Studies of Lipase Action

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Abstract
Six series of samples were prepared on six successive days. In each case, the milk was obtained in the morning from the same group of eleven cows which were known to produce milk high in lipase activity. The mixed milk was separated, without cooling, at 91 ° F. (33 ° C.) to yield a cream contain- ing 20 per cent of fat. This cream was heated in a water bath to a predeter- mined temperature (different on each day) and portions were removed after various periods of holding. These portions were stored in ice water for twenty-four hours, and then churned at 58 ° F. (14 ° C.) in a battery of motor driven churns immersed in a constant temperature bath. The butter samples were washed and stored unsalted, in sterile jars. Samples were removed periodically for the determination of free fatty acids. At the end of 58 weeks, the experiment was concluded and Professor E. S. Guthrie was asked to score the: butter samples. The storage temperature was not uniform during the entire period. During the first six weeks and the last eighteen weeks, the butters were held at 0 ° to 8 ° F. During the remainder of the period they were held at 28 ° to 32 ° F. DISCUSSION Figures 1 to 4 show the progress of lipolysis in these samples. The data for the higher temperatures, 170 ° F. (77 ° C.) and 180 ° F. (82 ° C.), are omitted because no appreciable lipolysis occurred in any of the samples heated to these temperatures. The slight increase (about 0.2 acid degrees) observed in all of the highly heated samples is possibly due to the normal hydrolysis of fat in contact with water, even in the absence of an enzyme.

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