis vegetative cells in suspension: (a) untreated samples; (b) treated by PL at 0.6 J/cm /flash. (ii) SEM of ground black pepper artificially inoculated with B. subtilis vegetative cells: (a) untreated samples; (b) treated by PL at 1 J/cm /flash (Nicorescu et al., 2013). Table 1. The effect of PL treatment on microbial inactivation in liquid foods. Food product Microorganism Treatment Log reduction Reference Milk S. aureus 3 pulses/s and 1.27 J/cm /pulse; distance from the UV 0.55–7.23 log CFU/ Krishnamurthy et al. light strobe 5–11 cm; flow rate 20–40 ml/min ml (2007) Apple juice E. coli ATCC 25922 Frequency 3 pulses/s and pulse width 360 µs: 2.66 log CFU/ml Sauer and Moraru E. coli O157: H7 fluence 12.6 J/cm 2.52 log CFU/ml (2009) Apple cider E. coli ATCC 25922 2.32 log CFU/ml E. coli O157:H7 3.22 log CFU/ml Apple juice E. coli 3 pulses/s (pulse width 360 µs) of 100–1100 nm width, 4 log CFU/ml Pataro et al. (2011) 2 2 L. innocua approximately, 1.21 J/cm /pulse: PL fluence of 4 J/cm 2.98 log CFU/ml Orange juice E. coli 2.9 log CFU/ml L. innocua 0.93 log CFU/ml E. coli Fluence of 6 J/cm 2.02 log CFU/g L. innocua 1.77 log CFU/g Sugar syrup B. subtilis spores Pulses (250 µs): fluence 1.5 J/cm 4.2 log CFU/ml Chaine et al. (2012) S. cerevisiae Fluence 1.23 J/cm 5.4 log CFU/ml G. stearothermophilus spores Fluence 1.86 J/cm >4 log CFU/ml A. acidoterrestris spores 3 log CFU/ml A. niger Fluence 1.2 J/cm 1.3 log CFU/ml Infant food L. monocytogenes Width 1.5 µs; operating time 0–600 s; 2300 µs 1 log CFU/g Choi et al. (2010) treatment 4700 µs of treatment 2 log CFU/g 9500 µs of treatment 3 log CFU/g Milk E. coli 200–1100 nm, 3 Hz and 360 µs, 1.17 J/cm /pulse at a 0.61–1.06 log CFU/ Palgan et al. (2011) distance of 2.5 cm: 7–28 J/cm ml L. innocua 0.51–0.84 log CFU/ ml S. Thyphimurium 0.51–1.73 log CFU/ cm sublethal injury of S. cerevisiae cells at low doses up to 12 J/cm In contrast, PL did not cause any sublethal damage to the bacterial (Ferrario et al., 2014). PL treatment causes sublethal damages which cells such as E. coli, L. monocytogenes, S. Typhimurium, and V. make cells more sensitive to stress in subsequent stages such as parahaemolyticus (Hierro et al., 2012). Listeria and Salmonella were storage at low temperature (Lasagabaster and de Marañón, 2014). not found to have the ability to repair the cell damage induced by 192 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 PL through photoreactivation mechanism (Paskeviciute et al., 2011). Hence, foods with high carbohydrates but poor in fats and proteins, Sublethal damage of bacteria cells by PL treatment confirmed that such as fruits and vegetables, seem to be more appropriate for IPL membrane damage is one of the important causes for bacterial processing (Gómez-Lopez et al., 2005). inactivation, apart from microbial DNA damage, depending on the Continuous flow-through PL of apple juice was more effective energy dose and sensitivity of light pulses (Pataro et al., 2011). in inactivating microbes than batch mode PL (Muñoz et  al., 2012; Additionally, distance of the sample from the light source, treat- Ferrario et  al., 2013; Ferrario and Guerrero, 2016). Chaine et  al. ment time, volume of the sample, geometry of the treatment cham- (2012) mentioned that PL requires shorter residence time for micro- ber, orientation, and design of lamps are also the critical factors that bial inactivation and subsequently higher flows of liquid foods could are to be optimized in order to accomplish maximum effectiveness of be treated using various parallel modules of PL treatment. In apple the PL treatment (Gomez-Lopez et al., 2007; Krishnamurthy et al., juice, a maximum reduction of 7.29 log CFU/ml was achieved for 2007; Ignat et al., 2014; Xu and Wu, 2016). Inactivation effects of E. coli with high turbulence (3000 rpm) compared to 4.46 and 2.66 IPL treatment on L. monocytogenes showed significant inactivation log CFU/ml for the treatment with low turbulence (500  rpm) and compared to UV-C treatment due to higher penetration depth and static treatment, respectively. For the same high turbulence treat- emission power of IPL (Cheigh et al., 2013). Food parameters that ment, inactivation levels of E.  coli in apple cider of up to 5.49 log influence PL effectiveness for microbial inactivation are reflection CFU/ml greater than low turbulence and about 3.2 log CFU/ml coefficient, intrinsic transparency and surface condition of the item, higher than static treatment was observed by Sauer and Moraru thickness, colour, viscosity, moisture content, turbidity, light trans- (2009). The use of turbulence enhanced the inactivation of E. coli in missivity, the presence of particulate material, and flow conditions reconstituted milk by PL treatment (Miller et  al., 2012). Thus, tur- of the product (Choi et al., 2010; Artíguez et al., 2011; Ferrario and bulence can significantly enhance the effectiveness of PL treatment, Guerrero, 2016). Indeed, physiochemical factors such as chemical presumably by maximizing exposure of microbial cells to the inci- composition, total soluble compounds, pH and light absorbance dent light and could also disintegrate the clusters/clumps of micro- (especially due to compounds as carotenoids) could potentially pro- bial cells that lead to increasing microbial inactivation. tect the microorganisms from the PL treatments, and thus differ- A high fluence of 26.25 J/cm resulted in 3.2 log reduction in ent microbial inactivation levels are achieved (Valdivia-Nájar et al., the total microbial count, and concomitantly, milk temperature 2017). As the total solids in reconstituted milk increased, reduction was increased to 55°C, which indicated a combined effect of pho- levels of E. coli decreased by 2.0, 0.62, and 0.45 log CFU for 9.8%, tochemical and photothermal damage of natural microflora by PL 25%, and 45% total solids, respectively. The effect of optical prop- in raw milk (Innocente et al., 2014). E. coli and L. innocua counts erties of beverages on P.  aeruginosa inactivation by IPL has been were decreased by ≥4.7 and 1.93 log CFU/ml in apple juice treated reported (Miller et al., 2012; Hwang et al., 2015). They found that with PL at 28 J/cm , and subsequent recovery of the cell was not beverages with higher transparency like apple juice, carbonated drink, observed even after 48 h (Palgan et al., 2011). Similarly, exposure of 2 2 and plum juice showed 7 log reductions with 12.17–24.35 J/cm , 17.5 kJ/m fluence, PL found to decrease L.  brevis population in whereas grape juice, milk, and coffee showed a lower reduction apple juice by 3 log cycle (Ignat et al., 2014). PL did not affect pH, value of 1–1.9 log CFU/ml with a fluence of 29.21 J/cm . Similarly, Brix, and non-enzymatic browning index, whereas it did slightly due to differences in transparency of the medium (1 mm thickness), affect the colour of apple juice (Muñoz et  al., 2012). Similarly, no lower inactivation levels of E. coli and L. innocua were also reported change in colour, soluble substances, and pH of the product was by Palgan et  al. (2011) in milk (1275.2) and orange juice (79.7) reported until 53.3 J/g PL treatment in apple juice (Maftei et al., when compared to apple juice (5.81) and maximum recovery diluent 2014). The results of the sensory studies conducted by Palgan et al. (0.74) with lower ɛ. (2011) on reconstituted apple juice exposed to PL at 28 J/cm flu- PL was more efficient in the apple juice system with lower tur - ence showed that there was no significant difference in terms of col- bidity compared to orange and strawberry juices suggesting that our, sweetness, odour, or acidity of apple juice, but lowest score was higher turbidity of juices diminishes the PL efficiency (Ferrario observed for flavour compared to either control or samples treated et  al., 2015a). Chaine et  al. (2012) also observed lower inactiva- with PL for a shorter time. tion of B.  subtilis spores in sugar syrup (3 log reduction than in distilled water—4.6 log reduction) after exposure to 1.8 J/cm , PL Effect of PL for Surface Decontamination under static conditions. They suggested that these differences in the of Foods light transmission in the UV-C region as the absorption coefficient of clear syrup at 254 nm resulted in 200-fold higher than that cor- Various solid food products are being decontaminated by PL responding to distilled water. Ferrario et  al. (2013) concluded that processing for producing safe food, which increases the shelf life PL effectiveness is negatively influenced by the higher absorbance of the products. Few of the examples are listed in Table 2. Log values of liquids in the UV-C region. Properties of food surface have reduction values of E. coli and L. innocua reported by Ramos- an impact on decontamination efficiency (Kramer et al., 2017). Choi Villarroel et al. (2014) showed that fresh-cut avocado treated at et al. (2010) found that inactivation of L. monocytogenes at 15 kV 305–1100 nm (2.74 and 1.35 log CFU/g, respectively) were higher in infant meal (dark-coloured viscous product with 14% carbohy- than those of samples treated at 400 to 1100 nm (0.83 and 0.68 drates and 85.98% water) was effective (3 log reduction at 4800 µs) log CFU/g, respectively), indicating the antibacterial effect of but lower than light-coloured, thin, infant beverage (5 log reduction UV component. Efficacy of PL treatment depends on the type of at 3500 µs) which is due to the product characteristics. PL treatment microbe, inoculum size, and inoculation site (Huang and Chen, efficiency was hindered by the presence of milk fat due to scattering 2014). Manzocco et al. (2014) studied the effect of inoculation site of light by fat globules (Miller et al., 2012). Increasing levels of oil by inoculating Salmonella enterica in the pasta dough before rolling and protein reduced the killing efficiency of IPL since proteins have into sheet and after sheeting. They observed that log reduction was high absorption at about 288 nm and above of the UV region, lipids lower in the case of S. enterica inoculated in the dough before also absorb UV, decreasing the effective radiation dose on microbes. sheeting (0.8 log reduction) when compared to that of inoculated Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 193 Table 2. The effect of PL treatment on surface decontamination of foods. Food product Microorganism Treatment Log reduction Reference Fresh-cut melon Enterobacteriaceae UV-C irradiance on melon cubes was 2.61 log CFU/g Manzocco et al. (2011) 2 2 20 W/m up to 10 min: fluence—1200 J/m Fluence—6000 J/m 2.32 log CFU/g Fluence—12 000 J/m 2.14 log CFU/g Fresh-cut E. coli Full spectrum (λ = 180–1100 nm): total 3.03 log CFU/g Ramos-Villarroel et al. mushrooms L. innocua fluence of 12 J/cm 2.66 log CFU/g (2012) E. coli Fluence of 6 J/cm 2.02 log CFU/g L. innocua 1.77 log CFU/g Plum B. cereus Illumination spectrum was broad (200– 1.4 log CFU/g Luksiene et al. (2012) Tomato 1000 nm) and had maximal emission at 1.5 log CFU/g Cauliflower 260 nm; duration of light pulse was 112 µs, 1.3 log CFU/g Sweet pepper frequency 5 Hz: UV light dose 5.4 J/cm 1.8 log CFU/g Strawberry 1.5 log CFU/g Ground caraway B. subtilis 200 to 1100 nm with pulse duration of 0.8 log CFU/ml Nicorescu et al. (2013) 2 2 Ground black pepper 300 µs: treatment of 10 J/cm (1 J/cm × 10 Ground red pepper flashes) 1 log CFU/ml Blueberries E. coli O157:H7 Wavelength of 180–1100 nm with pulse 3.8->6.7 log CFU/g Huang and Chen Salmonella rate of 3 pulses/s and pulse width of 360 µs 4.8–5.7 log CFU/g (2014) for 5–60 s: PL fluence of 5–56.1 J/cm Spinach L. innocua 180 to 1100 nm with 17% of UV light. dura- 1.85 log CFU/g Agüero et al. (2016) E. coli tion—0.3 µs and fluence—8 J/cm 1.72 log CFU/g Egg shells S. enterica subsp. 200 to 1100 nm, with 20% of UV-C, 8% in 5 log CFU/egg shell Lasagabaster et al. enterica serovar Typhimurium UV-B and 12% in UV-A: treatments fluence (2011) of 2.1 J/cm Beef carpaccio E. coli Duration of the pulse is 250 µs, 30% UV 0.6–1.2 log CFU/ Hierro et al. (2012) light, 30% infrared radiation and 40% vis- cm S. Typhimurium ible light: fluencies of 0.7–11.9 J/cm 0.3–1.0 log CFU/ cm L. monocytogenes 0.3–0.9 log CFU/ cm Tuna carpaccio V. parahaemolyticus 0.2–1.0 log CFU/ cm L. monocytogenes 0.2–0.7 log CFU/ cm Fish products P. phosphoreum High-intensity pulses of 325 µs duration 5 log CFU/cm Lasagabaster and De S. liquefaciens and wavelengths from 200 to 1100 nm, 3.9 log CFU/cm Marañón (2012) S. putrefaciens with about 20% of UV-C, 8% of UV-B, and 2.1 log CFU/cm B. thermosphacta 12% of UV-A region: one pulse fluence of <1 log CFU/cm Pseudomonas 0.053 J/cm L. innocua RTE meat products L. monocytogenes Pulse is delivered in 250 µs that correspond 1.01–1.61 log CFU/ Ganan et al. (2013) 2 2 dry-cured loin to a fluence of 0.7 J/cm : total fluence ap- cm S. Thyphimurium plied 0.7–11.9 J/cm 0.51–1.73 log CFU/ cm Salchichon L. monocytogenes 0.89–1.81 log CFU/ cm S. Thyphimurium 0.26–1.48 log CFU/ cm Shrimp fillets L. monocytogenes 1.75 mJ/cm /pulse; pulse duration-1.5 µs; 2.2–2.4 log CFU/g Cheigh et al., (2013) Salmon fillets frequency-5 Hz; fluence—6.3 to 12.1 J/cm 1.9–2.1 log CFU/g Flatfish fillets 1.7–1.9 log CFU/g on the surface of egg pasta after sheeting (2.5 log reduction). Dip- on the chicken surface (Paskeviciute et al., 2011). Contrarily, Chun inoculated produce was harder to be decontaminated than spot- et al. (2009) reported that at 8000 J/m dose of UV-C irradiation, inoculated ones due to infiltration of E. coli into the open surface 2.74 log reduction was achieved in L. monocytogenes on RTE ham, structures of the produce (Xu et al., 2013). In contrary, at 8000 J/ whereas it was only 2.02 and 1.72 log cycle for S. Typhimurium m dose of UV-C irradiation, 2.16 log reduction was achieved in E. and Campylobacter jejuni, respectively. Whereas, one log reduction coli on ready-to-eat (RTE) salad surface, where it was 2.57 log cycle of E. coli and L. monocytogenes was achieved at the 60-s treatment for L. monocytogenes (Chun et al., 2010). PL treatment did not of UV light at 8-cm distance in raw salmon fillets (Ozer and show any significant difference in susceptibility of pathogen and Demirci, 2006). Paškevičiūtė and Lukšienė (2009) concluded that mesophiles. At 5.4 J/cm fluence of UV light, reduction by 2 and 2.4 the reduction of bacterial viability on the surface of chicken was a log CFU/ml was observed for Listeria and Salmonella, respectively, function of the light dose when the distance from the light source, 194 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 impulse repetition rate, and the voltage were constant. Only 0.99 preserving the quality of fruits by reducing sample heating, uniform log reduction of P. aeruginosa was observed on sesame seeds when PL exposure, and physical removal of bacterial cells due to the IPL treatment was applied, whereas 7 log reduction was observed agitation of the water. Colour discolouration was coupled with in P. aeruginosa inoculated mineral water. This large difference sample heating when blueberries treated with dry PL at 30 and 60 s in reduction is mainly due to the matrix type: while all sides of (Huang and Chen, 2014). Thus, wet PL can be considered as one sesame seeds could not be exposed to IPL because of shadowing of the potential non-chemical alternatives to chlorine washing with effect. The irregular surface of sesame seeds protected the hidden higher efficacy and environmentally friendly process. To promote microorganisms from IPL so that microbial reduction would not the quality of vegetables, and also to avoid shadowing effect of increase regardless of the fluence applied (Hwang et al., 2017). PL, wet PL treatment was carried out by Xu et al. (2013) for fresh Likewise, Moreaua et al. (2011) noticed the reduced effectiveness produce like green onions. Wet PL treatment showed time-dependent of PL in the case of peppercorn decontamination with B. subtilis log reduction for spot-inoculated green onions. However, wet PL compared to that of decontamination on glass marbles that could treatment had no effect on time for dip-inoculated produce (<1.2 be attributed to the non-uniform surface of the spice, which caused log reduction). At 30- and 60-s dry PL treatment on green onions, an insufficient microbial reduction. The surface topology plays a quality in terms of softer and shrunken tissue, colour, and smell were major role in PL treatment, as microbes can lodge on irregular altered. Dry PL at 5 s was more effective than 60-s wet PL treatment surfaces and thus reducing that effect of PL in the target organism (>4 log reduction) for E. coli inactivation in green onions (Xu et al., (Sauer and Moraru, 2009). PL treated at 5.4 J/cm for raspberry 2013). Egg decontamination efficacy by PL could also depend on and strawberry inactivated E. coli by 3.0 and 2.3 log CFU/g and washing process before PL processing (Hierro et al., 2009). Higher Salmonella by 3.4 and 3.9 log CFU/g, respectively. Variation in the Salmonella decontamination was obtained in unwashed egg shells reduction of microbes on the surface of raspberry and strawberry than washed ones which can be due to damage of egg cuticle that in can be attributed to shadowing/shielding effect (Bialka and Demirci, turn provide a protective shielding against PL. Washing procedures 2008). Due to shadowing/shielding effect, microbes on rough (washing with soap and warm water followed by immersion in surface structures have the chance of being protected by PL, thus by 70% ethanol and posterior eggshell flaming) could cause damage hiding in the sub-surface structures (Nicorescu et al., 2013; Maftei to the cuticle and thus facilitate cell penetration into pores and et al., 2014). Salmonella and E. coli showed a higher reduction in therefore protect bacteria being affected by light. Hierro et al. (2009) blueberry (4.2 and 5.7 log reduction, respectively) compared to that mentioned that there was a 2.49 log reduction of S. enteritidis in on strawberry (2.1 and 1.9 log reduction, respectively) at 22.5 J/cm unwashed egg shells. In contrast, a 5 log reduction in Salmonella due to the different topographical surface of the berries. The pres- counts were observed in both washed and unwashed eggshells ence of achenes on strawberry could potentially shadow microor- treated at 2.1 J/cm fluence. Lasagabaster et al. (2011) used different ganisms from highly directional coherent PL beam from reaching washing procedure for eggshells (immersion in 70% ethanol) and its target leading to partial decontamination compared to the even concluded that washing had no effect on PL antimicrobial smooth skin of blueberries (Huang et al., 2017). Cauliflower being effectiveness on the surface of eggshells and even did not detect any the most irregular surfaced vegetable was less decontaminated by Salmonella penetration into egg content. Salmonella inoculated on PL than other fruits and vegetables, which is said to be due to the eggshell was found to have photoreactivation mechanism, and hence shielding effect of PL and thus the antimicrobial efficiency of PL Hierro et al. (2009) advised to store eggs that are PL treated away exhibited clear dependence on surface irregularity (Luksiene et al., from light. 