Effect of High-Temperature Short-Time Heat Treatments on Some Properties of Milk. II. Inactivation of the Lipase Enzyme

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Abstract
The holding times at various temps. from 145-185 F required to prevent lipolysis induced by homogenization of raw milk were detd. temp. with time studies show a semi-log relationship. At 145 F, approx. 1/3 the time was required to inactivate the lipase as was required to inactivate the phosphatase; at 185 F the same time was required to inactivate both enzymes. Addition of Cu under the conditions of these expts. had no noticeable effect on the time-temp. relationships for inactivation of lipase. Instantaneous exposure at 142 F was sufficient to inactivate the enzyme when milk was tested at the rate of 5 F per min. Heating by means of the Mallory unit within 5 sec. required a temp. of 185 F with instantaneous exposure. The time required at any temp. to inactivate the lipase was found to vary with the rate of heating to and cooling from the holding temp.