Modifications in disulfide reactivity of milk induced by different pasteurization conditions

The effect of pasteurization and repasteurization on disulfide chemical reactivity of milk proteins was tested after proteolytic digestion. Pasteurization at 75°C, but not at 80°C or repasteurization, resulted in a decrease in disulfide reactivity compared with raw milk. No differences among heated milks were observed in in vitro protein digestibility, electrophoretic behavior or surface hydrophobicity. Whey proteins extracted from milk pasteurized at 75 and 80°C had lower solubility, protein digestibility, disulfide reactivity and surface hydrophobicity than those extracted from raw milks. SDS-PAGE and surface hydrophohieity parameters (K(d), F(max)) of whey proteins suggested that differences in disulfide reactivity were a consequence of disulfide-mediated selective aggregation of the whey proteins.