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The Lipase of Pseudomonas fragi¹ III. Enzyme Action in Cream and Butter

Dairy Industry Section, Iowa Agricultural Experiment Station, Ames

ABSTRACT

The presence of Pseudomonas fragi lipase in cream and, butter causes development of objectionable flavors, thus lowering the quality of these products considerably. The growth of P. fragi and the subsequent breakdown of butterfat in cream and butter has been studied by several workers, chiefly Hussong (3), Hussong et al. (4), Long and Hammer (6, 7) and Pouts (1). However, the action of the lipase, independent of the growing organisms, upon the butter-fat in cream and butter has not been studied.

The common belief is that lipases are inactivated by the pasteurization procedures to which the cream is subjected during the buttermaking process. Since the lipase produced by P. fragi is not completely inactivated by such pasteurization procedures (8), it was necessary to examine the behavior of enzyme in cream and butter under simulated commercial butter making and handling conditions.

EXPERIMENTAL PROCEDURES

The lipase test substrate for the usual measurement of lipase activity and the modified extraction-titration procedure employed with the above lipase test substrate were those reported previously (8).

¹ Journal paper No. J-2130 of the Iowa Agricultural Experiment Station, Ames. Project No. 1050.