2012). Koh et al. (2016a) studied the effect of cut type on fresh- Inactivation efficacy of PL was similar for both total bacterial cut cantaloupe treated with PL. They found that sphere samples count (TBC) and total yeast and mould count (TYMC) as reported had significantly lesser microbial count compared to cuboid and by Xu and Wu (2016). Whereas at the end of the 10-day storage, triangular prism-shaped sample, which is due to area/volume ratio TBC and TYMC counts were significantly higher in PL 30  s than of the sample. Higher the area/volume ratio causes more wounds those in PL 5 s and PL 15 s, however, which was considerably lower on the product, thus higher electrolyte leakage leading to increased than control. This greater number of microbes on PL 30 s may be microbial growth. A higher percentage of microbial inactivation because of structural damage of raspberry (softer texture) due to of 50% was observed for sphere-shaped samples compared to the longer PL treatment that benefits microbial growth and a surface cuboidal or triangular prism, which could also be due to decreased structure that affected the attachment of bacterial cells by protecting scattering light around the edges of the sphere and lower shielding the pathogenic bacteria (Xu and Wu, 2016). The use of PL had effect due to lower initial microbial load (Koh et al., 2016a). reduced the amount of inoculated yeast cells on carrot slices by Sample temperature was found to increase with an increase in about three to four cycles (Kaack and Lyager, 2007), whereas it was pulses number, treatment time, and sample distance from the lamp 1.6 log cycles in apple discs exposed to PL (Gómez et  al., 2012b), (Wambura and Verghese, 2011; Ferrario et  al., 2013). Wambura due to shielding of microorganisms by rough apple surface and and Verghese (2011) observed 6°C temperature increase for every internalization into apple tissue that could have a major influence on 10-s PUV treatment. Similarly, Ferrario et  al. (2013) also found the inactivation pattern (Moreira et  al., 2017). Similarly, reduction that temperature of fruit juice treated for 60  s with PL increased in the native microflora was lower than L.  innocua and E.  coli between 7.4 and 16.8°C. To dissipate the temperature changes inoculated on spinach when treated with PL due to internalization due to sample heating, incorporation of the cooling systems in of endogenous microorganisms. And the initial load of microflora the equipment, external water-ethylene glycol cooling system was also significantly reduced, showing high efficiency for coliforms can be adopted that limits the heating rate and final temperature and its development was limited during refrigerated storage (Agüero of the product (Pataro et  al., 2011). Huang and Chen (2014) and et al., 2016). PL processing showed its capability to decontaminate Huang et  al. (2015) approached to overcome this limitation of PL and promote higher microbial stability during storage, thus by using wet PL treatment that is submerging the raspberries and increasing shelf life of the product (Ignat et  al., 2014). During the blueberries in agitated water. This process provided the benefits of cold storage, the counts of L.  innocua on fresh-cut tomatoes that Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 195 were subjected to PL treatments did not significantly change through of treated chicken depend on the process parameters and showed first 12 days of storage, whereas the gradual increase of L. innocua UV dose of 5.1 J/cm at 38°C had no changes on raw meat flavour counts on the untreated tomato slices were observed just after 4 days and taste. PUV light treatment affected the tissue structure of ham (Valdivia-Nájar et  al., 2017). Application of PL led to significantly which could be due to the destruction of the network and changes lower mesophilic aerobic count during the 14-day storage period in myofibrillar proteins (Wambura and Verghese, 2011). Sensory compared to untreated apple (Moreira et  al., 2017). PL treatment evaluation of PL-treated ham showed that there was no alteration could inactivate microbial growth and hence, extended the shelf life in colour, flavour, appearance, and odour, whereas, for bologna, of treated samples by 8  days, as compared to untreated fresh-cut differences for odour and flavour were observed at higher fluences cantaloupe (Koh et al., 2016a). Vacuum-packaged and -unpackaged than 4.2 J/cm (Hierro et al., 2011). Similarly, Tomašević (2015) also chicken frankfurters did not have any effect on log reduction found that there was no alteration in appearance and total score of L.  monocytogenes (maximum of 1.9 log CFU/cm ) with UV values of beef samples treated with IPL. In contrary, Hierro et al. treatment for 60  s at 5  cm; however, it caused colour and quality (2012) conducted the sensory analysis and found that PL fluences of changes in the samples (Keklik et  al., 2009). Decontamination of 8.4 and 4.2 J/cm or lower did not affect the raw attributes such as L.  monocytogenes in vacuum-packaged ham (1.78 log CFU/ cm ) odour and colour of beef, and tuna carpaccio, respectively. However, 2 2 was higher than bologna (1.11 log CFU/ cm ) at 8.4 J/cm . PL-treated during shelf-life studies, beef and tuna carpaccio showed significant, vacuum-packaged ham extended the shelf life by an additional remarkable difference in colour and odour when treated with PL at 30 days compared to the only vacuum-packaged ham, but the shelf 4.2 J/cm and above. Changes in a* and b* values were observed life of bologna was not extended by PL (Hierro et al., 2011). for RTE loin samples compared to Salchichon along the 28 days Apples treated with PL were susceptible to surface browning storage when PL of 11.9 J/cm was applied. Colour parameters were when compared to untreated samples (Moreira et al., 2017). PL not dramatically modified by PL treatment in these RTE dry-cured induces degradation of biopolymers in cell wall, affects the pectin products, which may be attributed to the greater stability of the present in the cell wall, and cells appeared collapsed with ruptured cured pigments in comparison to those of fresh meat (Ganan et al., membranes and thus causing a rupture and folding of cell walls. This 2013). membrane damage would increase in enzymatic browning reactions Ultraviolet light is known to induce a range of adverse effects like polyphenol oxidase activity due to greater tissue damage and in food products due to the generation of free radicals through a loss of functional cell compartmentalization (Gómez et al., 2012b). wide variety of photochemical reactions, which can damage vita- Gómez et al. (2012a) also found changes in total profile analysis, mins, antioxidants, while also inducing lipid oxidation and colour dynamic, and creep behaviour on apple surface due to PL treatment changes (Koutchma, 2009). One of the disadvantages of continuous and storage period. The use of PL at high fluences (28 J/cm ) UV light is the induction of oxidation processes in meat, which after- dramatically affects the final quality of fresh-cut mushrooms, and ward changes its sensorial properties (Paškevičiūtė and Lukšienė, thermal damage due to high PL doses seems to cause dehydration 2009; Paskeviciute et al., 2011). Wambura and Verghese (2011) also and major textural modification. Enzymatic inactivation in reported that PUV light treatment induced oxidation process, thus PL-treated samples flashed at that high dosage was also observed by making sample rancid during the storage time. The extent of lipid Oms-Oliu et al. (2010a). Similarly, Koh et al. (2016b) noticed that a peroxidation was found to be higher for vacuum-packaged chicken decrease in the pH and an increase in acidity were more pronounced frankfurters than unpackaged ones when treated at mild (5  s at for untreated samples compared to PL-treated fresh-cut cantaloupes, 13 cm) and moderate (30 s at 8 cm) UV treatment conditions (Keklik throughout the storage. Even, Koh et al. (2016a,b) found that there et al., 2009). A slight increase in lipid peroxidation was observed in was no effect on total soluble solids of fresh-cut cantaloupe at 4 the chicken meat after high-power PL treatment, whereas organo- ± 1°C due to decreased respiration rate in chilled storage. Colour leptic properties such as smell, odour, flavour, taste, or colour was not negatively affected by PL treatment for fruits and vegetables changes had no effect under non-thermal treatment conditions. At (Luksiene et al., 2012; Ignat et al., 2014; Agüero et al., 2016; Koh et higher exposure dose (>5.4 J/cm ), thermal effects were induced al., 2016a). However, change in colour of the endive salad and fresh- and also changes in organoleptic properties of chicken breast meat cut avocados was more pronounced as the fluence applied intensified was noticed (Paskeviciute et  al., 2011). Lipid peroxidation in dry- (Kramer et al., 2015), leading to browning during storage and firmness fermented salami was not noticed immediately after PL treatment, was significantly affected (Ramos-Villarroel et al., 2011). In contrast, whereas in chicken breast meat, it was found immediately (Rajkovic PL had a positive effect on colour and appearance of mung bean et  al., 2017). Off-odour in PL-treated samples remained over the sprouts (Kramer et al., 2015). Raspberries treated with PL showed a 14-day storage period due to photophysical changes occurred on decrease in brightness and did not substantially change the redness fresh-cut apples, and overall quality of the PL-treated apple was of the fruit immediately after the treatment, but along the storage, lower than that of untreated ones (Moreira et al., 2017). Similarly, berries became darker red and decrease in brightness, and a similar fresh-cut melon submitted to UV-C light had a lesser degree of off- trend in the stability of firmness of the fruit was also observed (Xu flavour perception than that of the control during 14-day storage and Wu, 2016). Similarly, UV spectra affected the colour and texture time (Manzocco et al., 2011). Slight flavour changes were noted by on fresh-cut mushroom and cut avocados and therefore treating fresh Ignat et al. (2014) in apple slice exposed to a fluence of 17.5 kJ/cm produce with quality stabilizing agents (anti-browning and texture which was similar to those detected during 7-day storage of untreated stabilizers) before PL flashing can be recommended for extending ones. Lasagabaster et al. (2011) found that there was no significant the shelf life of a product (Ramos-Villarroel et al., 2012, 2014). A effect on rheological properties of egg and a slight burnt odour in higher dose of PL (>1.75 J/cm ) treatment had a slight effect on the the egg shell was noticed as a sensory parameter, which was also appearance, colour, and enhanced the formation of non-enzymatic not significant. Even, PUV treatment had no effect on egg quality browning products and in turn increase the oxidative stability of in terms of albumen height, eggshell strength, and the presence of egg pasta (Manzocco et al., 2014). Paskeviciute et al. (2011) and cuticle (Keklik et al., 2010). High doses of PL (>8.75 J/cm ) reduced Paškevičiūtė and Lukšienė (2009) mentioned that sensory properties Salmonella as a result of egg pasta heating or sample heating rather 196 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 than the germicidal effect of UV component of light and sensory cantaloupes lead to an increase in the total phenolics concentration assessors observed that the intensity of sulphur odour increased in and the antioxidant capacity, thereby improving the health-related samples exposed at 1.75 J/cm (Manzocco et al., 2014). In cheddar characteristic of the product (Agüero et al., 2016; Koh et al., 2016b). cheese, PL did not affect the colour and lipid peroxidation during High-power PL treatment did not affect the AAC in fruits and had a refrigerated condition, but panelists scored the PL-treated samples negligible effect on total phenolic content (TPC) in fresh fruits and lower than the untreated ones for the sensory attributes such as vegetables (Luksiene et al., 2012; Charles et al., 2013; Koh et al., overall liking, flavour, and appearance. However, a dose of 9.22 2016a). TPC was not affected right after the treatment, whereas dur- J/cm had an adverse effect on organoleptic properties of cheese ing 10-day storage it was found to be decreasing significantly and at (Proulx et al., 2017). Similarly, a significant difference in odour and the end of the storage, PL did not improve nor affect the TPC levels flavour in the cheese slices treated with 4.2 and 8.4 J/cm shows in raspberries (Xu and Wu, 2016). The total anthocyanin content the presence of sulphur notes and the difference in decontamination (TAC) of raspberry was not influenced by PL at 5 and 15 s; surpris- magnitude between types of cheese which could be explained by ingly, PL-treated berries showed higher TAC compared to the control their different topography that is porous nature in Manchego vs at the end of the 10-day storage. However, PL at 30 s increased the smooth in Gouda type of cheeses (Fernández et al., 2016). Gómez- TAC by 10.1 mg cyanidin-3-glucoside equivalents/100 g fruit, when Lopez et al. (2005) mentioned that the presence of sensory attributes compared to 5 s treatment which could be due to stimulation of such as off-odours in IPL-flashed minimally processed white cabbage colour and anthocyanin accumulation by PL (Xu and Wu, 2016). and overall visual quality in Iceberg lettuce limited the shelf life to 7 The respiration rate was increased by the production of CO and and 3 days, respectively. O consumption at a higher rate when PL was applied on spinach The PL treatment affected the textural properties, firmness and fresh-cut cantaloupe (Agüero et al., 2016; Koh et al., 2016a). of fruit and vegetables (Luksiene et al., 2012; Xu and Wu, 2016; Similarly, partial pressures of O and CO inside the packages of 2 2 Moreira et al., 2017). Firmness values reported by Ramos-Villarroel tomato slices were significantly affected by PL processing (Valdivia- et al. (2014) showed that fresh-cut avocado treated at 305–1100 Nájar et al., 2017). These changes could be associated with a physi- nm were lower than those of samples treated at 400–1100 nm over ological stress or even physiological damage caused by the IPL the entire 15-day storage period, although their differences were not treatment, which in turn could affect the metabolic activity of the statistically significant. The application of UV-C light on fresh-cut vegetable/fruit tissue (Agüero et al., 2016). IPL treatment increased melon had no differences in colour and firmness up to 3 days of stor - the respiration rate and gas concentration of lettuce and fresh-cut age as the leakage of intercellular liquids from UV-C light-treated mushroom at the end of the storage, and the O level was <2%, samples was significantly lower than the control. Thus, UV-C light indicating anaerobic respiration of product in turn affecting the sen- treatment appears to be capable of increasing the dehydration of a sory quality/properties of the product (Gómez-Lopez et al., 2005; thin surface layer of melon cubes without affecting its overall firm- Ramos-Villarroel et al., 2012). Likewise, during storage conditions, ness and odour. It can be inferred that this phenomenon may cause respiration rate of IPL-treated fresh-cut avocados increased and thus the formation of a thin dried film hindering juice leakage during caused an undesirable anaerobic condition leading to the fermenta- the first 3 days of storage (Manzocco et al., 2011). PL treatment tion process in the fruit or triggering anaerobic metabolism of the maintained the colour, firmness, and carotenoid content of fresh-cut stored product which in turn lead to increase in ethanol production mangoes (Charles et al., 2013). Strawberries treated with PL did not and inhibiting ethylene production (Ramos-Villarroel et al., 2011). show pronounced softening when compared to untreated samples In contrast, Oms-Oliu et al. (2010a), Koh et al. (2016b), and Kramer even after 8 days of storage at 6°C, and cell wall strengthening of et al. (2015) did not observe any significant effect of CO by PL the fruit was induced by PL stress (Duarte-Molina et al., 2016). application in fresh-cut mushrooms, cantaloupe, and mung bean Similarly, firmness retention was also observed on PL-treated fresh- sprouts, respectively. cut cantaloupe compared to untreated samples during the storage, which may be due to the thickness of the sample (~3 cm) as the Combination Processing With PL effect of PL is restricted to the surface of the product (Koh et al., 2016a,b). But contrarily, the adverse effect of single PL treatment at The limitations of PL processing are uneven exposure, shadowing 11.7 J/cm on tissue structure of fresh-cut cantaloupes under chilled effect, browning, and sample heating. Many technologies/strategies storage was minimized by applying repetitive PL (RPL) treatment have been developed to address and challenge the limits of process- at 0.9 J/cm every 48-h interval leading to increased microbiologi- ing, increase the inactivation efficacy, maintain the quality of foods, cal quality, retention of firmness, and ascorbic acid content (AAC). and finally obtain minimally processed foods (Señorans et al., 2003). Further more, firmness was higher for fresh-cut cantaloupes treated Application of an anti-browning dipping treatment in combination with RPL compared to the untreated fresh-cut cantaloupes through- with IPL would increase the shelf life of minimally processed vegeta- out storage that may be due to lower CO concentration in treated bles and fruits (Gómez-Lopez et al., 2005). The use of ascorbic acid samples that could otherwise decompartmentalize the enzyme and (AC) at 1% on sliced mushroom before flashing at 4.8 and 12 J/cm their substrates which then act on cell walls of fruits tissue leading to significantly reduced browning during storage (Oms-Oliu et al., rapid deterioration (Koh et al., 2016b). 2010). To minimize the browning on PL-irradiated apple surface, PL treatment did not have any effect on the antioxidant activity AC/calcium chloride solution was used as an anti-browning of fruits and vegetables (Luksiene et al., 2012; Moreira et al., 2017). dipping prior to PL treatment (Gómez et al., 2012a). Further, this AAC was conserved throughout the storage period when treated at combination of AC + PL–treated apples showed greater microbial low fluences (2.7 and 7.8 J/cm ) in fresh-cut cantaloupe (Koh et al., growth after 7-day refrigerated storage than PL alone which could 2016a). A slight increase in AAC after RPL treatment was noticed be due to tissue damage and antioxidant capacity of AC that affect and even maintained throughout the storage, which could be due the damage caused by PL on microbes. In a similar study conducted to abiotic stress exerted by PL irradiation on fresh-cut cantaloupes by Moreira et al. (2017), pectin-coated fresh-cut apples that were (Koh et al., 2016b). IPL applied on spinach and RPL on fresh-cut exposed to PL were found to have the highest reduction in the Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 197 microbial count during storage, but the combination was not found application of US and PL was extended throughout storage com- to be antagonistic. The combined application of the edible coating pared to fresh untreated juice (Ferrario et al., 2015b). [gellan-gum–based (0.5% w/v) coating enriched with apple fibre] and The sequence of high-intense pulsed light (HIPL)/PEF resulted PL (12 J/cm ) treatment retarded the microbiological deterioration in a slight lowering of E.  coli K12 cells in apple juice compared of fresh-cut apples, reduced softening, and browning during 14 to PEF/HIPL, and the combination had no effect on quality days of storage at 4°C (Moreira et al., 2015). Dipping of fresh-cut parameters except for slight colour changes. HIPL/PEF treatment apples in AC/calcium chloride solution preceding to pectin coating had a significant effect on sensory attributes such as flavour and followed by PL treatment was more efficient in minimizing and odour of the non-thermally treated apple juice compared to browning, retaining antioxidant activity, and even did not have any thermally pasteurized control (Caminiti et  al., 2011b). Caminiti effect on microbial loads and sensory acceptability of apple cubes. et  al. (2011a) reported that light-based technology (UV/HIPL) Firmness was also maintained in fresh-cut apples when treated combined with PEF had no effect on colour, flavour, non-enzymatic with AC/calcium chloride solution that would help in cross-linking browning, TPC, and TAC of an apple and cranberry juice blend the polymer matrix and thus delaying softening of apple surfaces and received similar sensory score to that of pasteurized samples, (Moreira et al., 2017). The treatments combining PL (12 J/cm ) and whereas combination with manothermosonication (MTS) malic acid (MA) of 2% v/v resulted in significantly greater inhibition adversely affected overall acceptability and product quality. of L. innocua and E. coli populations than either PL or MA alone, Similarly, Caminiti et  al. (2012) found no change in colour, by achieving more than 5 log reductions for fresh produces such browning, and anthocyanin content of orange and carrot juice 2 2 as fresh-cut avocado, watermelon, and mushroom throughout the blend treated with either PEF, UV (10.6 J/cm ) or HIPL (3.3 J/cm ), storage period. Even, TEM observations demonstrated that damage, with MTS (400 kPa, 35°C, 1000 W, 20 kHz). Muñoz et al. (2011) especially to E. coli cells, was caused by a combination of treatments concluded that HIPL and thermosonication (TS) in combination due to agglutination of cytoplasmic content and disruption of cell irrespective of the sequence applied had an additive effect on E. coli membrane thus leading to microbial death (Ramos-Villarroel et al., inactivation in orange juices when compared to either of the technol- 2015). The combination of PL and MA dipping of mango slices ogy as a stand-alone. US in conjunction with PL treatment exhibited was found to be additive