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Kinetic and thermodynamic parameters of alkaline phosphatase and γ—glutamyl transferase inactivation in bovine milk

Kinetic and thermodynamic parameters of alkaline phosphatase and γ—glutamyl transferase... Kinetic and thermodynamic studies were carried out at different time–temperature combinations in order to evaluate the suitability of alkaline phosphatase (ALP) and γ-glutamyl transferase (GGT) as markers for the heat treatment of milk. The average activities of the enzymes in bovine milk were 0.46 ± 0.02 U.mL−1 for ALP and 4.05 ± 0.26 and 4.55 ± 0.24 U.mL−1 for GGT in milk with different fat levels. A detailed comparative kinetic study of ALP inactivation was performed in the temperature range of 50 to 75 °C in raw whole milk and buffer in order to assess the stabilizing effect of milk compounds on ALP. The degree and rate of inactivation of GGT in raw cow’s milk with 1.5% and 2.5% fat were measured in the temperature range of 60 to 85 °C. Kinetic studies showed that the thermal inactivation of ALP and GGT followed first-order kinetics. The influence of temperature on the inactivation rate constant was quantified using the Arrhenius equation and was characterized by activation energy (E a) values of 214.09 ± 12.9 and 222.02 ± 5.6 kJ.mol−1 for inactivation of ALP in buffer and raw milk. For GGT, E a values ranged from 190.8 ± 6.06 to 183.7 ± 8.4 kJ.mol−1 for enzyme inactivation in low-fat milk and in milk containing 2.5% fat, respectively. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Dairy Science & Technology Springer Journals

Kinetic and thermodynamic parameters of alkaline phosphatase and γ—glutamyl transferase inactivation in bovine milk

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Publisher
Springer Journals
Copyright
Copyright © 2011 by INRA and Springer Science+Business Media B.V.
Subject
Chemistry; Microbiology; Agriculture; Food Science
ISSN
1958-5586
eISSN
1958-5594
DOI
10.1007/s13594-011-0028-3
Publisher site
See Article on Publisher Site

Abstract

Kinetic and thermodynamic studies were carried out at different time–temperature combinations in order to evaluate the suitability of alkaline phosphatase (ALP) and γ-glutamyl transferase (GGT) as markers for the heat treatment of milk. The average activities of the enzymes in bovine milk were 0.46 ± 0.02 U.mL−1 for ALP and 4.05 ± 0.26 and 4.55 ± 0.24 U.mL−1 for GGT in milk with different fat levels. A detailed comparative kinetic study of ALP inactivation was performed in the temperature range of 50 to 75 °C in raw whole milk and buffer in order to assess the stabilizing effect of milk compounds on ALP. The degree and rate of inactivation of GGT in raw cow’s milk with 1.5% and 2.5% fat were measured in the temperature range of 60 to 85 °C. Kinetic studies showed that the thermal inactivation of ALP and GGT followed first-order kinetics. The influence of temperature on the inactivation rate constant was quantified using the Arrhenius equation and was characterized by activation energy (E a) values of 214.09 ± 12.9 and 222.02 ± 5.6 kJ.mol−1 for inactivation of ALP in buffer and raw milk. For GGT, E a values ranged from 190.8 ± 6.06 to 183.7 ± 8.4 kJ.mol−1 for enzyme inactivation in low-fat milk and in milk containing 2.5% fat, respectively.

Journal

Dairy Science & TechnologySpringer Journals

Published: Jun 16, 2011

References