A study of the heat stabilities of a number of indigenous milk enzymes

Summary

Heat stability profiles of a number of indigenous bovine milk enzymes were examined with the object of being able to monitor heat treatments slightly more severe than typical pasteurization conditions by measurements of residual enzyme activity after heating. Assay procedures were limited to simple fluorimetric, or preferably colorimetric, methods that would be most likely to form the basis of a quick, simple and inexpensive test. Both lipoprotein lipase and α-fucosidase were relatively sensitive to heat and were totally inactivated at temperature/time combinations below those of pasteurization, but the latter may be satisfactory for studying temperatures in the range 55–65°C. Rather more heat stable were N-acetyl-β-glucosaminidase and γ-glutamyl transpeptidase, which may be most appropriate for 65–75°C and 70–80°C respectively. Higher temperature treatments between 80 and 90°C could best be investigated by following α-mannosidase or xanthine oxidase activity.