leading to a maximum reduction of 4.49 an inactivation equal to the sum of both effects taken separately (6.3, log cycle for L. innocua compared to PL alone (2.5 log CFU/g). It 5.9, and 3.7 log reduction for S. enteritidis, E. coli, and S. cerevisiae, is noteworthy that combination of PL, MA, and alginate coating respectively) in commercial apple juice. Delay in mould and yeast (ALC) lowered the inactivation level at the same time, and ALC acted recovery was observed due to the additive effect of US + PL during as an antagonistic factor which limited the effect of MA and PL. the 10-day storage period and prevented apple juice from turning Therefore, Salinas-Roca et al. (2016) concluded that PL should be darker and brownish (Ferrario and Guerrero, 2016). The combina- applied before ALC and MA treatment to overcome the interference tion of PL (low fluence—51.5 J/ml) as a first hurdle followed by TS caused by ALC. And, the highest inactivation of moulds, yeast, and led to significantly higher inactivation of E. coli than TS as the first psychrophilic bacteria was obtained with PL–ALC–MA treatment hurdle. The combination of PL and TS showed an additive effect on that showed the best microbial quality of mango slices during the inactivation of E.  coli than any of these hurdles applied individual storage, and also ALC helped to maintain the integrity of fruit by which could be due to the influence of treatment on different targets reducing the presence of exudates. that is DNA for PL and cell membrane for TS (Muñoz et al., 2012). Maftei et  al. (2014) stated that studies should be aimed at Muñoz et al. (2011) reported that there was no evidence of sublethal evaluating strategies based on the combination of PL treatments damage of cells with HIPL and TS applied individually or in com- with other minimal processing technologies, e.g. addition of natu- bination, but sublethal injury was detected by Muñoz et al. (2012) ral preservatives or mild heat treatment, in order to successfully when PL (low—4.03 J/cm ) was applied as the first hurdle with TS tackle safety issues for clarified juices treated with PL technology. compared to PL (high—5.1 J/cm ) treatment as a first hurdle. Combined effect of PL + nisin treatment in RTE sausages, resulted The combination of wet PL and 1% H O was found to be 2 2 in a significantly higher reduction of L.  innocua compared with the most efficient treatment for inactivating Salmonella on individual treatment (PL alone—1.37 and nisin dip alone—2.35 log raspberries and blueberries by >5.6 log CFU/g (Huang et al., CFU), thus suggesting an additive effect of PL and nisin of 4.03 log 2015). Dip-inoculated green onions were treated using PL (60 s), CFU (Uesugi and Moraru, 2009). Non-thermal PL treatment inacti- surfactant (sodium dodecyl sulphate, SDS)–sanitizer combination vation tests against L. innocua inoculated on modified chitosan con- washing (10 ppm chlorine + 1000 ppm SDS and 300 ppm H O 2 2 taining a nanoemulsion of mandarin essential oil-coated green beans + 1000 ppm SDS) as well as PL–surfactant–sanitizer combination 5 2 showed that 1.2 × 10 J/m per bean side was able to cause a reduc- (10 ppm chlorine + 1000 ppm SDS + 60 s PL and 300 ppm H O 2 2 tion of about 2 log cycles. However, PL did not show any synergistic + 1000 ppm SDS + 60 s PL). Different inactivation efficiency has antimicrobial effect against L. innocua throughout the storage and been observed in various structures of green onions (Figure 5). colour properties had a slight detrimental impact with browning The combination of wet PL treatment with chlorine washing spots formation on the samples (Donsì et al., 2015). Furthermore, a had an additive effect on E. coli inactivation of about 2.4 log 6 log cycle in yeast reduction was observed by Ferrario et al. (2015b) reduction when compared to chlorine washing or PL alone. PL when PL was applied prior to US treatment for both commercial combined with SDS; surfactant was better effective compared and naturally squeezed apple juice. Similarly, Ferrario and Guerrero to PL and chlorine combination showing the synergistic effect (2017) also achieved S.  cerevisiae KE 162 inactivation of 5.8 and of surfactant. Hydrogen peroxide was slightly more efficient in 6.4 log reduction in commercial and naturally squeezed apple juice inactivation of E. coli on green onions (0.7 to 2.6 log CFU/g) respectively, even though US treatment was applied before PL. than thymol and citric acid combined with 60 s PL treatment. Whereas, US applied before PL treatment did not contribute signifi- PL–surfactant–sanitizer combination had no additive effect when cant inactivation for A.  acidoterrestris spore in apple juice matrix. compared to PL plus surfactant combination (Xu et al., 2013). These combinations showed an additive effect on inactivation and PL is more efficient in reducing microbial loads on a fresh-cut storage studies revealed that the level of inactivation reached by the salad than similar treatments in electrolyzed water (400 ppm free 198 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 Figure 5. Combined effect of PL–surfactant–sanitizer on the inactivation of E. coli O157:H7 on dip-inoculated green onions. The initial populations of E. coli O157:H7 for dip inoculated stems and leaves were 4.5 and 5.5 log10 CFU/g, respectively. Values in stems group marked by the same capital letter were not significantly different (P > 0.05). Values in leaves group marked by the same lowercase letter were not significantly different (P > 0.05) (Xu et al., 2013). chlorine) or chlorine dioxide (15 ppm). PL may, therefore, be as physical and chemical properties of the liquid foods affects the an appropriate measure to reduce the required amount of fresh occurrence of lethal and sublethal effects induced by PL treatment. water in fresh produce processing and to keep microbial loads in the wash water on a low level (Kramer et al., 2017). Therefore, PL Acknowledgement in combination with other technologies can be a novel technology The authors thank the Director, CSIR-CFTRI, Mysore, India. M.L. Bhavya for producing minimally processed foods without compromising thank UGC, New Delhi for UGC-NET fellowship. the nutritional and sensorial quality of foods. Conflict of interest statement. None declared. Conclusion References PL being one among the novel food-processing techniques has the Agüero, M. V., Jagus, R. J., Martín-Belloso, O., Soliva-Fortuny, R. (2016). ability to reduce the deleterious effects that thermal processing and Surface decontamination of spinach by intense pulsed light treatments: traditional processing methods have on the colour, texture, flavour, Impact on quality attributes. Postharvest Biology and Technology 121: and nutritive value of foods. The novel emerging PL technology 118–125. is finding application in the food industry with a broad scope in Anderson, J. G., Rowan, N. J., MacGregor, S. J., Fouracre, R. A., Farish, O. improving nutritional and organoleptic properties and also extend- (2000). Inactivation of food-borne enteropathogenic bacteria and spoilage ing shelf life of food. Novel technologies are considered to be a fungi using pulsed-light. IEEE Transactions on Plasma Science 28: 83–88. very promising alternative to conventional processing techniques. Artíguez, M. L., Lasagabaster, A., de Marañón, I. M. (2011). Factors affecting microbial inactivation by pulsed light in a continuous flow-through unit A distinct advantage of light-based techniques for certain operating for liquid products treatment. Procedia Food Science 1: 786–791. parameters is the inactivation of microorganisms with maintaining Bialka, K. L., Demirci, A. (2007). Decontamination of Escherichia coli of the foods’ sensory attributes and minimal quality loss. One of the O157:H7 and Salmonella enterica on blueberries using ozone and pulsed disadvantages of PL is high investment costs (€300 000–800 000) UV-light. Journal of Food Science 72: M391–M396. and PL is an inappropriate technology for cereals, grains, and spices Bialka, K. L., Demirci, A. (2008). Efficacy of pulsed UV-light for the due to their opaque nature, uneven surfaces, crevices, or pores decontamination of Escherichia coli O157:H7 and Salmonella spp. on because of the ability of microorganisms to harbour in minor open- raspberries and strawberries. Journal of Food Science 73: M201–M207. ings, whereas it is an efficient method of decontaminating packag- Bialka, K. L., Demirci, A., Puri, V. M. (2008). Modeling the inactivation of ing materials, surface of foods and liquids. Therefore, light-based Escherichia coli O157: H7 and Salmonella enterica on raspberries and technology with slight alteration by the addition of cooling systems strawberries resulting from exposure to ozone or pulsed UV-light. Journal of Food Engineering 85: 444–449. in order to minimize the thermal effect can be a promising technique Caminiti, I. M., Noci, F., Morgan, D. J., Cronin, D. A., Lyng, J. G. (2012). to inactivate the microbes in plant-derived foods, including both The effect of pulsed electric fields, ultraviolet light or high intensity light solid and liquids by retaining the quality of foods and increasing pulses in combination with manothermosonication on selected physico- the shelf life of the products. And, light-based processing of animal chemical and sensory attributes of an orange and carrot juice blend. Food products with proper packaging material has an application in the and Biproducts Processing 90: 442–448. food industry by increasing the shelf life and even maintaining the Caminiti, I. M., et al. (2011a). Impact of selected combinations of non-thermal organoleptic properties of food throughout the storage. In future, processing technologies on the quality of an apple and cranberry juice more research is required for a more comprehensive understand- blend. Food Chemistry 124: 1387–1392. ing of inactivation mechanism of Gram-positive and Gram-negative Caminiti, I. M., et  al. (2011b). The effect of pulsed electric fields (PEF) in bacteria by PL, how the fluence, type of microbial strain, as well combination with high intensity light pulses (HILP) on Escherichia coli Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 199 inactivation and quality attributes in apple juice. Innovative Food Science Ferrario, M., Guerrero, S., Alzamora, S. M. (2014). Study of pulsed light- and Emerging Technologies 12: 118–123. induced damage on Saccharomyces cerevisiae in apple juice by flow Chaine, A., Levy, C., Lacour, B., Riedel, C., Carlin, F. (2012). Decontamination cytometry and transmission electron microscopy. Food and Bioprocess of sugar syrup by pulsed light. Journal of Food Protection 75: 913–917. Technology 7: 1001–1011. Charles, F., Vidal, V., Olive, F., Filgueiras, H., Sallanon, H. (2013). Pulsed light Fine, F., Gervais, P. (2004). Efficiency of pulsed UV light for microbial treatment as new method to maintain physical and nutritional quality of decontamination of food powders. Journal of Food Protection 67: 787– fresh-cut mangoes. Innovative Food Science and Emerging Technologies 792. 18: 190–195. Food and Drug Administration. (1996). Pulsed Light for the Treatment of Chawla, R., Patil, G. R., Singh, A. K. (2011). High hydrostatic pressure Food, 21CFR179.4. technology in dairy processing: A  review. Journal of Food Science and Ganan, M., Hierro, E., Hospital, X. F., Barroso, E., Fernández, M. (2013). Use Technology 48: 260–268. of pulsed light to increase the safety of ready-to-eat cured meat products. Cheigh, C. I., Hwang, H. J., Chung, M. S. (2013). Intense pulsed light (IPL) and Food Control 32: 512–517. UV-C treatments for inactivating Listeria monocytogenes on solid medium Gómez, P. L., García-Loredo, A., Nieto, A., Salvatori, D. M., Guerrero, and seafoods. Food Research International 54: 745–752. S., Alzamora, S. M. (2012a). Effect of pulsed light combined with an Cheigh, C. I., Park, M. H., Chung, M. S., Shin, J. K., Park, Y. S. (2012). antibrowning pretreatment on quality of fresh cut apple. Innovative Food Comparison of intense pulsed light-and ultraviolet (UVC)-induced cell Science and Emerging Technologies 16: 102–112. damage in Listeria monocytogenes and Escherichia coli O157: H7. Food Gómez, P. L., Salvatori, D. M., García-Loredo, A., Alzamora, S. M. (2012b). Control 25: 654–659. Pulsed light treatment of cut apple: Dose effect on color, structure, and Choi, M. S., Cheigh, C. I., Jeong, E. A., Shin, J. K., Chung, M. S. (2010). microbiological stability. Food and Bioprocess Technology 5: 2311–2322. Nonthermal sterilization of Listeria monocytogenes in infant foods by Gómez-López, V. M., Devlieghere, F., Bonduelle, V., Debevere, J. (2005). Intense intense pulsed-light treatment. Journal of Food Engineering 97: 504–509. light pulses decontamination of minimally processed vegetables and their Chun, H. H., Kim, J. Y., Song, K. B. (2010). Inactivation of foodborne shelf-life. International Journal of Food Microbiology 103: 79–89. pathogens in ready-to-eat salad using UV-C irradiation. Food Science and Gomez-Lopez, V. M., Ragaert, P., Debevere, J., Devlieghere, F. (2007). Pulsed Biotechnology 19: 547–551. light for food decontamination: a  review. Trends in Food Science and Chun, H., Kim, J., Chung, K., Won, M., Song, K. B. (2009). Inactivation kinetics Technology 18: 464–473. of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Hierro, E., Barroso, E., De la Hoz, L., Ordóñez, J. A., Manzano, S., Fernández, Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation. M. (2011). Efficacy of pulsed light for shelf-life extension and inactivation Meat Science 83: 599–603. of Listeria monocytogenes on ready-to-eat cooked meat products. Devlieghere, F., Vermeiren, L., Debevere, J. (2004). New preservation Innovative Food Science and Emerging Technologies 12: 275–281. technologies: possibilities and limitations. International Dairy Journal 14: Hierro, E., Ganan, M., Barroso, E., Fernández, M. (2012). Pulsed light 273–285. treatment for the inactivation of selected pathogens and the shelf-life Donsì, F., et al. (2015). Green beans preservation by combination of a modified extension of beef and tuna carpaccio. International Journal of Food chitosan based-coating containing nanoemulsion of mandarin essential oil Microbiology 158: 42–48. with high pressure or pulsed light processing. Postharvest Biology and Hierro, E., Manzano, S., Ordóñez, J. A., de la Hoz, L., Fernández, M. (2009). Technology 106: 21–32. Inactivation of Salmonella enterica serovar enteritidis on shell eggs by Duarte-Molina, F., Gómez, P. L., Castro, M. A., Alzamora, S. M. (2016). pulsed light technology. International Journal of Food Microbiology 135: Storage quality of strawberry fruit treated by pulsed light: Fungal decay, 125–130. water loss and mechanical properties. Innovative Food Science and Hilton, S. T., de Moraes, J. O., Moraru, C. I. (2017). Effect of sublethal Emerging Technologies 34: 267–274. temperatures on pulsed light inactivation of bacteria. Innovative Food Dunn, J., Ott, T., Clark, W. (1995). Pulsed-light treatment of food and Science and Emerging Technologies 39: 49–54. packaging. Food Technology 49: 95–98. Huang, Y., Chen, H. (2014). A novel water-assisted pulsed light processing for Elmnasser, N., Guillou, S., Leroi, F., Orange, N., Bakhrouf, A., Federighi, M. decontamination of blueberries. Food Microbiology 40: 1–8. (2007). Pulsed-light system as a novel food decontamination technology: Huang, Y., Sido, R., Huang, R., Chen, H. (2015). Application of water-assisted A review. Canadian Journal of Microbiology 53: 813–821. pulsed light treatment to decontaminate raspberries and blueberries from Fernández, M., Arias, K., Hierro, E. (2016). Application of pulsed light to sliced Salmonella. International Journal of Food Microbiology 208: 43–50. cheese: Effect on listeria. Food and Bioprocess Technology 9: 1335–1344. Huang, Y., Ye, M., Cao, X., Chen, H. (2017). Pulsed light inactivation of Ferrario, M., Alzamora, S. M., Guerrero, S. (2013). Inactivation kinetics of murine norovirus, Tulane virus, Escherichia coli O157:H7 and Salmonella some microorganisms in apple, melon, orange and strawberry juices by in suspension and on berry surfaces. Food Microbiology 61: 1–4. high intensity light pulses. Journal of Food Engineering 118: 302–311. Hwang, H. J., Cheigh, C. I., Chung, M. S. (2015). Relationship between optical Ferrario, M., Alzamora, S. M., Guerrero, S. (2015a). Study of pulsed light properties of beverages and microbial inactivation by intense pulsed light. inactivation and growth dynamics during storage of Escherichia coli Innovative Food Science and Emerging Technologies 31: 91–96. ATCC 35218, Listeria innocua ATCC 33090, Salmonella enteritidis Hwang, H. J., Cheigh, C. I., Chung, M. S. (2017). Construction of a pilot-scale MA44 and Saccharomyces cerevisiae KE162 and native flora in apple, continuous-flow intense pulsed light system and its efficacy in sterilizing orange and strawberry juices. International Journal of Food Science and sesame seeds. Innovative Food Science and Emerging Technologies 39: Technology 50: 2498–2507. 1–6. Ferrario, M., Alzamora, S. M., Guerrero, S. (2015b). Study of the inactivation Ignat, A., Manzocco, L., Maifreni, M., Bartolomeoli, I., Nicoli, M. C. (2014). of spoilage microorganisms in apple juice by pulsed light and ultrasound. Surface decontamination of fresh-cut apple by pulsed light: Effects Food Microbiology 46: 635–642. on structure, colour and sensory properties. Postharvest Biology and Ferrario, M., Guerrero, S. (2016). Effect of a continuous flow-through pulsed Technology 91: 122–127. light system combined with ultrasound on microbial survivability, color Innocente, N., et  al. (2014). Effect of pulsed light on total microbial count and sensory shelf life of apple juice. Innovative Food Science and Emerging and alkaline phosphatase activity of raw milk. International Dairy Journal Technologies 34: 214–224. 39: 108–112. Ferrario, M., Guerrero, S. (2017). Impact of a combined processing technology Kaack, K., Lyager, B. (2007). Treatment of slices from carrot (Daucus carota) involving ultrasound and pulsed light on structural and physiological using high intensity white pulsed light. European Food Research and changes of Saccharomyces cerevisiae KE 162 in apple juice. Food Technology 224: 561–566. Microbiology 65: 83–94. Keklik, N. M., Demirci, A., Puri, V. M. (2009). Inactivation of Listeria monocytogenes on unpackaged and vacuum-packaged chicken 200 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 frankfurters using pulsed UV-light. Journal of Food Science 74: M431– Moreira, M. R., Álvarez, M. V., Martín-Belloso, O., Soliva-Fortuny, R. (2017). M439. Effects of pulsed light treatments and pectin edible coatings on the quality Keklik, N. M., Demirci, A., Patterson, P. H., Puri, V. M. (2010). Pulsed UV light of fresh-cut apples: A hurdle technology approach. Journal of the Science inactivation of Salmonella enteritidis on eggshells and its effects on egg of Food and Agriculture 97: 261–268. quality. Journal of Food Protection 73: 1408–1415. Moreira, M. R., Tomadoni, B., Martín-Belloso, O., Soliva-Fortuny, R. (2015). Koh, P. C., Noranizan, M. A., Karim, R., Nur Hanani, Z. A. (2016a). Preservation of fresh-cut apple quality attributes by pulsed light in Microbiological stability and quality of pulsed light treated cantaloupe combination with gellan gum-based prebiotic edible coatings. LWT-Food (Cucumis melo L. reticulatus cv. Glamour) based on cut type and light Science and Technology 64: 1130–1137. fluence. Journal of Food Science and Technology 53: 1798–1810. Muñoz, A., et al. (2012). Effects on Escherichia coli inactivation and quality Koh, P. C., Noranizan, M. A., Karim, R., Hanani, Z. A. N. (2016b). Repetitive attributes in apple juice treated by combinations of pulsed light and pulsed light treatment at certain interval on fresh-cut cantaloupe (Cucumis thermosonication. Food Research International 45: 299–305. melo L. reticulatus cv. Glamour). Innovative Food Science and Emerging Muñoz, A., et  al. (2011). Combinations of high intensity light pulses and Technologies 36: 92–103. thermosonication for the inactivation of Escherichia coli in orange juice. Koutchma, T. (2009). Advances in ultraviolet light technology for non-thermal Food Microbiology 28: 1200–1204. processing of liquid foods. Food and Bioprocess Technology 2: 138–155. Nicorescu, I., Nguyen, B., Moreau-Ferret, M., Agoulon, A., Chevalier, S., Kramer, B., Wunderlich, J., Muranyi, P. (2015). Pulsed light decontamination of Orange, N. (2013). Pulsed light inactivation of Bacillus subtilis vegetative endive salad and mung bean sprouts and impact on color and respiration cells in suspensions and spices. Food Control 31: 151–157. activity. Journal of Food Protection 78: 340–348. Norton, T., Sun, D. W. (2008). Recent advances in the use of high pressure as an Kramer, B., Wunderlich, J., Muranyi, P. (2017). Pulsed light decontamination effective processing technique in the food industry. Food and Bioprocess of endive salad and mung bean sprouts in water. Food Control 73: 367– Technology 1: 2–34. 