Modeling Alkaline Phosphatase Inactivation in Bovine Milk During High-Temperature Short-Time Pasteurization

Abstract

Alkaline phosphatase (AP) is used as the indicator enzyme for proper pasteurization of bovine milk. Predictive modeling of AP inactivation during high-temperature short-time (HTST) pasteurization would support regulations; thus ensuring the safety of heat treated milk. Activation energy (Ea) of AP in milk was measured experimentally using the capillary tube method, and Ea was found to be 429252 J/mol. The Ea was used to develop a nonlinear model to describe the thermal inactivation of milk in a small-scale HTST pasteurizer with a plate heat exchanger. Integrated pasteurization effect (PE) was obtained at different holding temperatures (62–72°C) and holding times (3–25 s), by converting times at different temperatures in various sections of the pasteurizer to the equivalent time at the reference temperature (72°C). A nonlinear function was developed to relate the log(% residual AP activity) to PE. The r ² varied from 0.7488 to 0.8311. The validation trial indicated that the model could predict AP activity accurately for the% residual AP activity >1%.

Keywords

alkaline phosphatase inactivation high-temperature short-time pasteurization milk activation energy

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