COMBINED EFFECTS OF TEMPERATURE AND HIGH-PRESSURE TREATMENTS ON PHYSICOCHEMICAL CHARACTERISTICS OF SKIM MILK

The combined effects of temperature (4, 20 and 40 degrees C) and high- pressure treatments (250, 450 and 600 MPa for 30 min) on the physicoch emical characteristics of skim milk were studied. At 4, 20 and 40 degr ees C, the effects of high-pressure treatments were similar (except fo r the treatment at 250 MPa), leading to an increase in protein hydroph obicity, a decrease in lightness, a decrease in average diameter of pa rticles and slight solubilization of calcium and phosphorus from the c olloidal to the aqueous phase of the milk. At the same time, denaturat ion of p-lactoglobulin probably occurred. At 40 degrees C, and especia lly at 250 MPa, the effects were very different because protein hydrop hobicity remained unchanged and the average diameter of particles incr eased with the presence of two distinct populations of casein micelles . These results are discussed in relation to the effect of high-pressu re treatments on protein structure. (C) 1997 Elsevier Science Ltd.