371. Oms-Oliu, G., Aguiló-Aguayo, I., Martín-Belloso, O., Soliva-Fortuny, R. Krishnamurthy, K., Demirci, A., Irudayaraj, J. M. (2007). Inactivation of (2010a). Effects of pulsed light treatments on quality and antioxidant Staphylococcus aureus in milk using flow-through pulsed UV-light properties of fresh-cut mushrooms (Agaricus bisporus). Postharvest treatment system. Journal of Food Science 72: M233–M239. Biology and Technology 56: 216–222. Krishnamurthy, K., Tewari, J. C., Irudayaraj, J., Demirci, A. (2010). Microscopic Oms-Oliu, G., Martín-Belloso, O., Soliva-Fortuny, R. (2010b). Pulsed and spectroscopic evaluation of inactivation of Staphylococcus aureus by light treatments for food preservation. A  review. Food and Bioprocess pulsed UV light and infrared heating. Food and Bioprocess Technology Technology 3: 13. 3: 93. Orlowska, M., Koutchma, T., Grapperhaus, M., Gallagher, J., Schaefer, R., Lasagabaster, A., de Marañón, I. M. (2012). Sensitivity to pulsed light Defelice, C. (2013). Continuous and pulsed ultraviolet light for nonthermal technology of several spoilage and pathogenic bacteria isolated from fish treatment of liquid foods. Part 1: Effects on quality of fructose solution, products. Journal of Food Protection 75: 2039–2044. apple juice, and milk. Food and Bioprocess Technology 6: 1580–1592. Lasagabaster, A., de Marañón, I. M. (2014). Survival and growth of Listeria Ortega-Rivas, E., Salmerón-Ochoa, I. (2014). Nonthermal food processing innocua treated by pulsed light technology: Impact of post-treatment alternatives and their effects on taste and flavor compounds of beverages. temperature and illumination conditions. Food Microbiology 41: 76–81. Critical Reviews in Food Science and Nutrition 54: 190–207. Lasagabaster, A., Arboleya, J. C., De Maranon, I. M. (2011). Pulsed light Otaki, M., Okuda, A., Tajima, K., Iwasaki, T., Kinoshita, S., Ohgaki, S. (2003). technology for surface decontamination of eggs: Impact on Salmonella Inactivation differences of microorganisms by low pressure UV and pulsed inactivation and egg quality. Innovative Food Science and Emerging Tech- xenon lamps. Water Science and Technology 47: 185–190. nologies 12: 124–128. Ozer, N. P., Demirci, A. (2006). Inactivation of Escherichia coli O157: H7 Levy, C., Aubert, X., Lacour, B., Carlin, F. (2012). Relevant factors affecting and Listeria monocytogenes inoculated on raw salmon fillets by pulsed microbial surface decontamination by pulsed light. International Journal UV-light treatment. International Journal of Food Science and Technology of Food Microbiology 152: 168–174. 41: 354–360. Luksiene, Z., Buchovec, I., Kairyte, K., Paskeviciute, E., Viskelis, P. (2012). Palgan, I., et  al. (2011). Effectiveness of high intensity light pulses (HILP) High-power pulsed light for microbial decontamination of some fruits treatments for the control of Escherichia coli and Listeria innocua in apple and vegetables with different surfaces. Journal of Food, Agriculture and juice, orange juice and milk. Food Microbiology 28: 14–20. Environment 10: 162–167. Paškevičiūtė, E., Lukšienė, Ž. (2009). High-power pulsed light for MacGregor, S. J., Rowan, N. J., Mcllvaney, L., Anderson, J. G., Fouracre, R. A., decontamination of chicken breast surface. Cheminė Technologija 4: 53. Farish, O. (1998). Light inactivation of food-related pathogenic bacteria Paskeviciute, E., Buchovec, I., Luksiene, Z. (2011). High-power pulsed using a pulsed power source. Letters in Applied Microbiology 27: 67–70. light for decontamination of chicken from food pathogens: A  study on Maftei, N. A., Ramos-Villarroel, A. Y., Nicolau, A. I., Martín-Belloso, O., antimicrobial efficiency and organoleptic properties. Journal of Food Soliva-Fortuny, R. (2014). Influence of processing parameters on the Safety 31: 61–68. pulsed-light inactivation of Penicillium expansum in apple juice. Food Pataro, G., Muñoz, A., Palgan, I., Noci, F., Ferrari, G., Lyng, J. G. (2011). Control 41: 27–31. Bacterial inactivation in fruit juices using a continuous flow pulsed light Manzocco, L., Da Pieve, S., Maifreni, M. (2011). Impact of UV-C light on (PL) system. Food Research International 44: 1642–1648. safety and quality of fresh-cut melon. Innovative Food Science and Pereira, R. N., Vicente, A. A. (2010). Environmental impact of novel thermal Emerging Technologies 12: 13–17. and non-thermal technologies in food processing. Food Research Manzocco, L., et al. (2014). Effect of pulsed light on safety and quality of fresh International 43: 1936–1943. egg pasta. Food and Bioprocess Technology 7: 1973–1980. Proulx, J., et  al. (2017). Short communication: Influence of pulsed light Miller, B. M., Sauer, A., Moraru, C. I. (2012). Inactivation of Escherichia coli treatment on the quality and sensory characteristics of cheddar cheese. in milk and concentrated milk using pulsed-light treatment. Journal of Journal of Dairy Science 100: 1004–1008. Dairy Science 95: 5597–5603. Rajkovic, A., Tomasevic, I., De Meulenaer, B., Devlieghere, F. (2017). The effect Misra, N. N., Tiwari, B. K., Raghavarao, K. S.  M. S., Cullen, P. J. (2011). of pulsed UV light on Escherichia coli O157: H7, Listeria monocytogenes, Nonthermal plasma inactivation of food-borne pathogens. Food Salmonella Typhimurium, Staphylococcus aureus and staphylococcal Engineering Reviews 3: 159–170. enterotoxin A on sliced fermented salami and its chemical quality. Food Moreaua, M., Nicorescua, I., Turpina, A. S., Agoulonb, A., Chevaliera, S., Control 73: 829–837. Orangea, N. (2011). Decontamination of spices by using a pulsed light Ramos-Villarroel, A. Y., Aron-Maftei, N., Martín-Belloso, O., Soliva-Fortuny, treatment. In: Food Process Engineering in a Changing World, Proceedings R. (2012). The role of pulsed light spectral distribution in the inactivation of the 11th International Congress of Engineering and Food (pp. 22–26). of Escherichia coli and Listeria innocua on fresh-cut mushrooms. Food Control 24: 206–213. Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 201 Ramos-Villarroel, A. Y., Martín-Belloso, O., Soliva-Fortuny, R. (2011). Bacterial Takeshita, K., et  al. (2003). Damage of yeast cells induced by pulsed light inactivation and quality changes in fresh-cut avocado treated with intense irradiation. International Journal of Food Microbiology 85: 151–158. light pulses. European Food Research and Technology 233: 395–402. Thirumdas, R., Sarangapani, C., Annapure, U. S. (2015). Cold plasma: A novel Ramos-Villarroel, A. Y., Martín-Belloso, O., Soliva-Fortuny, R. (2015). non-thermal technology for food processing. Food Biophysics 10: 1–11. Combined effects of malic acid dip and pulsed light treatments on the Tomašević, I. (2015). The effect of intense light pulses on the sensory inactivation of Listeria innocua and Escherichia coli on fresh-cut produce. quality and instrumental color of meat from different animal breeds. Food Control 52: 112–118. Biotechnology in Animal Husbandry 31: 273–281. Ramos-Villarroel, A., Aron-Maftei, N., Martín-Belloso, O., Soliva-Fortuny, R. Uesugi, A. R., Moraru, C. I. (2009). Reduction of listeria on ready-to-eat (2014). Bacterial inactivation and quality changes of fresh-cut avocados as sausages after exposure to a combination of pulsed light and nisin. Journal affected by intense light pulses of specific spectra. International Journal of of Food Protection 72: 347–353. Food Science and Technology 49: 128–136. US Food and Drug Administration. (2004). FDA Guidance to Industry, 2004: Rastogi, N. K. (2011). Opportunities and challenges in application of Recommendations to Processors of Apple Juice or Cider on the Use of ultrasound in food processing. Critical Reviews in Food Science and Ozone for Pathogen Reduction purposes. Nutrition 51: 705–722. Valdivia-Nájar, C. G., Martín-Belloso, O., Giner-Seguí, J., Soliva-Fortuny, R. Rowan, N. J., MacGregor, S. J., Anderson, J. G., Fouracre, R. A., McIlvaney, L., (2017). Modeling the inactivation of Listeria innocua and Escherichia Farish, O. (1999). Pulsed-light inactivation of food-related microorganisms. coli in fresh-cut tomato treated with pulsed light. Food and Bioprocess Applied and Environmental Microbiology 65: 1312–1315. Technology 10: 266–274. Salinas-Roca, B., Soliva-Fortuny, R., Welti-Chanes, J., Martín-Belloso, O. Wambura, P., Verghese, M. (2011). Effect of pulsed ultraviolet light on quality (2016). Combined effect of pulsed light, edible coating and malic acid of sliced ham. LWT-Food Science and Technology 44: 2173–2179. dipping to improve fresh-cut mango safety and quality. Food Control 66: Wang, C. Y., Huang, H. W., Hsu, C. P., Yang, B. B. (2016). Recent advances 190–197. in food processing using high hydrostatic pressure technology. Critical Sauer, A., Moraru, C. I. (2009). Inactivation of Escherichia coli ATCC 25922 Reviews in Food Science and Nutrition 56: 527–540. and Escherichia coil O157:H7 in apple juice and apple cider, using pulsed Xu, W., Wu, C. (2016). The impact of pulsed light on decontamination, quality, light treatment. Journal of Food Protection 72: 937–944. and bacterial attachment of fresh raspberries. Food Microbiology 57: Señorans, J., Ibáñez, E., Cifuentes, A. (2003). New trends in food processing. 135–143. Critical Reviews in Food Science and Nutrition 43: 507–526. Xu, W., Chen, H., Huang, Y., Wu, C. (2013). Decontamination of Escherichia coli Sharma, R. R., Demirci, A. (2003). Inactivation of Escherichia coli O157: O157:H7 on green onions using pulsed light (PL) and PL-surfactan-sanitizer H7 on inoculated alfalfa seeds with pulsed ultraviolet light and response combinations. International Journal of Food Microbiology 166: 102–108. surface modelling. Journal of Food Science 68: 1448–1453. Yi, J. Y., Bae, Y. K., Cheigh, C. I., Chung, M. S. (2017). Microbial inactivation Soliva-Fortuny, R., Balasa, A., Knorr, D., Martín-Belloso, O. (2009). Effects of and effects of interrelated factors of intense pulsed light (IPL) treatment for pulsed electric fields on bioactive compounds in foods: A review. Trends in Pseudomonas aeruginosa. LWT-Food Science and Technology 77: 52–59. Food Science and Technology 20: 544–556. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Food Quality and Safety Oxford University Press

Pulsed light processing of foods for microbial safety

Food Quality and Safety , Volume 1 (3) – Oct 13, 2017

Loading next page...
 
/lp/oxford-university-press/pulsed-light-processing-of-foods-for-microbial-safety-cSjO4k60NW

References (111)

Publisher
Oxford University Press
Copyright
© The Author 2017. Published by Oxford University Press on behalf of Zhejiang University Press.
ISSN
2399-1399
eISSN
2399-1402
DOI
10.1093/fqsafe/fyx017
Publisher site
See Article on Publisher Site

Abstract

The demand for processed foods and the awareness about food quality and safety are increasing rapidly. The consumers’ demand for minimally processed foods and growing competition in the market have made the processors to adopt newer non-thermal technologies that preserve nutrients and sensory properties of the products. Conventionally, heat processing of foods is carried out to convert raw material into value-added product, reduce or eliminate microbial load to improve safety, and extend shelf life. Some of the limitations of thermal processing techniques can be overcome by employing non-thermal processes. High hydrostatic pressure, pulsed electric field, ultrasound, cold plasma, dense phase carbon dioxide, ozone, and pulsed light (PL) processing are gaining popularity in food processing. PL technology is a non-thermal technology, where sterilization and decontamination are achieved by impinging high-intensity light pulses of short durations on surfaces of foods and high-transmission liquids. Although a few reports on the PL technology are available, in-depth studies on this are needed to adopt at a commercial level. The present review provides an overview of light-based processing of foods and covers important aspects such as different PL systems used for processing of foods, mode of action of PL on microbes, the effect of PL on liquid foods, surface decontamination of foods and parameters that affect PL efficacy, combination processing with PL. With the growing demand in non-thermal processing for the technological advancement in the area of generation of light, light-based processing will be a promising technology for microbial load reduction. Key words: Pulsed light; Food safety; Non-thermal processing; Minimally processed; Microbial load. of colours and vitamins (Devlieghere et al., 2004). High-temperature Introduction short-time processes, electromagnetic radiation-based microwave, As the human evolution progressed, the way food being consumed radio frequency heating, and ohmic heating techniques have gained and their priorities have also been evolved. The consumption of focus in the recent past as alternative and rapid heating techniques to processed foods is on the rise due to change in lifestyle, particularly minimize the severity of heat treatment and thereby enhance product in urban areas. Traditional thermal-based food-processing methods quality. such as appertization, pasteurization, and canning have been Over the past few years, consumer demand for fresh, natural, dependent on high temperature, to ensure prolonged shelf life and minimally processed foods with better quality has increased. and food safety. Although thermal processes are efficient tools To address this, researchers are working on developing alternative for microbial inactivation, they also contribute to undesirable techniques that not only meet the consumer demand but also energy- changes in food matrix such as structural alteration of proteins efficient, cost-effective, and rapid. Many novel technologies that and polysaccharides, production of free radicals, affecting the functionality of food and flavour, textural softening, and destruction do not involve heat processing have been developed to inactivate © The Author 2017. Published by Oxford University Press on behalf of Zhejiang University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 188 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 microorganisms. The novel non-thermal technologies such as high per the literature reports available, the three major commercial hydrostatic pressure (HHP), pulsed electric field (PEF), ultrasound companies producing disinfection systems based on PL are (US), cold plasma, dense phase carbon dioxide, ozone, and pulsed SteriBeam Systems from Germany, Xenon Corporation from USA, light (PL) processing are gaining popularity in food processing. and Claranor from France. Experiments conducted by Hierro et al. These technologies hold several promises by preserving the delicate (2011), Lasagabaster et al. (2011), Ramos-Villarroel et al. (2014), sensory and nutritional qualities of food and hence used for minimal Maftei et al. (2014), Koh et al. (2016a), Moreira et al. (2017), processing of food products (Ortega-Rivas and Salmerón-Ochoa, and Valdivia-Nájar et al. (2017) are associated with SteriBeam, 2014). These technologies offer several advantages compared to whereas results reported by Keklik et al. (2010), Wambura and thermal processing by minimizing the effect of heat on food and Verghese (2011), Pataro et al. (2011), Muñoz et al. (2011), Gómez minimization of flavour loss (Norton and Sun, 2008; Soliva-Fortuny et al. (2012a,b), Xu et al. (2013), and Huang and Chen (2014) et  al., 2009; Chawla et  al., 2011; Misra et  al., 2011; Rastogi, were obtained with a Xenon Corporation device, mainly the model 2011; Thirumdas et al., 2015; Wang et al., 2016). Among the non- SteriPulse™-XL 3000. Artíguez et al. (2011), Levy et al. (2012), thermal technologies, one of the emerging technologies is light- Nicorescu et al. (2013), Manzocco et al. (2014), Ignat et al. (2014), based processing. The present review deals with the usage of this Fernández et al. (2016), and Rajkovic et al. (2017) carried out the technology for microbial load reduction in foods. experiment with the PL system from Claranor with multiple xenon lamps. MacGregor et al. (1998) used a PL generator including rectangular PVC housing, pulse generator, and a control circuit PL Processing for bacterial inactivation. This bench-top experimental facility had two inoculated Petri dishes inclined at 45° received equivalent PL technology is a non-thermal technology, where decontamina- doses. Takeshita et al. (2003) studied the damage caused by PL tion of foods such as fruit juices, meat products, vegetables, and on Saccharomyces cerevisiae using the system similar to that fruits is achieved by using high-intensity light pulses for a short designed by Dunn et al. (1995) having power supply unit and a duration of time. The PL includes a wide wavelength range of 200– flash lamp that produce PL consisting of intense flashes of broad- 1100 nm, which includes ultraviolet (UV): 200–400 nm, visible spectrum white light (200–1000 nm). Fine and Gervais (2004) used (VIS): 400–700 nm, and near-infrared region (IR): 700–1100 nm One-Shot EN2/2143-1 unit, a 3-fluidized bed as a PUV system (Elmnasser et al., 2007; Palgan et al., 2011). The term pulsed light is having adjustable air nozzles and compressed air that allows known since 1980 and was first adopted by the US Food and Drug tangential blowing for fluidization of the food powders; flash lamp Administration (FDA) for food processing in 1996 (FDA, 1996). surrounded by a quartz jacket with water circulation to limit lamp To increase the safety of fruit and vegetable juices, US FDA regula- overheating and a reflecting cylinder. Paskeviciute et al. (2011) and tion has implemented 5-log pathogen reduction process (US FDA, Luksiene et al. (2012) constructed high-power PL device in their 2004). Significant microbial reduction in very short treatment time, laboratory having a chamber, a reflector with a flash lamp, and a low environmental impact, and its high flexibility are some of the power supply for chicken, vegetable, and fruits decontamination, major benefits of PL (Uesugi and Moraru, 2009; Oms-Oliu et  al., respectively. Sharma and Demirci (2003) and Ozer and Demirci 2010b). Xenon flash lamps are more environment-friendly than (2006) conducted the experiment to decontaminate the alfalfa continuous-wave UV lamps as they do not use mercury (Gomez- seeds and fish fillets, respectively, using a PL sterilization chamber Lopez et al., 2007). One of the big advantages of PL over static UV containing treatment chamber, UV strobe, tray, and a control treatment is the fact that the energy is delivered in a very short time module. Similarly, Bialka and Demirci (2007) used a laboratory (Sauer and Moraru, 2009; Chaine et al., 2012). PL systems have scale, batch PL system for decontamination of blueberries with relatively low operation costs and generate only reduced amounts slight modification in the set-up having a quartz window and a of solids wastes (Pereira and Vicente, 2010). The benefits include cooling blower. PUV treatment was carried out in the continuous reduced risk from foodborne pathogens on public health, extended flow-through system for inactivating Staphylococcus aureus in the shelf life of the product, and improved economics during food milk. The system included a UV chamber, UV lamp, pump with distribution (Ozer and Demirci, 2006). PL has potential applica- variable flow rate, and V-groove reflector (Krishnamurthy et al., tions in food processing that requires a rapid disinfection where 2007). surface contamination is a concern for microbial contamination Choi et  al. (2010) designed a laboratory-scale PL system for such as fresh whole fruit and vegetable commodities, hard cheeses non-thermal sterilization of infant foods. They used water bath as or meat slices, and so on. Even though the PL processing is consid- a cooling device to dissipate the heat generated during the discharge ered as ‘non-thermal’, it has the limitation of sample heating due by quartz lamp and oscilloscope to view the exponential decay pulse. to longer treatment time, which may cause thermal inactivation of Cheigh et al. (2013) designed a laboratory-scale PL system consisting microbes. Significant temperature increase caused due to longer PL a xenon lamp used to produce intense pulsed light (IPL) with an treatments has an extra effect on microbial