Effects of Some Chemical and Physical Treatments on Proteolysis in Milk

Abstract

Addition of either a water-soluble or oil-soluble surfactant to milk enhanced proteolysis. This effect was attributed primarily to alteration in the availability of the casein and secondarily to a partial release of proteolytic enzymes from the milk fat globule membrane. Adding milk fat globule membrane to milk also increased proteolysis, presumably by contributing additional proteinase. Proteolysis increased after milk was subjected to Waring blendor treatment, ultrasonic treatment, or temperature fluctuations. These treatments presumably cause dissociation of proteinases from milk fat globule membranes or casein micelles. Addition of carrageenan to milk inhibited proteolysis. Carrageenans may inhibit proteolysis by preventing dissociation of casein micelles or by blocking access to the active sites on casein. Removing either calcium ions or colloidal phosphates from milk by dialysis enhanced proteolysis. This enhancement may be due to dissociation of casein micelles or milk proteinases originally adsorbed on the casein micelles. Removal of calcium ions increased proteolysis more than removal of colloidal phosphates. © 1986, American Dairy Science Association. All rights reserved.