COMPARISON OF THE EFFECTS OF HIGH-PRESSURE TREATMENTS AND HEAT PASTEURIZATION ON THE WHEY PROTEINS IN GOATS MILK

Goat's milk was subjected to pressures up to 500 MPa at 25 or 50 degre es C, and the extent of denaturation of the individual whey proteins, determined from their loss of solubility at pH 4.6, was examined by ge l permeation FPLC (fast protein liquid chromatography) and SDS-PAGE. O n pressure treatment at 25 degrees C, beta-lactoglobulin readily aggre gated, whereas the immunoglobulins and alpha-lactalbumin were more res istant. At 50 degrees C, the effect was greater, and the immunoglobuli ns and alpha-lactalbumin were also partially denatured. SDS-PAGE showe d that after pressure treatment the proteins in the acid precipitate w ere disulfide linked. Some small soluble aggregates of beta-lactoglobu lin remained in the acid whey from pressurized milk, and these were no t present in acid whey from heat-treated milk. Thermal and pressure tr eatments of milk could be distinguished by their different effects on denaturation of the individual whey proteins. Also, the activity of al kaline phosphatase in goat's milk was reduced by pasteurization but no t by high-pressure treatment up to 500 MPa for 10 min. The possible us e of these differences for monitoring thermal and pressure treatments in milk, and the importance of high pressure treatment in denaturation of the whey proteins, are discussed.