reductions depending emission spectrum in the range of 200–1100  nm for inactivating on the matrix properties (Bialka and Demirci, 2008; Huang and Listeria  monocytogenes on solid medium and seafoods (Figure  1). Chen, 2014). Hwang et  al. (2015) designed an ILP treatment unit for microbial inactivation of various liquid samples, which had a pulse generator PL Treatment Systems for Microbial Load and a spectroradiometer to determine the irradiance of xenon Reduction lamp, cooling system (fans) on either sides of the lamp to dissipate The pioneer company producing PL equipment for application the generated heat. Similarly, Yi et  al. (2017) also self-designed a in water purification systems and virus inactivation systems for laboratory-scale IPL for describing the IPL inactivation curves of biopharmaceutical manufacturers is Purepulse Technologies Inc. Pseudomonas  aeruginosa under different pulse conditions. Hwang (San Diego, California), a subsidiary of Xenon Corp., which et  al. (2017) constructed a pilot-scale IPL device by upgrading commercialized the PureBright™ system (Dunn et al., 1995). As the xenon lamp and power supply. Sesame seeds inoculated with Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 189 bacteria, moulds, and yeast were treated using this PL system. Pataro power also contribute to the destructive effect on microorganisms et  al. (2011) carried out microbial-inactivation experiments using (Elmnasser et al., 2007). The antimicrobial properties of UV light a laboratory-scale continuous-flow PL apparatus which consisted on bacteria are attributed to absorption of radiation by conjugated of a linear Xenon flash lamp, power/control module, sterilization carbon–carbon double bonds in nucleic acids and proteins, and chamber, photoelectric detector module, and cooling system subsequent DNA structural changes (Ramos-Villarroel et al., 2012). (Figure 2). Ferrario and Guerrero (2016) performed PL treatment in Cheigh et al. (2013) identified the cell damage on the foodborne apple juice with the help of a continuous flow-through PL system. pathogen, L. monocytogenes treated with UV-C and IPL with the Caminiti et al. (2011b), Muñoz et al. (2012), and Chaine et al. (2012) help of transmission electron microscopy (TEM). UV-C–treated L. also used a continuous flow-through PL system for processing liquids monocytogenes cells were similar in structure to that of untreated like fruit juices and sugar syrup. cells except for a blurry and indistinct cell wall (Figure 3). In contrast, IPL-treated cells showed the destruction of cell wall structures, cytoplasm shrinkage, and rupture of the internal organization leading Mode of Action of PL on Microbes to leakage of cytoplasmic content and ultimately to cell death (Cheigh UV was the only agent responsible for the inactivation of pathogens et al., 2012). But, conversely, Krishnamurthy et al. (2010) concluded and no antibacterial effect attributed to IR or VIS light was found that S. aureus treated with PUV had cell wall damage, disintegration, (Paškevičiūtė and Lukšienė, 2009; Ramos-Villarroel et al., 2014; cellular content leakage, cytoplasmic membrane shrinkage, and also Kramer et al., 2015). In addition, it has been shown that both found that internal cellular structures were collapsing. Cheigh et al. the VIS and IR regions of PL in combination with its high peak (2012) also indicated that the IPL treatment was effective in reducing the bacterial population in L. monocytogenes and Escherichia coli O157:H7 than continuous UV-C irradiation. However, despite a high energy density and broad spectrum (with wavelengths including the UV-C region), IPL treatment exerted milder photochemical effects on the cells (e.g. the formation of double-strand breaks) than did UV-C irradiation. Levy et al. (2012) mentioned that PL had a better effect than continuous UV treatment for Aspergillus niger spores. Similarly, Orlowska et al. (2013) also found 5-log reduction of E. coli in water at 10 mJ/cm for continuous mercury lamps and at 5 mJ/cm for pulsed lamps. Nicorescu et al. (2013) studied the effect of PL on the structural differences in Bacillus subtilis inoculated on powdered spices with the help of scanning electron microscopy (SEM). The cell membrane was disrupted clearly forming deep craters in the cell wall after PL treatment, whereas it was contrary in the case of B. subtilis treated in suspension (Figure 4). The cell wall disruption may be due to photothermal stress and germicidal action caused by the PL having a UV component. It altered the DNA structure by decreasing supercoiling of DNA and then breaking into a single strand that in turn leads to cell death (Nicorescu et al., 2013). Xu and Wu (2016) studied the structural difference in E. coli treated with PL and confirmed that the structural changes in membrane integrity of E. coli, leading to flattening of cells, can be due Figure 1. Schematic diagram of the intense pulsed light (IPL) system (Cheigh to heating of intracellular fluid, and UV light absorption by bacteria et al. 2013). Figure 2. Schematic diagram of the continuous flow PL system (Pataro et al., 2011). 190 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 health status. Inactivation of these pathogens on liquid food complexes are mentioned in Table 1. PL processing is influenced by various factors that dictate its efficiency on microbial inactivation, retention of quality, and other properties of the product. Important factors that determine the effectiveness of PL is the fluence level applied on the sample, the amount of energy (dose or number of pulses) and wavelength of light/composition of the spectrum (Ramos-Villarroel et al., 2012). Inactivation of microbes is higher for PL treatment with higher pulse number and higher intensity (MacGregor et al., 1998; Maftei et al., 2014; Ramos-Villarroel et al., 2014). It is indicated that when the spectral range of the PL treatments, particularly the UV component, is altered by using filters, the inactivation of E. coli and Listeria innocua is lower (Ramos-Villarroel et al., 2012). And among the sub-divisions of UV, UV-C–containing spectrum was more effective in inactivating B. subtilis and A. niger spores (Levy et al., 2012). Absorption of light, particularly in the UV region, and shielding of microbes by suspended matter are significant limiting factors in PL treatment of microbes in liquid substrates (Sauer and Moraru, 2009). PL has very limited penetration depth in opaque media and is capable of targeting the surface microorganisms. Penicillium expansum inactivation efficiency of PL treatment dramatically decreased from 3.21 to 1.58 log colony forming units (CFU)/ml when the depth of apple juice was increased from 6 to 10 mm (Maftei et al., 2014). Inactivating effect of PL treatments against P. expansum was greatly depended on the microbial load that is 1.30 and 3.2 log reduction 5 4 for 3 × 10 and 2.3 × 10 CFU/ml, respectively, for inoculated juice samples (Maftei et al., 2014). The susceptibility trend is reported to be Gram-negative bacteria > Gram-positive bacteria > bacterial spores > fungal spores (Rowan et al., 1999; Anderson et al., 2000; Levy et al., 2012). S. cerevisiae was found to be the most resistant strain to PL treatment than L. innocua, E. coli, and Salmonella enteritidis in PL-treated apple juice system (Ferrario et al., 2015b). In contrast, Nicorescu et al. (2013) have reported that bacteria is more resistant than yeast for PL treatment, whereas viruses are more resistant to PL treatment compared to bacteria (Huang et al., 2017). Gram-negative bacteria, E. coli, is more susceptible to PL when compared to Gram- positive bacteria, L. innocua, which may be due to the presence of distinguishing structural/compositional variation in the cell walls of these bacteria (MacGregor et al., 1998; Otaki et al., 2003; Ramos- Villarroel et al., 2011; Ramos-Villarroel et al., 2012). E. coli is more sensitive to UV-C treatment than L. monocytogenes as the Weibull model parameters also confirms, which is a better fit compared to Figure  3. TEM of L.  monocytogenes: (A) untreated, (B) treated with 150 the linear model for evaluation the microbial inactivation (Bialka pulses (30 s), (C) treated with 900 pulses (180 s) with IPL at a fluence of 1.75 and Demirci, 2008; Bialka et al., 2008; Chun et al., 2010). Bacillus mJ/cm per pulse, and (D) treated for 1000  s with UV-C at 254  nm (Cheigh is more susceptible than mesophilic bacteria, and L. innocua is more et al., 2013). resistant than Pseudomonas fluorescens to PL at low temperature and low fluence levels (Luksiene et al., 2012; Hilton et al., 2017). Hilton can be attributed to overheating, intercellular water vapourization, et al. (2017) indicated that PL treatment effectiveness is independent and subsequent membrane disruption. PL processing is a multi- of temperature for E. coli and P. fluorescens in clear liquid substrates target process in which both photothermal/photophysical and within the temperature range of 5–40°C. However, in the case photochemical effects are caused, thus alteration in cell membrane of L. innocua, the effect of temperature and PL was observed at disruption/leakage of cell content and chromosomal DNA damage 50°C. Higher PL resistance shown by Listeria spp. compared to occurs, respectively (Cheigh et al., 2012; Ramos-Villarroel et al., Pseudomonas phosphoreum and Serratia liqueficans could be 2012; Nicorescu et al., 2013). related to the presence of photoreactive substances and protective compounds that contribute to the antimicrobial effectiveness of PL (Lasagabaster and De Maranon, 2012). Ramos-Villarroel et al. Effect of PL on Liquid Foods (2011) mentioned that IPL sensitivity by microorganisms may be PL processing is being applied on various liquid products for related to differences in bacterial cell wall composition due to their decontaminating the foodborne pathogens that affect the human protective and repair mechanisms against the damage. PL induced Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 191 Figure  4. (i) SEM of B.  subtilis vegetative cells in suspension: (a) untreated samples; (b) treated by PL at 0.6 J/cm /flash. (ii) SEM of ground black pepper artificially inoculated with B. subtilis vegetative cells: (a) untreated samples; (b) treated by PL at 1 J/cm /flash (Nicorescu et al., 2013). Table 1. The effect of PL treatment on microbial inactivation in liquid foods. Food product Microorganism Treatment Log reduction Reference Milk S. aureus 3 pulses/s and 1.27 J/cm /pulse; distance from the UV 0.55–7.23 log CFU/ Krishnamurthy et al. light strobe 5–11 cm; flow rate 20–40 ml/min ml (2007) Apple juice E. coli ATCC 25922 Frequency 3 pulses/s and pulse width 360 µs: 2.66 log CFU/ml Sauer and Moraru E. coli O157: H7 fluence 12.6 J/cm 2.52 log CFU/ml (2009) Apple cider E. coli ATCC 25922 2.32 log CFU/ml E. coli O157:H7 3.22 log CFU/ml Apple juice E. coli 3 pulses/s (pulse width 360 µs) of 100–1100 nm width, 4 log CFU/ml Pataro et al. (2011) 2 2 L. innocua approximately, 1.21 J/cm /pulse: PL fluence of 4 J/cm 2.98 log CFU/ml Orange juice E. coli 2.9 log CFU/ml L. innocua 0.93 log CFU/ml E. coli Fluence of 6 J/cm 2.02 log CFU/g L. innocua 1.77 log CFU/g Sugar syrup B. subtilis spores Pulses (250 µs): fluence 1.5 J/cm 4.2 log CFU/ml Chaine et al. (2012) S. cerevisiae Fluence 1.23 J/cm 5.4 log CFU/ml G. stearothermophilus spores Fluence 1.86 J/cm >4 log CFU/ml A. acidoterrestris spores 3 log CFU/ml A. niger Fluence 1.2 J/cm 1.3 log CFU/ml Infant food L. monocytogenes Width 1.5 µs; operating time 0–600 s; 2300 µs 1 log CFU/g Choi et al. (2010) treatment 4700 µs of treatment 2 log CFU/g 9500 µs of treatment 3 log CFU/g Milk E. coli 200–1100 nm, 3 Hz and 360 µs, 1.17 J/cm /pulse at a 0.61–1.06 log CFU/ Palgan et al. (2011) distance of 2.5 cm: 7–28 J/cm ml L. innocua 0.51–0.84 log CFU/ ml S. Thyphimurium 0.51–1.73 log CFU/ cm sublethal injury of S. cerevisiae cells at low doses up to 12 J/cm In contrast, PL did not cause any sublethal damage to the bacterial (Ferrario et al., 2014). PL treatment causes sublethal damages which cells such as E. coli, L. monocytogenes, S. Typhimurium, and V. make cells more sensitive to stress in subsequent stages such as parahaemolyticus (Hierro et al., 2012). Listeria and Salmonella were storage at low temperature (Lasagabaster and de Marañón, 2014). not found to have the ability to repair the cell damage induced by 192 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 PL through photoreactivation mechanism (Paskeviciute et al., 2011). Hence, foods with high carbohydrates but poor in fats and proteins, Sublethal damage of bacteria cells by PL treatment confirmed that such as fruits and vegetables, seem to be more appropriate for IPL membrane damage is one of the important causes for bacterial processing (Gómez-Lopez et al., 2005). inactivation, apart from microbial DNA damage, depending on the Continuous flow-through PL of apple juice was more effective energy dose and sensitivity of light pulses (Pataro et al., 2011). in inactivating microbes than batch mode PL (Muñoz et  al., 2012; Additionally, distance of the sample from the light source, treat- Ferrario et  al., 2013; Ferrario and Guerrero, 2016). Chaine et  al. ment time, volume of the sample, geometry of the treatment cham- (2012) mentioned that PL requires shorter residence time for micro- ber, orientation, and design of lamps are also the critical factors that bial inactivation and subsequently higher flows of liquid foods could are to be optimized in order to accomplish maximum effectiveness of be treated using various parallel modules of PL treatment. In apple the PL treatment (Gomez-Lopez et al., 2007; Krishnamurthy et al., juice, a maximum reduction of 7.29 log CFU/ml was achieved for 2007; Ignat et al., 2014; Xu and Wu, 2016). Inactivation effects of E. coli with high turbulence (3000 rpm) compared to 4.46 and 2.66 IPL treatment on L. monocytogenes showed significant inactivation log CFU/ml for the treatment with low turbulence (500  rpm) and compared to UV-C treatment due to higher penetration depth and static treatment, respectively. For the same high turbulence treat- emission power of IPL (Cheigh et al., 2013). Food parameters that ment, inactivation levels of E.  coli in apple cider of up to 5.49 log influence PL effectiveness for microbial inactivation are reflection CFU/ml greater than low turbulence and about 3.2 log CFU/ml coefficient, intrinsic transparency and surface condition of the item, higher than static treatment was observed by Sauer and Moraru thickness, colour, viscosity, moisture content, turbidity, light trans- (2009). The use of turbulence enhanced the inactivation of E. coli in missivity, the presence of particulate material, and flow conditions reconstituted milk by PL treatment (Miller et  al., 2012). Thus, tur- of the product (Choi et al., 2010; Artíguez et al., 2011; Ferrario and bulence can significantly enhance the effectiveness of PL treatment, Guerrero, 2016). Indeed, physiochemical factors such as chemical presumably by maximizing exposure of microbial cells to the inci- composition, total soluble compounds, pH and light absorbance dent light and could also disintegrate the clusters/clumps of micro- (especially due to compounds as carotenoids) could potentially pro- bial cells that lead to increasing microbial inactivation. tect the microorganisms from the PL treatments, and thus differ- A high fluence of 26.25 J/cm resulted in 3.2 log reduction in ent microbial inactivation levels are achieved (Valdivia-Nájar et al., the total microbial count, and concomitantly, milk temperature 2017). As the total solids in reconstituted milk increased, reduction was increased to 55°C, which indicated a combined effect of pho- levels of E. coli decreased by 2.0, 0.62, and 0.45 log CFU for 9.8%, tochemical and photothermal damage of natural microflora by PL 25%, and 45% total solids, respectively. The effect of optical prop- in raw milk (Innocente et al., 2014). E. coli and L. innocua counts erties of beverages on P.  aeruginosa inactivation by IPL has been were decreased by ≥4.7 and 1.93 log CFU/ml in apple juice treated reported (Miller et al., 2012; Hwang et al., 2015). They found that with PL at 28 J/cm , and subsequent recovery of the cell was not beverages with higher transparency like apple juice, carbonated drink, observed even after 48 h (Palgan et al., 2011). Similarly, exposure of 2 2 and plum juice showed 7 log reductions with 12.17–24.35 J/cm , 17.5 kJ/m fluence, PL found to decrease L.  brevis population in whereas grape juice, milk, and coffee showed a lower reduction apple juice by 3 log cycle (Ignat et al., 2014). PL did not affect pH, value of 1–1.9 log CFU/ml with a fluence of 29.21 J/cm . Similarly, Brix, and non-enzymatic browning index, whereas it did slightly due to differences in transparency of the medium (1 mm thickness), affect the colour of apple juice (Muñoz et  al., 2012). Similarly, no lower inactivation levels of E. coli and L. innocua were also reported change in colour, soluble substances, and pH of the product was by Palgan et  al. (2011) in milk (1275.2) and orange juice (79.7) reported until 53.3 J/g PL treatment in apple juice (Maftei et al., when compared to apple juice (5.81) and maximum recovery diluent 2014). The results of the sensory studies conducted by Palgan et al. (0.74) with lower ɛ. (2011) on reconstituted apple juice exposed to PL at 28 J/cm flu- PL was more efficient in the apple juice system with lower tur - ence showed that there was no significant difference in terms of col- bidity compared to orange and strawberry juices suggesting that our, sweetness, odour, or acidity of apple juice, but lowest score was higher turbidity of juices diminishes the PL efficiency (Ferrario observed for flavour compared to either control or samples treated et  al., 2015a). Chaine et  al. (2012) also observed lower inactiva- with PL for a shorter time. tion of B.  subtilis spores in sugar syrup (3 log reduction than in distilled water—4.6 log reduction) after exposure to 1.8 J/cm , PL Effect of PL for Surface Decontamination under static conditions. They suggested that these differences in the of Foods light transmission in the UV-C region as the absorption coefficient of clear syrup at 254 nm resulted in 200-fold higher than that cor- Various solid food products are being decontaminated by PL responding to distilled water. Ferrario et  al. (2013) concluded that processing for producing safe food, which increases the shelf life PL effectiveness is negatively influenced by the higher absorbance of the products. Few of the examples are listed in Table 2. Log values of liquids in the UV-C region. Properties of food surface have reduction values of E. coli and L. innocua reported by Ramos- an impact on decontamination efficiency (Kramer et al., 2017). Choi Villarroel et al. (2014) showed that fresh-cut avocado treated at et al. (2010) found that inactivation of L. monocytogenes at 15 kV 305–1100 nm (2.74 and 1.35 log CFU/g, respectively) were higher in infant meal (dark-coloured viscous product with 14% carbohy- than those of samples treated at 400 to 1100 nm (0.83 and 0.68 drates and 85.98% water) was effective (3 log reduction at 4800 µs) log CFU/g, respectively), indicating the antibacterial effect of but lower than light-coloured, thin, infant beverage (5 log reduction UV component. Efficacy of PL treatment depends on the type of at 3500 µs) which is due to the product characteristics. PL treatment microbe, inoculum size, and inoculation site (Huang and Chen, efficiency was hindered by the presence of milk fat due to scattering 2014). Manzocco et al. (2014) studied the effect of inoculation site of light by fat globules (Miller et al., 2012). Increasing levels of oil by inoculating Salmonella enterica in the pasta dough before rolling and protein reduced the killing efficiency of IPL since proteins have into sheet and after sheeting. They observed that log reduction was high absorption at about 288 nm and above of the UV region, lipids lower in the case of S. enterica inoculated in the dough before also absorb UV, decreasing the effective radiation dose on microbes. sheeting (0.8 log reduction) when compared to that of inoculated Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 193 Table 2. The effect of PL treatment on surface decontamination of foods. Food product Microorganism Treatment Log reduction Reference Fresh-cut melon Enterobacteriaceae UV-C irradiance on melon cubes was 2.61 log CFU/g Manzocco et al. (2011) 2 2 20 W/m up to 10 min: fluence—1200 J/m Fluence—6000 J/m 2.32 log CFU/g Fluence—12 000 J/m 2.14 log CFU/g Fresh-cut E. coli Full spectrum (λ = 180–1100 nm): total 3.03 log CFU/g Ramos-Villarroel et al. mushrooms L. innocua fluence of 12 J/cm 2.66 log CFU/g (2012) E. coli Fluence of 6 J/cm 2.02 log CFU/g L. innocua 1.77 log CFU/g Plum B. cereus Illumination spectrum was broad (200– 1.4 log CFU/g Luksiene et al. (2012) Tomato 1000 nm) and had maximal emission at 1.5 log CFU/g Cauliflower 260 nm; duration of light pulse was 112 µs, 1.3 log CFU/g Sweet pepper frequency 5 Hz: UV light dose 5.4 J/cm 1.8 log CFU/g Strawberry 1.5 log CFU/g Ground caraway B. subtilis 200 to 1100 nm with pulse duration of 0.8 log CFU/ml Nicorescu et al. (2013) 2 2 Ground black pepper 300 µs: treatment of 10 J/cm (1 J/cm × 10 Ground red pepper flashes) 1 log CFU/ml Blueberries E. coli O157:H7 Wavelength of 180–1100 nm with pulse 3.8->6.7 log CFU/g Huang and Chen Salmonella rate of 3 pulses/s and pulse width of 360 µs 4.8–5.7 log CFU/g (2014) for 5–60 s: PL fluence of 5–56.1 J/cm Spinach L. innocua 180 to 1100 nm with 17% of UV light. dura- 1.85 log CFU/g Agüero et al. (2016) E. coli tion—0.3 µs and fluence—8 J/cm 1.72 log CFU/g Egg shells S. enterica subsp. 