MODIFICATIONS IN DISULFIDE REACTIVITY OF MILK INDUCED BY DIFFERENT PASTEURIZATION CONDITIONS

The effect df pasteurization and repasteurization on disulfide chemica l reactivity of milk proteins was tested after proteolytic digestion. Pasteurization at 75 degrees C, but not at 80 degrees C or repasteuriz ation, resulted in a decrease in disulfide reactivity compared with ra w milk. No differences among heated milks were observed in in vitro pr otein digestibility, electrophoretic behavior or surface hydrophobicit y. Whey proteins extracted from milk pasteurized at 75 and 80 degrees C had lower solubility, protein digestibility, disulfide reactivity an d surface hydrophobicity than those extracted from raw milks. SDS-PAGE and surface hydrophobicity parameters (K-d, F-max) of whey proteins s uggested that differences in disulfide reactivity were a consequence o f disulfide-mediated selective aggregation of the whey proteins.