THE EFFECTS OF HIGH-PRESSURE ON WHEY-PROTEIN DENATURATION AND CHEESE-MAKING PROPERTIES OF RAW-MILK

The effects of high pressure, from 100 to 400 MPa (14,500 to 58,000 ps i) and applied for different periods (10 to 60 min), on the biochemica l and microbiological characteristics of milk have been investigated. Particular attention was paid to modifications of the cheese-making pr operties. High pressure slightly improved the microbiological quality of milk without modifying the activity of native milk enzymes such as lactoperoxidase or plasmin. beta-lactoglobulin was denatured by pressu res >100 MPa, but alpha-lactalbumin and bovine serum albumin were resi stant to pressures less than or equal to 400 MPa for 60 min. Cheese yi eld, as estimated by centrifugation of curd, increased with pressuriza tion at 300 and 400 MPa, reflecting incorporation of additional beta-l actoglobulin and, especially, greater moisture retention. The coagulat ion time decreased as pressure increased less than or equal to 200 MPa and then increased again until at 400 MPa, reaching values comparable with those of the raw milk. High pressure treatment of milk can be an effective method for improving the coagulation characteristics of mil k and for increasing the moisture retention of fresh cheese with a min imum of modification of other properties important for cheese making.