200 to 1100 nm, with 20% of UV-C, 8% in 5 log CFU/egg shell Lasagabaster et al. enterica serovar Typhimurium UV-B and 12% in UV-A: treatments fluence (2011) of 2.1 J/cm Beef carpaccio E. coli Duration of the pulse is 250 µs, 30% UV 0.6–1.2 log CFU/ Hierro et al. (2012) light, 30% infrared radiation and 40% vis- cm S. Typhimurium ible light: fluencies of 0.7–11.9 J/cm 0.3–1.0 log CFU/ cm L. monocytogenes 0.3–0.9 log CFU/ cm Tuna carpaccio V. parahaemolyticus 0.2–1.0 log CFU/ cm L. monocytogenes 0.2–0.7 log CFU/ cm Fish products P. phosphoreum High-intensity pulses of 325 µs duration 5 log CFU/cm Lasagabaster and De S. liquefaciens and wavelengths from 200 to 1100 nm, 3.9 log CFU/cm Marañón (2012) S. putrefaciens with about 20% of UV-C, 8% of UV-B, and 2.1 log CFU/cm B. thermosphacta 12% of UV-A region: one pulse fluence of <1 log CFU/cm Pseudomonas 0.053 J/cm L. innocua RTE meat products L. monocytogenes Pulse is delivered in 250 µs that correspond 1.01–1.61 log CFU/ Ganan et al. (2013) 2 2 dry-cured loin to a fluence of 0.7 J/cm : total fluence ap- cm S. Thyphimurium plied 0.7–11.9 J/cm 0.51–1.73 log CFU/ cm Salchichon L. monocytogenes 0.89–1.81 log CFU/ cm S. Thyphimurium 0.26–1.48 log CFU/ cm Shrimp fillets L. monocytogenes 1.75 mJ/cm /pulse; pulse duration-1.5 µs; 2.2–2.4 log CFU/g Cheigh et al., (2013) Salmon fillets frequency-5 Hz; fluence—6.3 to 12.1 J/cm 1.9–2.1 log CFU/g Flatfish fillets 1.7–1.9 log CFU/g on the surface of egg pasta after sheeting (2.5 log reduction). Dip- on the chicken surface (Paskeviciute et al., 2011). Contrarily, Chun inoculated produce was harder to be decontaminated than spot- et al. (2009) reported that at 8000 J/m dose of UV-C irradiation, inoculated ones due to infiltration of E. coli into the open surface 2.74 log reduction was achieved in L. monocytogenes on RTE ham, structures of the produce (Xu et al., 2013). In contrary, at 8000 J/ whereas it was only 2.02 and 1.72 log cycle for S. Typhimurium m dose of UV-C irradiation, 2.16 log reduction was achieved in E. and Campylobacter jejuni, respectively. Whereas, one log reduction coli on ready-to-eat (RTE) salad surface, where it was 2.57 log cycle of E. coli and L. monocytogenes was achieved at the 60-s treatment for L. monocytogenes (Chun et al., 2010). PL treatment did not of UV light at 8-cm distance in raw salmon fillets (Ozer and show any significant difference in susceptibility of pathogen and Demirci, 2006). Paškevičiūtė and Lukšienė (2009) concluded that mesophiles. At 5.4 J/cm fluence of UV light, reduction by 2 and 2.4 the reduction of bacterial viability on the surface of chicken was a log CFU/ml was observed for Listeria and Salmonella, respectively, function of the light dose when the distance from the light source, 194 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 impulse repetition rate, and the voltage were constant. Only 0.99 preserving the quality of fruits by reducing sample heating, uniform log reduction of P. aeruginosa was observed on sesame seeds when PL exposure, and physical removal of bacterial cells due to the IPL treatment was applied, whereas 7 log reduction was observed agitation of the water. Colour discolouration was coupled with in P. aeruginosa inoculated mineral water. This large difference sample heating when blueberries treated with dry PL at 30 and 60 s in reduction is mainly due to the matrix type: while all sides of (Huang and Chen, 2014). Thus, wet PL can be considered as one sesame seeds could not be exposed to IPL because of shadowing of the potential non-chemical alternatives to chlorine washing with effect. The irregular surface of sesame seeds protected the hidden higher efficacy and environmentally friendly process. To promote microorganisms from IPL so that microbial reduction would not the quality of vegetables, and also to avoid shadowing effect of increase regardless of the fluence applied (Hwang et al., 2017). PL, wet PL treatment was carried out by Xu et al. (2013) for fresh Likewise, Moreaua et al. (2011) noticed the reduced effectiveness produce like green onions. Wet PL treatment showed time-dependent of PL in the case of peppercorn decontamination with B. subtilis log reduction for spot-inoculated green onions. However, wet PL compared to that of decontamination on glass marbles that could treatment had no effect on time for dip-inoculated produce (<1.2 be attributed to the non-uniform surface of the spice, which caused log reduction). At 30- and 60-s dry PL treatment on green onions, an insufficient microbial reduction. The surface topology plays a quality in terms of softer and shrunken tissue, colour, and smell were major role in PL treatment, as microbes can lodge on irregular altered. Dry PL at 5 s was more effective than 60-s wet PL treatment surfaces and thus reducing that effect of PL in the target organism (>4 log reduction) for E. coli inactivation in green onions (Xu et al., (Sauer and Moraru, 2009). PL treated at 5.4 J/cm for raspberry 2013). Egg decontamination efficacy by PL could also depend on and strawberry inactivated E. coli by 3.0 and 2.3 log CFU/g and washing process before PL processing (Hierro et al., 2009). Higher Salmonella by 3.4 and 3.9 log CFU/g, respectively. Variation in the Salmonella decontamination was obtained in unwashed egg shells reduction of microbes on the surface of raspberry and strawberry than washed ones which can be due to damage of egg cuticle that in can be attributed to shadowing/shielding effect (Bialka and Demirci, turn provide a protective shielding against PL. Washing procedures 2008). Due to shadowing/shielding effect, microbes on rough (washing with soap and warm water followed by immersion in surface structures have the chance of being protected by PL, thus by 70% ethanol and posterior eggshell flaming) could cause damage hiding in the sub-surface structures (Nicorescu et al., 2013; Maftei to the cuticle and thus facilitate cell penetration into pores and et al., 2014). Salmonella and E. coli showed a higher reduction in therefore protect bacteria being affected by light. Hierro et al. (2009) blueberry (4.2 and 5.7 log reduction, respectively) compared to that mentioned that there was a 2.49 log reduction of S. enteritidis in on strawberry (2.1 and 1.9 log reduction, respectively) at 22.5 J/cm unwashed egg shells. In contrast, a 5 log reduction in Salmonella due to the different topographical surface of the berries. The pres- counts were observed in both washed and unwashed eggshells ence of achenes on strawberry could potentially shadow microor- treated at 2.1 J/cm fluence. Lasagabaster et al. (2011) used different ganisms from highly directional coherent PL beam from reaching washing procedure for eggshells (immersion in 70% ethanol) and its target leading to partial decontamination compared to the even concluded that washing had no effect on PL antimicrobial smooth skin of blueberries (Huang et al., 2017). Cauliflower being effectiveness on the surface of eggshells and even did not detect any the most irregular surfaced vegetable was less decontaminated by Salmonella penetration into egg content. Salmonella inoculated on PL than other fruits and vegetables, which is said to be due to the eggshell was found to have photoreactivation mechanism, and hence shielding effect of PL and thus the antimicrobial efficiency of PL Hierro et al. (2009) advised to store eggs that are PL treated away exhibited clear dependence on surface irregularity (Luksiene et al., from light. 2012). Koh et al. (2016a) studied the effect of cut type on fresh- Inactivation efficacy of PL was similar for both total bacterial cut cantaloupe treated with PL. They found that sphere samples count (TBC) and total yeast and mould count (TYMC) as reported had significantly lesser microbial count compared to cuboid and by Xu and Wu (2016). Whereas at the end of the 10-day storage, triangular prism-shaped sample, which is due to area/volume ratio TBC and TYMC counts were significantly higher in PL 30  s than of the sample. Higher the area/volume ratio causes more wounds those in PL 5 s and PL 15 s, however, which was considerably lower on the product, thus higher electrolyte leakage leading to increased than control. This greater number of microbes on PL 30 s may be microbial growth. A higher percentage of microbial inactivation because of structural damage of raspberry (softer texture) due to of 50% was observed for sphere-shaped samples compared to the longer PL treatment that benefits microbial growth and a surface cuboidal or triangular prism, which could also be due to decreased structure that affected the attachment of bacterial cells by protecting scattering light around the edges of the sphere and lower shielding the pathogenic bacteria (Xu and Wu, 2016). The use of PL had effect due to lower initial microbial load (Koh et al., 2016a). reduced the amount of inoculated yeast cells on carrot slices by Sample temperature was found to increase with an increase in about three to four cycles (Kaack and Lyager, 2007), whereas it was pulses number, treatment time, and sample distance from the lamp 1.6 log cycles in apple discs exposed to PL (Gómez et  al., 2012b), (Wambura and Verghese, 2011; Ferrario et  al., 2013). Wambura due to shielding of microorganisms by rough apple surface and and Verghese (2011) observed 6°C temperature increase for every internalization into apple tissue that could have a major influence on 10-s PUV treatment. Similarly, Ferrario et  al. (2013) also found the inactivation pattern (Moreira et  al., 2017). Similarly, reduction that temperature of fruit juice treated for 60  s with PL increased in the native microflora was lower than L.  innocua and E.  coli between 7.4 and 16.8°C. To dissipate the temperature changes inoculated on spinach when treated with PL due to internalization due to sample heating, incorporation of the cooling systems in of endogenous microorganisms. And the initial load of microflora the equipment, external water-ethylene glycol cooling system was also significantly reduced, showing high efficiency for coliforms can be adopted that limits the heating rate and final temperature and its development was limited during refrigerated storage (Agüero of the product (Pataro et  al., 2011). Huang and Chen (2014) and et al., 2016). PL processing showed its capability to decontaminate Huang et  al. (2015) approached to overcome this limitation of PL and promote higher microbial stability during storage, thus by using wet PL treatment that is submerging the raspberries and increasing shelf life of the product (Ignat et  al., 2014). During the blueberries in agitated water. This process provided the benefits of cold storage, the counts of L.  innocua on fresh-cut tomatoes that Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 195 were subjected to PL treatments did not significantly change through of treated chicken depend on the process parameters and showed first 12 days of storage, whereas the gradual increase of L. innocua UV dose of 5.1 J/cm at 38°C had no changes on raw meat flavour counts on the untreated tomato slices were observed just after 4 days and taste. PUV light treatment affected the tissue structure of ham (Valdivia-Nájar et  al., 2017). Application of PL led to significantly which could be due to the destruction of the network and changes lower mesophilic aerobic count during the 14-day storage period in myofibrillar proteins (Wambura and Verghese, 2011). Sensory compared to untreated apple (Moreira et  al., 2017). PL treatment evaluation of PL-treated ham showed that there was no alteration could inactivate microbial growth and hence, extended the shelf life in colour, flavour, appearance, and odour, whereas, for bologna, of treated samples by 8  days, as compared to untreated fresh-cut differences for odour and flavour were observed at higher fluences cantaloupe (Koh et al., 2016a). Vacuum-packaged and -unpackaged than 4.2 J/cm (Hierro et al., 2011). Similarly, Tomašević (2015) also chicken frankfurters did not have any effect on log reduction found that there was no alteration in appearance and total score of L.  monocytogenes (maximum of 1.9 log CFU/cm ) with UV values of beef samples treated with IPL. In contrary, Hierro et al. treatment for 60  s at 5  cm; however, it caused colour and quality (2012) conducted the sensory analysis and found that PL fluences of changes in the samples (Keklik et  al., 2009). Decontamination of 8.4 and 4.2 J/cm or lower did not affect the raw attributes such as L.  monocytogenes in vacuum-packaged ham (1.78 log CFU/ cm ) odour and colour of beef, and tuna carpaccio, respectively. However, 2 2 was higher than bologna (1.11 log CFU/ cm ) at 8.4 J/cm . PL-treated during shelf-life studies, beef and tuna carpaccio showed significant, vacuum-packaged ham extended the shelf life by an additional remarkable difference in colour and odour when treated with PL at 30 days compared to the only vacuum-packaged ham, but the shelf 4.2 J/cm and above. Changes in a* and b* values were observed life of bologna was not extended by PL (Hierro et al., 2011). for RTE loin samples compared to Salchichon along the 28 days Apples treated with PL were susceptible to surface browning storage when PL of 11.9 J/cm was applied. Colour parameters were when compared to untreated samples (Moreira et al., 2017). PL not dramatically modified by PL treatment in these RTE dry-cured induces degradation of biopolymers in cell wall, affects the pectin products, which may be attributed to the greater stability of the present in the cell wall, and cells appeared collapsed with ruptured cured pigments in comparison to those of fresh meat (Ganan et al., membranes and thus causing a rupture and folding of cell walls. This 2013). membrane damage would increase in enzymatic browning reactions Ultraviolet light is known to induce a range of adverse effects like polyphenol oxidase activity due to greater tissue damage and in food products due to the generation of free radicals through a loss of functional cell compartmentalization (Gómez et al., 2012b). wide variety of photochemical reactions, which can damage vita- Gómez et al. (2012a) also found changes in total profile analysis, mins, antioxidants, while also inducing lipid oxidation and colour dynamic, and creep behaviour on apple surface due to PL treatment changes (Koutchma, 2009). One of the disadvantages of continuous and storage period. The use of PL at high fluences (28 J/cm ) UV light is the induction of oxidation processes in meat, which after- dramatically affects the final quality of fresh-cut mushrooms, and ward changes its sensorial properties (Paškevičiūtė and Lukšienė, thermal damage due to high PL doses seems to cause dehydration 2009; Paskeviciute et al., 2011). Wambura and Verghese (2011) also and major textural modification. Enzymatic inactivation in reported that PUV light treatment induced oxidation process, thus PL-treated samples flashed at that high dosage was also observed by making sample rancid during the storage time. The extent of lipid Oms-Oliu et al. (2010a). Similarly, Koh et al. (2016b) noticed that a peroxidation was found to be higher for vacuum-packaged chicken decrease in the pH and an increase in acidity were more pronounced frankfurters than unpackaged ones when treated at mild (5  s at for untreated samples compared to PL-treated fresh-cut cantaloupes, 13 cm) and moderate (30 s at 8 cm) UV treatment conditions (Keklik throughout the storage. Even, Koh et al. (2016a,b) found that there et al., 2009). A slight increase in lipid peroxidation was observed in was no effect on total soluble solids of fresh-cut cantaloupe at 4 the chicken meat after high-power PL treatment, whereas organo- ± 1°C due to decreased respiration rate in chilled storage. Colour leptic properties such as smell, odour, flavour, taste, or colour was not negatively affected by PL treatment for fruits and vegetables changes had no effect under non-thermal treatment conditions. At (Luksiene et al., 2012; Ignat et al., 2014; Agüero et al., 2016; Koh et higher exposure dose (>5.4 J/cm ), thermal effects were induced al., 2016a). However, change in colour of the endive salad and fresh- and also changes in organoleptic properties of chicken breast meat cut avocados was more pronounced as the fluence applied intensified was noticed (Paskeviciute et  al., 2011). Lipid peroxidation in dry- (Kramer et al., 2015), leading to browning during storage and firmness fermented salami was not noticed immediately after PL treatment, was significantly affected (Ramos-Villarroel et al., 2011). In contrast, whereas in chicken breast meat, it was found immediately (Rajkovic PL had a positive effect on colour and appearance of mung bean et  al., 2017). Off-odour in PL-treated samples remained over the sprouts (Kramer et al., 2015). Raspberries treated with PL showed a 14-day storage period due to photophysical changes occurred on decrease in brightness and did not substantially change the redness fresh-cut apples, and overall quality of the PL-treated apple was of the fruit immediately after the treatment, but along the storage, lower than that of untreated ones (Moreira et al., 2017). Similarly, berries became darker red and decrease in brightness, and a similar fresh-cut melon submitted to UV-C light had a lesser degree of off- trend in the stability of firmness of the fruit was also observed (Xu flavour perception than that of the control during 14-day storage and Wu, 2016). Similarly, UV spectra affected the colour and texture time (Manzocco et al., 2011). Slight flavour changes were noted by on fresh-cut mushroom and cut avocados and therefore treating fresh Ignat et al. (2014) in apple slice exposed to a fluence of 17.5 kJ/cm produce with quality stabilizing agents (anti-browning and texture which was similar to those detected during 7-day storage of untreated stabilizers) before PL flashing can be recommended for extending ones. Lasagabaster et al. (2011) found that there was no significant the shelf life of a product (Ramos-Villarroel et al., 2012, 2014). A effect on rheological properties of egg and a slight burnt odour in higher dose of PL (>1.75 J/cm ) treatment had a slight effect on the the egg shell was noticed as a sensory parameter, which was also appearance, colour, and enhanced the formation of non-enzymatic not significant. Even, PUV treatment had no effect on egg quality browning products and in turn increase the oxidative stability of in terms of albumen height, eggshell strength, and the presence of egg pasta (Manzocco et al., 2014). Paskeviciute et al. (2011) and cuticle (Keklik et al., 2010). High doses of PL (>8.75 J/cm ) reduced Paškevičiūtė and Lukšienė (2009) mentioned that sensory properties Salmonella as a result of egg pasta heating or sample heating rather 196 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 than the germicidal effect of UV component of light and sensory cantaloupes lead to an increase in the total phenolics concentration assessors observed that the intensity of sulphur odour increased in and the antioxidant capacity, thereby improving the health-related samples exposed at 1.75 J/cm (Manzocco et al., 2014). In cheddar characteristic of the product (Agüero et al., 2016; Koh et al., 2016b). cheese, PL did not affect the colour and lipid peroxidation during High-power PL treatment did not affect the AAC in fruits and had a refrigerated condition, but panelists scored the PL-treated samples negligible effect on total phenolic content (TPC) in fresh fruits and lower than the untreated ones for the sensory attributes such as vegetables (Luksiene et al., 2012; Charles et al., 2013; Koh et