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On the Mechanism of Activation of Lipolysis and the Stability of Lipase Systems of Normal Milk¹

Department of Dairy Industry, University of California, Davis

ABSTRACT

An understanding of the mechanism of activation of induced lipolysis in milk is essential for the effective control of rancidity. A distinction has been made between "induced" lipolysis, which involves the lipase system of normal milk, and "spontaneous" lipolysis, which occurs upon the cooling of naturally lipolytically active milk produced by certain cows (3). The activation treatments known to affect normal raw milk include homogenization, prolonged agitation of warm milk, and "temperature activation," i.e., warming precooled milk to 30° C. and cooling again to below 10° C. It has been generally considered that these treatments involve changes in the state of the substrate, making it available to lipase action.

Because of a high incidence of lipolysis on dairy farms where pipeline milkers have been adopted, a study was undertaken to obtain an understanding of the mechanism of activation of lipolysis by "air agitation." In a discussion of this problem, Herrington (1) commented: "It is difficult to understand why agitation of warm raw milk with air in a vertical pipe should produce much more activation than agitation for the same time in a Waring Blendor.

¹ This study was supported by funds from the California Dairy Industry Advisory Board.