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Proteolysis in Ultra-High-Temperature Treated and Canned Ten Percent Cream

Industrial Laboratories of Canada, Tillsonburg, Ontario, Canada

ABSTRACT

Proteolysis in ultra-high-temperature treated (137 C for 8 s) and aseptically canned 10% cream was studied to assess its role in coagulation of sterile cream during storage. Cream was mixed with hemoglobin in borate buffer, pH 8.6, as the substrate and was incubated for 16 to 30 wk at 32 ± 1 C. Proteolysis in unsterilized 10% cream was evident by increases in optical density of trichloroacetic acid filtrates of mixtures of cream and hemoglobin during incubation. Optical densities of filtrates from two batches of cream and hemoglobin were essentially the same for 16 wk of incubation. There was no increase in nonprotein nitrogen in sterile cream incubated at 23 ± 2 C for 16 wk. However, nonprotein nitrogen in cream increased during storage at 32 ± 1 C; this was attributed to heat-induced proteolysis. Native milk proteolytic enzymes were destroyed during processing of 10% cream by ultra-high-temperature treatment.