al., overall liking, flavour, and appearance. However, a dose of 9.22 2016a). TPC was not affected right after the treatment, whereas dur- J/cm had an adverse effect on organoleptic properties of cheese ing 10-day storage it was found to be decreasing significantly and at (Proulx et al., 2017). Similarly, a significant difference in odour and the end of the storage, PL did not improve nor affect the TPC levels flavour in the cheese slices treated with 4.2 and 8.4 J/cm shows in raspberries (Xu and Wu, 2016). The total anthocyanin content the presence of sulphur notes and the difference in decontamination (TAC) of raspberry was not influenced by PL at 5 and 15 s; surpris- magnitude between types of cheese which could be explained by ingly, PL-treated berries showed higher TAC compared to the control their different topography that is porous nature in Manchego vs at the end of the 10-day storage. However, PL at 30 s increased the smooth in Gouda type of cheeses (Fernández et al., 2016). Gómez- TAC by 10.1 mg cyanidin-3-glucoside equivalents/100 g fruit, when Lopez et al. (2005) mentioned that the presence of sensory attributes compared to 5 s treatment which could be due to stimulation of such as off-odours in IPL-flashed minimally processed white cabbage colour and anthocyanin accumulation by PL (Xu and Wu, 2016). and overall visual quality in Iceberg lettuce limited the shelf life to 7 The respiration rate was increased by the production of CO and and 3 days, respectively. O consumption at a higher rate when PL was applied on spinach The PL treatment affected the textural properties, firmness and fresh-cut cantaloupe (Agüero et al., 2016; Koh et al., 2016a). of fruit and vegetables (Luksiene et al., 2012; Xu and Wu, 2016; Similarly, partial pressures of O and CO inside the packages of 2 2 Moreira et al., 2017). Firmness values reported by Ramos-Villarroel tomato slices were significantly affected by PL processing (Valdivia- et al. (2014) showed that fresh-cut avocado treated at 305–1100 Nájar et al., 2017). These changes could be associated with a physi- nm were lower than those of samples treated at 400–1100 nm over ological stress or even physiological damage caused by the IPL the entire 15-day storage period, although their differences were not treatment, which in turn could affect the metabolic activity of the statistically significant. The application of UV-C light on fresh-cut vegetable/fruit tissue (Agüero et al., 2016). IPL treatment increased melon had no differences in colour and firmness up to 3 days of stor - the respiration rate and gas concentration of lettuce and fresh-cut age as the leakage of intercellular liquids from UV-C light-treated mushroom at the end of the storage, and the O level was <2%, samples was significantly lower than the control. Thus, UV-C light indicating anaerobic respiration of product in turn affecting the sen- treatment appears to be capable of increasing the dehydration of a sory quality/properties of the product (Gómez-Lopez et al., 2005; thin surface layer of melon cubes without affecting its overall firm- Ramos-Villarroel et al., 2012). Likewise, during storage conditions, ness and odour. It can be inferred that this phenomenon may cause respiration rate of IPL-treated fresh-cut avocados increased and thus the formation of a thin dried film hindering juice leakage during caused an undesirable anaerobic condition leading to the fermenta- the first 3 days of storage (Manzocco et al., 2011). PL treatment tion process in the fruit or triggering anaerobic metabolism of the maintained the colour, firmness, and carotenoid content of fresh-cut stored product which in turn lead to increase in ethanol production mangoes (Charles et al., 2013). Strawberries treated with PL did not and inhibiting ethylene production (Ramos-Villarroel et al., 2011). show pronounced softening when compared to untreated samples In contrast, Oms-Oliu et al. (2010a), Koh et al. (2016b), and Kramer even after 8 days of storage at 6°C, and cell wall strengthening of et al. (2015) did not observe any significant effect of CO by PL the fruit was induced by PL stress (Duarte-Molina et al., 2016). application in fresh-cut mushrooms, cantaloupe, and mung bean Similarly, firmness retention was also observed on PL-treated fresh- sprouts, respectively. cut cantaloupe compared to untreated samples during the storage, which may be due to the thickness of the sample (~3 cm) as the Combination Processing With PL effect of PL is restricted to the surface of the product (Koh et al., 2016a,b). But contrarily, the adverse effect of single PL treatment at The limitations of PL processing are uneven exposure, shadowing 11.7 J/cm on tissue structure of fresh-cut cantaloupes under chilled effect, browning, and sample heating. Many technologies/strategies storage was minimized by applying repetitive PL (RPL) treatment have been developed to address and challenge the limits of process- at 0.9 J/cm every 48-h interval leading to increased microbiologi- ing, increase the inactivation efficacy, maintain the quality of foods, cal quality, retention of firmness, and ascorbic acid content (AAC). and finally obtain minimally processed foods (Señorans et al., 2003). Further more, firmness was higher for fresh-cut cantaloupes treated Application of an anti-browning dipping treatment in combination with RPL compared to the untreated fresh-cut cantaloupes through- with IPL would increase the shelf life of minimally processed vegeta- out storage that may be due to lower CO concentration in treated bles and fruits (Gómez-Lopez et al., 2005). The use of ascorbic acid samples that could otherwise decompartmentalize the enzyme and (AC) at 1% on sliced mushroom before flashing at 4.8 and 12 J/cm their substrates which then act on cell walls of fruits tissue leading to significantly reduced browning during storage (Oms-Oliu et al., rapid deterioration (Koh et al., 2016b). 2010). To minimize the browning on PL-irradiated apple surface, PL treatment did not have any effect on the antioxidant activity AC/calcium chloride solution was used as an anti-browning of fruits and vegetables (Luksiene et al., 2012; Moreira et al., 2017). dipping prior to PL treatment (Gómez et al., 2012a). Further, this AAC was conserved throughout the storage period when treated at combination of AC + PL–treated apples showed greater microbial low fluences (2.7 and 7.8 J/cm ) in fresh-cut cantaloupe (Koh et al., growth after 7-day refrigerated storage than PL alone which could 2016a). A slight increase in AAC after RPL treatment was noticed be due to tissue damage and antioxidant capacity of AC that affect and even maintained throughout the storage, which could be due the damage caused by PL on microbes. In a similar study conducted to abiotic stress exerted by PL irradiation on fresh-cut cantaloupes by Moreira et al. (2017), pectin-coated fresh-cut apples that were (Koh et al., 2016b). IPL applied on spinach and RPL on fresh-cut exposed to PL were found to have the highest reduction in the Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 197 microbial count during storage, but the combination was not found application of US and PL was extended throughout storage com- to be antagonistic. The combined application of the edible coating pared to fresh untreated juice (Ferrario et al., 2015b). [gellan-gum–based (0.5% w/v) coating enriched with apple fibre] and The sequence of high-intense pulsed light (HIPL)/PEF resulted PL (12 J/cm ) treatment retarded the microbiological deterioration in a slight lowering of E.  coli K12 cells in apple juice compared of fresh-cut apples, reduced softening, and browning during 14 to PEF/HIPL, and the combination had no effect on quality days of storage at 4°C (Moreira et al., 2015). Dipping of fresh-cut parameters except for slight colour changes. HIPL/PEF treatment apples in AC/calcium chloride solution preceding to pectin coating had a significant effect on sensory attributes such as flavour and followed by PL treatment was more efficient in minimizing and odour of the non-thermally treated apple juice compared to browning, retaining antioxidant activity, and even did not have any thermally pasteurized control (Caminiti et  al., 2011b). Caminiti effect on microbial loads and sensory acceptability of apple cubes. et  al. (2011a) reported that light-based technology (UV/HIPL) Firmness was also maintained in fresh-cut apples when treated combined with PEF had no effect on colour, flavour, non-enzymatic with AC/calcium chloride solution that would help in cross-linking browning, TPC, and TAC of an apple and cranberry juice blend the polymer matrix and thus delaying softening of apple surfaces and received similar sensory score to that of pasteurized samples, (Moreira et al., 2017). The treatments combining PL (12 J/cm ) and whereas combination with manothermosonication (MTS) malic acid (MA) of 2% v/v resulted in significantly greater inhibition adversely affected overall acceptability and product quality. of L. innocua and E. coli populations than either PL or MA alone, Similarly, Caminiti et  al. (2012) found no change in colour, by achieving more than 5 log reductions for fresh produces such browning, and anthocyanin content of orange and carrot juice 2 2 as fresh-cut avocado, watermelon, and mushroom throughout the blend treated with either PEF, UV (10.6 J/cm ) or HIPL (3.3 J/cm ), storage period. Even, TEM observations demonstrated that damage, with MTS (400 kPa, 35°C, 1000 W, 20 kHz). Muñoz et al. (2011) especially to E. coli cells, was caused by a combination of treatments concluded that HIPL and thermosonication (TS) in combination due to agglutination of cytoplasmic content and disruption of cell irrespective of the sequence applied had an additive effect on E. coli membrane thus leading to microbial death (Ramos-Villarroel et al., inactivation in orange juices when compared to either of the technol- 2015). The combination of PL and MA dipping of mango slices ogy as a stand-alone. US in conjunction with PL treatment exhibited was found to be additive leading to a maximum reduction of 4.49 an inactivation equal to the sum of both effects taken separately (6.3, log cycle for L. innocua compared to PL alone (2.5 log CFU/g). It 5.9, and 3.7 log reduction for S. enteritidis, E. coli, and S. cerevisiae, is noteworthy that combination of PL, MA, and alginate coating respectively) in commercial apple juice. Delay in mould and yeast (ALC) lowered the inactivation level at the same time, and ALC acted recovery was observed due to the additive effect of US + PL during as an antagonistic factor which limited the effect of MA and PL. the 10-day storage period and prevented apple juice from turning Therefore, Salinas-Roca et al. (2016) concluded that PL should be darker and brownish (Ferrario and Guerrero, 2016). The combina- applied before ALC and MA treatment to overcome the interference tion of PL (low fluence—51.5 J/ml) as a first hurdle followed by TS caused by ALC. And, the highest inactivation of moulds, yeast, and led to significantly higher inactivation of E. coli than TS as the first psychrophilic bacteria was obtained with PL–ALC–MA treatment hurdle. The combination of PL and TS showed an additive effect on that showed the best microbial quality of mango slices during the inactivation of E.  coli than any of these hurdles applied individual storage, and also ALC helped to maintain the integrity of fruit by which could be due to the influence of treatment on different targets reducing the presence of exudates. that is DNA for PL and cell membrane for TS (Muñoz et al., 2012). Maftei et  al. (2014) stated that studies should be aimed at Muñoz et al. (2011) reported that there was no evidence of sublethal evaluating strategies based on the combination of PL treatments damage of cells with HIPL and TS applied individually or in com- with other minimal processing technologies, e.g. addition of natu- bination, but sublethal injury was detected by Muñoz et al. (2012) ral preservatives or mild heat treatment, in order to successfully when PL (low—4.03 J/cm ) was applied as the first hurdle with TS tackle safety issues for clarified juices treated with PL technology. compared to PL (high—5.1 J/cm ) treatment as a first hurdle. Combined effect of PL + nisin treatment in RTE sausages, resulted The combination of wet PL and 1% H O was found to be 2 2 in a significantly higher reduction of L.  innocua compared with the most efficient treatment for inactivating Salmonella on individual treatment (PL alone—1.37 and nisin dip alone—2.35 log raspberries and blueberries by >5.6 log CFU/g (Huang et al., CFU), thus suggesting an additive effect of PL and nisin of 4.03 log 2015). Dip-inoculated green onions were treated using PL (60 s), CFU (Uesugi and Moraru, 2009). Non-thermal PL treatment inacti- surfactant (sodium dodecyl sulphate, SDS)–sanitizer combination vation tests against L. innocua inoculated on modified chitosan con- washing (10 ppm chlorine + 1000 ppm SDS and 300 ppm H O 2 2 taining a nanoemulsion of mandarin essential oil-coated green beans + 1000 ppm SDS) as well as PL–surfactant–sanitizer combination 5 2 showed that 1.2 × 10 J/m per bean side was able to cause a reduc- (10 ppm chlorine + 1000 ppm SDS + 60 s PL and 300 ppm H O 2 2 tion of about 2 log cycles. However, PL did not show any synergistic + 1000 ppm SDS + 60 s PL). Different inactivation efficiency has antimicrobial effect against L. innocua throughout the storage and been observed in various structures of green onions (Figure 5). colour properties had a slight detrimental impact with browning The combination of wet PL treatment with chlorine washing spots formation on the samples (Donsì et al., 2015). Furthermore, a had an additive effect on E. coli inactivation of about 2.4 log 6 log cycle in yeast reduction was observed by Ferrario et al. (2015b) reduction when compared to chlorine washing or PL alone. PL when PL was applied prior to US treatment for both commercial combined with SDS; surfactant was better effective compared and naturally squeezed apple juice. Similarly, Ferrario and Guerrero to PL and chlorine combination showing the synergistic effect (2017) also achieved S.  cerevisiae KE 162 inactivation of 5.8 and of surfactant. Hydrogen peroxide was slightly more efficient in 6.4 log reduction in commercial and naturally squeezed apple juice inactivation of E. coli on green onions (0.7 to 2.6 log CFU/g) respectively, even though US treatment was applied before PL. than thymol and citric acid combined with 60 s PL treatment. Whereas, US applied before PL treatment did not contribute signifi- PL–surfactant–sanitizer combination had no additive effect when cant inactivation for A.  acidoterrestris spore in apple juice matrix. compared to PL plus surfactant combination (Xu et al., 2013). These combinations showed an additive effect on inactivation and PL is more efficient in reducing microbial loads on a fresh-cut storage studies revealed that the level of inactivation reached by the salad than similar treatments in electrolyzed water (400 ppm free 198 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 Figure 5. Combined effect of PL–surfactant–sanitizer on the inactivation of E. coli O157:H7 on dip-inoculated green onions. The initial populations of E. coli O157:H7 for dip inoculated stems and leaves were 4.5 and 5.5 log10 CFU/g, respectively. Values in stems group marked by the same capital letter were not significantly different (P > 0.05). Values in leaves group marked by the same lowercase letter were not significantly different (P > 0.05) (Xu et al., 2013). chlorine) or chlorine dioxide (15 ppm). PL may, therefore, be as physical and chemical properties of the liquid foods affects the an appropriate measure to reduce the required amount of fresh occurrence of lethal and sublethal effects induced by PL treatment. water in fresh produce processing and to keep microbial loads in the wash water on a low level (Kramer et al., 2017). Therefore, PL Acknowledgement in combination with other technologies can be a novel technology The authors thank the Director, CSIR-CFTRI, Mysore, India. M.L. Bhavya for producing minimally processed foods without compromising thank UGC, New Delhi for UGC-NET fellowship. the nutritional and sensorial quality of foods. Conflict of interest statement. None declared. Conclusion References PL being one among the novel food-processing techniques has the Agüero, M. V., Jagus, R. J., Martín-Belloso, O., Soliva-Fortuny, R. (2016). ability to reduce the deleterious effects that thermal processing and Surface decontamination of spinach by intense pulsed light treatments: traditional processing methods have on the colour, texture, flavour, Impact on quality attributes. Postharvest Biology and Technology 121: and nutritive value of foods. The novel emerging PL technology 118–125. is finding application in the food industry with a broad scope in Anderson, J. G., Rowan, N. J., MacGregor, S. J., Fouracre, R. A., Farish, O. improving nutritional and organoleptic properties and also extend- (2000). Inactivation of food-borne enteropathogenic bacteria and spoilage ing shelf life of food. Novel technologies are considered to be a fungi using pulsed-light. IEEE Transactions on Plasma Science 28: 83–88. very promising alternative to conventional processing techniques. Artíguez, M. L., Lasagabaster, A., de Marañón, I. M. (2011). Factors affecting microbial inactivation by pulsed light in a continuous flow-through unit A distinct advantage of light-based techniques for certain operating for liquid products treatment. Procedia Food Science 1: 786–791. parameters is the inactivation of microorganisms with maintaining Bialka, K. L., Demirci, A. (2007). Decontamination of Escherichia coli of the foods’ sensory attributes and minimal quality loss. One of the O157:H7 and Salmonella enterica on blueberries using ozone and pulsed disadvantages of PL is high investment costs (€300 000–800 000) UV-light. Journal of Food Science 72: M391–M396. and PL is an inappropriate technology for cereals, grains, and spices Bialka, K. L., Demirci, A. (2008). Efficacy of pulsed UV-light for the due to their opaque nature, uneven surfaces, crevices, or pores decontamination of Escherichia coli O157:H7 and Salmonella spp. on because of the ability of microorganisms to harbour in minor open- raspberries and strawberries. Journal of Food Science 73: M201–M207. ings, whereas it is an efficient method of decontaminating packag- Bialka, K. L., Demirci, A., Puri, V. M. (2008). Modeling the inactivation of ing materials, surface of foods and liquids. Therefore, light-based Escherichia coli O157: H7 and Salmonella enterica on raspberries and technology with slight alteration by the addition of cooling systems strawberries resulting from exposure to ozone or pulsed UV-light. Journal of Food Engineering 85: 444–449. in order to minimize the thermal effect can be a promising technique Caminiti, I. M., Noci, F., Morgan, D. J., Cronin, D. A., Lyng, J. G. (2012). to inactivate the microbes in plant-derived foods, including both The effect of pulsed electric fields, ultraviolet light or high intensity light solid and liquids by retaining the quality of foods and increasing pulses in combination with manothermosonication on selected physico- the shelf life of the products. And, light-based processing of animal chemical and sensory attributes of an orange and carrot juice blend. Food products with proper packaging material has an application in the and Biproducts Processing 90: 442–448. food industry by increasing the shelf life and even maintaining the Caminiti, I. M., et al. (2011a). Impact of selected combinations of non-thermal organoleptic properties of food throughout the storage. In future, processing technologies on the quality of an apple and cranberry juice more research is required for a more comprehensive understand- blend. Food Chemistry 124: 1387–1392. ing of inactivation mechanism of Gram-positive and Gram-negative Caminiti, I. M., et  al. (2011b). The effect of pulsed electric fields (PEF) in bacteria by PL, how the fluence, type of microbial strain, as well combination with high intensity light pulses (HILP) on Escherichia coli Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 199 inactivation and quality attributes in apple juice. Innovative Food Science Ferrario, M., Guerrero, S., Alzamora, S. M. (2014). Study of pulsed light- and Emerging Technologies 12: 118–123. induced damage on Saccharomyces cerevisiae in apple juice by flow Chaine, A., Levy, C., Lacour, B., Riedel, C., Carlin, F. (2012). Decontamination cytometry and transmission electron microscopy. Food and Bioprocess of sugar syrup by pulsed light. Journal of Food Protection 75: 913–917. Technology 7: 1001–1011. Charles, F., Vidal, V., Olive, F., Filgueiras, H., Sallanon, H. (2013). Pulsed light Fine, F., Gervais, P. (2004). Efficiency of pulsed UV light for microbial treatment as new method to maintain physical and nutritional quality of decontamination of food powders. Journal of Food Protection 67: 787– fresh-cut mangoes. Innovative Food Science and Emerging Technologies 792. 