Thermal denaturation of whey proteins: effect of pH and milk sugars

ABSTRACT

Influence of pH and milk sugars on thermal stability of whey proteins were studied using heat-induced precipitation and differential scanning calorimetry Heating whey at 90°C for 10 min above pH 3.7 to 3.9 produced extensive protein denaturation. When the same heat treatment was applied below pH 3.7 protein precipitation was greatly reduced; however, protein denaturation still occurred in various whey protein fractions. Presence of milk sugars [lactose, glucose, and galactose] appeared to increase the thermal stability of beta-lacto globulin. Heat stability of alpha-lactalbumin was less at pH 3.5 than in the pH 6.5 to 4.5 range; at all pH denaturation temperatures of alpha-lactalbumin [61.6 to 57.6C] were lower than those for beta-lacto globulin or serum albumin