Endogenous milk enzymes with a sufficient heat sensitivity are of particular interest for the detection of slight heat treatments of milk. The determination of alpha-fucosidase and phosphohexose-isomerase allows the characterization of a thermization, phosphodiesterase and gamma-glutamyltransferase can describe the pasteurization process, and alpha-mannosidase is an appropriate indicator for the detection of high temperature pasteurized milk. Suitable testing methods allowed the quantification of data concerning the genuine content of individual enzymes and natural deviations as well as inactivation kinetics.