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Updated: Sep 9, 2026

Measuring Lactase Enzymatic Activity in the Teaching Lab
Published on: August 6, 2018
Inactivation kinetics of gamma-glutamyltransferase during the heating of milk
G Zehetner1, C Bareuther, T Henle
1Lehrstuhl für Milchwissenschaft, Technische Universität München, Freising-Weihenstephan, Germany.
Abstract:
The inactivation of gamma-glutamyltransferase (GGT, E.C.2.3.2.2) during the heating of milk to between 65.0 degrees C and 76.0 degrees C for periods of 5 s to 1000 s follows a first-order reaction (energy of activation 457 kJ/mol) and can be used to monitor the process of milk pasteurisation. GGT activity in raw milks from individual cows showed only little variation (5.92 +/- 0.59 units). Residual GGT activity in 17 commercial milks ranged between 1% and 20%, indicating a heat treatment at the upper limit of the permitted pasteurisation conditions.
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