Heat-Stable Microbial Peptidases Associated with the Microbiota of Raw Milk

This chapter focuses on the heat stability of indigenous (expressed from different bovine tissues and cells, then secreted into milk) and bacterial (exogenous) dairy enzymes as well as thermal and non-thermal inactivation methods. The fundamentals of heat inactivation kinetics are outlined and the heat stabilities of the following enzymes are discussed in detail: alkaline phosphatase, γ-glutamyltransferase, lactoperoxidase, lipoprotein lipase, cathepsin D, plasmin, and peptidases from Pseudomonas ssp. Based on the presented kinetic data of these enzymes, inactivation lines revealing possible temperature-time combinations for a targeted inactivation were calculated. The given information should serve as a base to deduce individual parameters (e.g., time and temperature) for handling each dairy derived enzyme.