18: 190–195. Food and Drug Administration. (1996). Pulsed Light for the Treatment of Chawla, R., Patil, G. R., Singh, A. K. (2011). High hydrostatic pressure Food, 21CFR179.4. technology in dairy processing: A  review. Journal of Food Science and Ganan, M., Hierro, E., Hospital, X. F., Barroso, E., Fernández, M. (2013). Use Technology 48: 260–268. of pulsed light to increase the safety of ready-to-eat cured meat products. Cheigh, C. I., Hwang, H. J., Chung, M. S. (2013). Intense pulsed light (IPL) and Food Control 32: 512–517. UV-C treatments for inactivating Listeria monocytogenes on solid medium Gómez, P. L., García-Loredo, A., Nieto, A., Salvatori, D. M., Guerrero, and seafoods. Food Research International 54: 745–752. S., Alzamora, S. M. (2012a). Effect of pulsed light combined with an Cheigh, C. I., Park, M. H., Chung, M. S., Shin, J. K., Park, Y. S. (2012). antibrowning pretreatment on quality of fresh cut apple. Innovative Food Comparison of intense pulsed light-and ultraviolet (UVC)-induced cell Science and Emerging Technologies 16: 102–112. damage in Listeria monocytogenes and Escherichia coli O157: H7. Food Gómez, P. L., Salvatori, D. M., García-Loredo, A., Alzamora, S. M. (2012b). Control 25: 654–659. Pulsed light treatment of cut apple: Dose effect on color, structure, and Choi, M. S., Cheigh, C. I., Jeong, E. A., Shin, J. K., Chung, M. S. (2010). microbiological stability. Food and Bioprocess Technology 5: 2311–2322. Nonthermal sterilization of Listeria monocytogenes in infant foods by Gómez-López, V. M., Devlieghere, F., Bonduelle, V., Debevere, J. (2005). Intense intense pulsed-light treatment. Journal of Food Engineering 97: 504–509. light pulses decontamination of minimally processed vegetables and their Chun, H. H., Kim, J. Y., Song, K. B. (2010). Inactivation of foodborne shelf-life. International Journal of Food Microbiology 103: 79–89. pathogens in ready-to-eat salad using UV-C irradiation. Food Science and Gomez-Lopez, V. M., Ragaert, P., Debevere, J., Devlieghere, F. (2007). Pulsed Biotechnology 19: 547–551. light for food decontamination: a  review. Trends in Food Science and Chun, H., Kim, J., Chung, K., Won, M., Song, K. B. (2009). Inactivation kinetics Technology 18: 464–473. of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Hierro, E., Barroso, E., De la Hoz, L., Ordóñez, J. A., Manzano, S., Fernández, Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation. M. (2011). Efficacy of pulsed light for shelf-life extension and inactivation Meat Science 83: 599–603. of Listeria monocytogenes on ready-to-eat cooked meat products. Devlieghere, F., Vermeiren, L., Debevere, J. (2004). New preservation Innovative Food Science and Emerging Technologies 12: 275–281. technologies: possibilities and limitations. International Dairy Journal 14: Hierro, E., Ganan, M., Barroso, E., Fernández, M. (2012). Pulsed light 273–285. treatment for the inactivation of selected pathogens and the shelf-life Donsì, F., et al. (2015). Green beans preservation by combination of a modified extension of beef and tuna carpaccio. International Journal of Food chitosan based-coating containing nanoemulsion of mandarin essential oil Microbiology 158: 42–48. with high pressure or pulsed light processing. Postharvest Biology and Hierro, E., Manzano, S., Ordóñez, J. A., de la Hoz, L., Fernández, M. (2009). Technology 106: 21–32. Inactivation of Salmonella enterica serovar enteritidis on shell eggs by Duarte-Molina, F., Gómez, P. L., Castro, M. A., Alzamora, S. M. (2016). pulsed light technology. International Journal of Food Microbiology 135: Storage quality of strawberry fruit treated by pulsed light: Fungal decay, 125–130. water loss and mechanical properties. Innovative Food Science and Hilton, S. T., de Moraes, J. O., Moraru, C. I. (2017). Effect of sublethal Emerging Technologies 34: 267–274. temperatures on pulsed light inactivation of bacteria. Innovative Food Dunn, J., Ott, T., Clark, W. (1995). Pulsed-light treatment of food and Science and Emerging Technologies 39: 49–54. packaging. Food Technology 49: 95–98. Huang, Y., Chen, H. (2014). A novel water-assisted pulsed light processing for Elmnasser, N., Guillou, S., Leroi, F., Orange, N., Bakhrouf, A., Federighi, M. decontamination of blueberries. Food Microbiology 40: 1–8. (2007). Pulsed-light system as a novel food decontamination technology: Huang, Y., Sido, R., Huang, R., Chen, H. (2015). Application of water-assisted A review. Canadian Journal of Microbiology 53: 813–821. pulsed light treatment to decontaminate raspberries and blueberries from Fernández, M., Arias, K., Hierro, E. (2016). Application of pulsed light to sliced Salmonella. International Journal of Food Microbiology 208: 43–50. cheese: Effect on listeria. Food and Bioprocess Technology 9: 1335–1344. Huang, Y., Ye, M., Cao, X., Chen, H. (2017). Pulsed light inactivation of Ferrario, M., Alzamora, S. M., Guerrero, S. (2013). Inactivation kinetics of murine norovirus, Tulane virus, Escherichia coli O157:H7 and Salmonella some microorganisms in apple, melon, orange and strawberry juices by in suspension and on berry surfaces. Food Microbiology 61: 1–4. high intensity light pulses. Journal of Food Engineering 118: 302–311. Hwang, H. J., Cheigh, C. I., Chung, M. S. (2015). Relationship between optical Ferrario, M., Alzamora, S. M., Guerrero, S. (2015a). Study of pulsed light properties of beverages and microbial inactivation by intense pulsed light. inactivation and growth dynamics during storage of Escherichia coli Innovative Food Science and Emerging Technologies 31: 91–96. ATCC 35218, Listeria innocua ATCC 33090, Salmonella enteritidis Hwang, H. J., Cheigh, C. I., Chung, M. S. (2017). Construction of a pilot-scale MA44 and Saccharomyces cerevisiae KE162 and native flora in apple, continuous-flow intense pulsed light system and its efficacy in sterilizing orange and strawberry juices. International Journal of Food Science and sesame seeds. Innovative Food Science and Emerging Technologies 39: Technology 50: 2498–2507. 1–6. Ferrario, M., Alzamora, S. M., Guerrero, S. (2015b). Study of the inactivation Ignat, A., Manzocco, L., Maifreni, M., Bartolomeoli, I., Nicoli, M. C. (2014). of spoilage microorganisms in apple juice by pulsed light and ultrasound. Surface decontamination of fresh-cut apple by pulsed light: Effects Food Microbiology 46: 635–642. on structure, colour and sensory properties. Postharvest Biology and Ferrario, M., Guerrero, S. (2016). Effect of a continuous flow-through pulsed Technology 91: 122–127. light system combined with ultrasound on microbial survivability, color Innocente, N., et  al. (2014). Effect of pulsed light on total microbial count and sensory shelf life of apple juice. Innovative Food Science and Emerging and alkaline phosphatase activity of raw milk. International Dairy Journal Technologies 34: 214–224. 39: 108–112. Ferrario, M., Guerrero, S. (2017). Impact of a combined processing technology Kaack, K., Lyager, B. (2007). Treatment of slices from carrot (Daucus carota) involving ultrasound and pulsed light on structural and physiological using high intensity white pulsed light. European Food Research and changes of Saccharomyces cerevisiae KE 162 in apple juice. Food Technology 224: 561–566. Microbiology 65: 83–94. Keklik, N. M., Demirci, A., Puri, V. M. (2009). Inactivation of Listeria monocytogenes on unpackaged and vacuum-packaged chicken 200 M. L. Bhavya and H. Umesh Hebbar, 2017, Vol. 1, No. 3 frankfurters using pulsed UV-light. Journal of Food Science 74: M431– Moreira, M. R., Álvarez, M. V., Martín-Belloso, O., Soliva-Fortuny, R. (2017). M439. Effects of pulsed light treatments and pectin edible coatings on the quality Keklik, N. M., Demirci, A., Patterson, P. H., Puri, V. M. (2010). Pulsed UV light of fresh-cut apples: A hurdle technology approach. Journal of the Science inactivation of Salmonella enteritidis on eggshells and its effects on egg of Food and Agriculture 97: 261–268. quality. Journal of Food Protection 73: 1408–1415. Moreira, M. R., Tomadoni, B., Martín-Belloso, O., Soliva-Fortuny, R. (2015). Koh, P. C., Noranizan, M. A., Karim, R., Nur Hanani, Z. A. (2016a). Preservation of fresh-cut apple quality attributes by pulsed light in Microbiological stability and quality of pulsed light treated cantaloupe combination with gellan gum-based prebiotic edible coatings. LWT-Food (Cucumis melo L. reticulatus cv. Glamour) based on cut type and light Science and Technology 64: 1130–1137. fluence. Journal of Food Science and Technology 53: 1798–1810. Muñoz, A., et al. (2012). Effects on Escherichia coli inactivation and quality Koh, P. C., Noranizan, M. A., Karim, R., Hanani, Z. A. N. (2016b). Repetitive attributes in apple juice treated by combinations of pulsed light and pulsed light treatment at certain interval on fresh-cut cantaloupe (Cucumis thermosonication. Food Research International 45: 299–305. melo L. reticulatus cv. Glamour). Innovative Food Science and Emerging Muñoz, A., et  al. (2011). Combinations of high intensity light pulses and Technologies 36: 92–103. thermosonication for the inactivation of Escherichia coli in orange juice. Koutchma, T. (2009). Advances in ultraviolet light technology for non-thermal Food Microbiology 28: 1200–1204. processing of liquid foods. Food and Bioprocess Technology 2: 138–155. Nicorescu, I., Nguyen, B., Moreau-Ferret, M., Agoulon, A., Chevalier, S., Kramer, B., Wunderlich, J., Muranyi, P. (2015). Pulsed light decontamination of Orange, N. (2013). Pulsed light inactivation of Bacillus subtilis vegetative endive salad and mung bean sprouts and impact on color and respiration cells in suspensions and spices. Food Control 31: 151–157. activity. Journal of Food Protection 78: 340–348. Norton, T., Sun, D. W. (2008). Recent advances in the use of high pressure as an Kramer, B., Wunderlich, J., Muranyi, P. (2017). Pulsed light decontamination effective processing technique in the food industry. Food and Bioprocess of endive salad and mung bean sprouts in water. Food Control 73: 367– Technology 1: 2–34. 371. Oms-Oliu, G., Aguiló-Aguayo, I., Martín-Belloso, O., Soliva-Fortuny, R. Krishnamurthy, K., Demirci, A., Irudayaraj, J. M. (2007). Inactivation of (2010a). Effects of pulsed light treatments on quality and antioxidant Staphylococcus aureus in milk using flow-through pulsed UV-light properties of fresh-cut mushrooms (Agaricus bisporus). Postharvest treatment system. Journal of Food Science 72: M233–M239. Biology and Technology 56: 216–222. Krishnamurthy, K., Tewari, J. C., Irudayaraj, J., Demirci, A. (2010). Microscopic Oms-Oliu, G., Martín-Belloso, O., Soliva-Fortuny, R. (2010b). Pulsed and spectroscopic evaluation of inactivation of Staphylococcus aureus by light treatments for food preservation. A  review. Food and Bioprocess pulsed UV light and infrared heating. Food and Bioprocess Technology Technology 3: 13. 3: 93. Orlowska, M., Koutchma, T., Grapperhaus, M., Gallagher, J., Schaefer, R., Lasagabaster, A., de Marañón, I. M. (2012). Sensitivity to pulsed light Defelice, C. (2013). Continuous and pulsed ultraviolet light for nonthermal technology of several spoilage and pathogenic bacteria isolated from fish treatment of liquid foods. Part 1: Effects on quality of fructose solution, products. Journal of Food Protection 75: 2039–2044. apple juice, and milk. Food and Bioprocess Technology 6: 1580–1592. Lasagabaster, A., de Marañón, I. M. (2014). Survival and growth of Listeria Ortega-Rivas, E., Salmerón-Ochoa, I. (2014). Nonthermal food processing innocua treated by pulsed light technology: Impact of post-treatment alternatives and their effects on taste and flavor compounds of beverages. temperature and illumination conditions. Food Microbiology 41: 76–81. Critical Reviews in Food Science and Nutrition 54: 190–207. Lasagabaster, A., Arboleya, J. C., De Maranon, I. M. (2011). Pulsed light Otaki, M., Okuda, A., Tajima, K., Iwasaki, T., Kinoshita, S., Ohgaki, S. (2003). technology for surface decontamination of eggs: Impact on Salmonella Inactivation differences of microorganisms by low pressure UV and pulsed inactivation and egg quality. Innovative Food Science and Emerging Tech- xenon lamps. Water Science and Technology 47: 185–190. nologies 12: 124–128. Ozer, N. P., Demirci, A. (2006). Inactivation of Escherichia coli O157: H7 Levy, C., Aubert, X., Lacour, B., Carlin, F. (2012). Relevant factors affecting and Listeria monocytogenes inoculated on raw salmon fillets by pulsed microbial surface decontamination by pulsed light. International Journal UV-light treatment. International Journal of Food Science and Technology of Food Microbiology 152: 168–174. 41: 354–360. Luksiene, Z., Buchovec, I., Kairyte, K., Paskeviciute, E., Viskelis, P. (2012). Palgan, I., et  al. (2011). Effectiveness of high intensity light pulses (HILP) High-power pulsed light for microbial decontamination of some fruits treatments for the control of Escherichia coli and Listeria innocua in apple and vegetables with different surfaces. Journal of Food, Agriculture and juice, orange juice and milk. Food Microbiology 28: 14–20. Environment 10: 162–167. Paškevičiūtė, E., Lukšienė, Ž. (2009). High-power pulsed light for MacGregor, S. J., Rowan, N. J., Mcllvaney, L., Anderson, J. G., Fouracre, R. A., decontamination of chicken breast surface. Cheminė Technologija 4: 53. Farish, O. (1998). Light inactivation of food-related pathogenic bacteria Paskeviciute, E., Buchovec, I., Luksiene, Z. (2011). High-power pulsed using a pulsed power source. Letters in Applied Microbiology 27: 67–70. light for decontamination of chicken from food pathogens: A  study on Maftei, N. A., Ramos-Villarroel, A. Y., Nicolau, A. I., Martín-Belloso, O., antimicrobial efficiency and organoleptic properties. Journal of Food Soliva-Fortuny, R. (2014). Influence of processing parameters on the Safety 31: 61–68. pulsed-light inactivation of Penicillium expansum in apple juice. Food Pataro, G., Muñoz, A., Palgan, I., Noci, F., Ferrari, G., Lyng, J. G. (2011). Control 41: 27–31. Bacterial inactivation in fruit juices using a continuous flow pulsed light Manzocco, L., Da Pieve, S., Maifreni, M. (2011). Impact of UV-C light on (PL) system. Food Research International 44: 1642–1648. safety and quality of fresh-cut melon. Innovative Food Science and Pereira, R. N., Vicente, A. A. (2010). Environmental impact of novel thermal Emerging Technologies 12: 13–17. and non-thermal technologies in food processing. Food Research Manzocco, L., et al. (2014). Effect of pulsed light on safety and quality of fresh International 43: 1936–1943. egg pasta. Food and Bioprocess Technology 7: 1973–1980. Proulx, J., et  al. (2017). Short communication: Influence of pulsed light Miller, B. M., Sauer, A., Moraru, C. I. (2012). Inactivation of Escherichia coli treatment on the quality and sensory characteristics of cheddar cheese. in milk and concentrated milk using pulsed-light treatment. Journal of Journal of Dairy Science 100: 1004–1008. Dairy Science 95: 5597–5603. Rajkovic, A., Tomasevic, I., De Meulenaer, B., Devlieghere, F. (2017). The effect Misra, N. N., Tiwari, B. K., Raghavarao, K. S.  M. S., Cullen, P. J. (2011). of pulsed UV light on Escherichia coli O157: H7, Listeria monocytogenes, Nonthermal plasma inactivation of food-borne pathogens. Food Salmonella Typhimurium, Staphylococcus aureus and staphylococcal Engineering Reviews 3: 159–170. enterotoxin A on sliced fermented salami and its chemical quality. Food Moreaua, M., Nicorescua, I., Turpina, A. S., Agoulonb, A., Chevaliera, S., Control 73: 829–837. Orangea, N. (2011). Decontamination of spices by using a pulsed light Ramos-Villarroel, A. Y., Aron-Maftei, N., Martín-Belloso, O., Soliva-Fortuny, treatment. In: Food Process Engineering in a Changing World, Proceedings R. (2012). The role of pulsed light spectral distribution in the inactivation of the 11th International Congress of Engineering and Food (pp. 22–26). of Escherichia coli and Listeria innocua on fresh-cut mushrooms. Food Control 24: 206–213. Pulsed light processing of foods for microbial safety, 2017, Vol. 1, No. 3 201 Ramos-Villarroel, A. Y., Martín-Belloso, O., Soliva-Fortuny, R. (2011). Bacterial Takeshita, K., et  al. (2003). Damage of yeast cells induced by pulsed light inactivation and quality changes in fresh-cut avocado treated with intense irradiation. International Journal of Food Microbiology 85: 151–158. light pulses. European Food Research and Technology 233: 395–402. Thirumdas, R., Sarangapani, C., Annapure, U. S. (2015). Cold plasma: A novel Ramos-Villarroel, A. Y., Martín-Belloso, O., Soliva-Fortuny, R. (2015). non-thermal technology for food processing. Food Biophysics 10: 1–11. Combined effects of malic acid dip and pulsed light treatments on the Tomašević, I. (2015). The effect of intense light pulses on the sensory inactivation of Listeria innocua and Escherichia coli on fresh-cut produce. quality and instrumental color of meat from different animal breeds. Food Control 52: 112–118. Biotechnology in Animal Husbandry 31: 273–281. Ramos-Villarroel, A., Aron-Maftei, N., Martín-Belloso, O., Soliva-Fortuny, R. Uesugi, A. R., Moraru, C. I. (2009). Reduction of listeria on ready-to-eat (2014). Bacterial inactivation and quality changes of fresh-cut avocados as sausages after exposure to a combination of pulsed light and nisin. Journal affected by intense light pulses of specific spectra. International Journal of of Food Protection 72: 347–353. Food Science and Technology 49: 128–136. US Food and Drug Administration. (2004). FDA Guidance to Industry, 2004: Rastogi, N. K. (2011). Opportunities and challenges in application of Recommendations to Processors of Apple Juice or Cider on the Use of ultrasound in food processing. Critical Reviews in Food Science and Ozone for Pathogen Reduction purposes. Nutrition 51: 705–722. Valdivia-Nájar, C. G., Martín-Belloso, O., Giner-Seguí, J., Soliva-Fortuny, R. Rowan, N. J., MacGregor, S. J., Anderson, J. G., Fouracre, R. A., McIlvaney, L., (2017). Modeling the inactivation of Listeria innocua and Escherichia Farish, O. (1999). Pulsed-light inactivation of food-related microorganisms. coli in fresh-cut tomato treated with pulsed light. Food and Bioprocess Applied and Environmental Microbiology 65: 1312–1315. Technology 10: 266–274. Salinas-Roca, B., Soliva-Fortuny, R., Welti-Chanes, J., Martín-Belloso, O. Wambura, P., Verghese, M. (2011). Effect of pulsed ultraviolet light on quality (2016). Combined effect of pulsed light, edible coating and malic acid of sliced ham. LWT-Food Science and Technology 44: 2173–2179. dipping to improve fresh-cut mango safety and quality. Food Control 66: Wang, C. Y., Huang, H. W., Hsu, C. P., Yang, B. B. (2016). Recent advances 190–197. in food processing using high hydrostatic pressure technology. Critical Sauer, A., Moraru, C. I. (2009). Inactivation of Escherichia coli ATCC 25922 Reviews in Food Science and Nutrition 56: 527–540. and Escherichia coil O157:H7 in apple juice and apple cider, using pulsed Xu, W., Wu, C. (2016). The impact of pulsed light on decontamination, quality, light treatment. Journal of Food Protection 72: 937–944. and bacterial attachment of fresh raspberries. Food Microbiology 57: Señorans, J., Ibáñez, E., Cifuentes, A. (2003). New trends in food processing. 135–143. Critical Reviews in Food Science and Nutrition 43: 507–526. Xu, W., Chen, H., Huang, Y., Wu, C. (2013). Decontamination of Escherichia coli Sharma, R. R., Demirci, A. (2003). Inactivation of Escherichia coli O157: O157:H7 on green onions using pulsed light (PL) and PL-surfactan-sanitizer H7 on inoculated alfalfa seeds with pulsed ultraviolet light and response combinations. International Journal of Food Microbiology 166: 102–108. surface modelling. Journal of Food Science 68: 1448–1453. Yi, J. Y., Bae, Y. K., Cheigh, C. I., Chung, M. S. (2017). Microbial inactivation Soliva-Fortuny, R., Balasa, A., Knorr, D., Martín-Belloso, O. (2009). Effects of and effects of interrelated factors of intense pulsed light (IPL) treatment for pulsed electric fields on bioactive compounds in foods: A review. Trends in Pseudomonas aeruginosa. LWT-Food Science and Technology 77: 52–59. Food Science and Technology 20: 544–556.

Journal

Food Quality and SafetyOxford University Press

Published: Oct 13, 2017

There are no references for this article.