The proteolytic activity in three commercial ultra-pasteurized, aseptically packaged samples of cream that developed bitter flavor was studied. Samples were analyzed for microorganisms and rate of proteolysis as affected by reaction temperature and pH. The temperature effect was determined at 20, 30, 37, 45, and 50 C. Samples A and B had an optimum temperature of 37 C for proteolytic activity while Sample C had its optimum between 30 and 37 C. Sample B had increased activity at pH 7.0, 8.0 and 9.0. Sample A had increased activity between pH 7.0 and 7.5 while Sample C exhibited greatest activity at pH 8.0. The rate of proteolysis increased with incubation time.

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Author notes

1Fla. Agricultural Experiment Station Journal Series No. 1109.

2Present address: Department of Animal Science, Texas A&M University, College Station, TX 77843.