Predictive modeling of lactoperoxidase and gamma-glutamyl transpeptidase inactivation in a high-temperature short-time pasteurizer

Linear models were derived to describe the thermal inactivation of gamma-glutamyl transpeptidase (GGTP) and lactoperoxidase (LP) in bovine milk in a high-temperature short-time (HTST) pilot scale pasteurizer. Integrated lethal effect (pasteurization effect; PE) was related by simple linear functions to the log(10) of the % initial activity with a power transformation of the PE values to improve linear fit. The PE values required for a 1-log reduction in GGTP and LP activity, calculated from the equation parameters were 5.46 and 26.5, respectively, suggesting that LP is considerably more heat stable than GGTP. The two linear equations were validated using data from additional trials. Greater variation was found with the LP assay as compared to the GGTP suggesting that the assay method requires improvement. These linear models can be incorporated into user-friendly software to facilitate the estimation of lethal effect achieved with other pasteurization equipment.