Thermal properties of whey protein aggregates

Abstract

Aggregation of 10% whey protein solution was induced by addition of calcium salt, acidification, or proteolysis at 45°C. Effects of the preaggregation on thermal properties of whey proteins were examined by differential scanning calorimetry. The different types of aggregates had three common effects: 1) one endothermic peak, representing denaturation of whey protein aggregates, instead of two endothermic peaks representing α-lactalbumin and β-lactoglobulin in the control; 2) a narrower range (∼10°C) of denaturation temperature than the control (∼20°C); and 3) significantly greater enthalpy values (∼4 J/g) than the control (<2 J/g). Denaturation temperatures (TD) T0) of the aggregates were also different from those of α-lactalbumin (67°C) and β-lactoglobulin (76°C) of the control. Aggregates induced by calcium salt (∼74°C) and protease (∼73°C) had intermediate denaturation temperatures. The pH-induced aggregates had high denaturation temperatures (80 to 91°C) at low pH (3.5 to 5.7). An exothermic peak was detected during calcium salt-or protease-induced aggregation of whey proteins at 45°C. Thus, the preaggregation changed thermal properties of whey proteins. This information on thermal properties of the aggregates may help in the design of appropriate heat processing for the application and manufacture of whey protein products.