Thermal properties of whey protein aggregates

Aggregation of 10% whey protein solution was induced by addition of calcium salt, acidification, or proteolysis at 45 degrees C. Effects of the preagg regation on thermal properties of whey proteins were examined by differenti al scanning calorimetry. The different types of aggregates had three common effects: I) one endothermic peak, representing denaturation of whey protei n aggregates, instead of two endothermic peaks representing alpha- lactalbu min and beta-lactoglobulin in the control; 2) a narrower range (similar to 10 degrees C) of denaturation temperature than the control (similar to 20 d egrees C); and 3) significantly greater enthalpy values (similar to 4 J/g) than the control (<2 J/g). Denaturation temperatures (TD, To) of the aggreg ates were also different from those of alpha-lactalbumin (67 degrees C) and beta-lactoglobulin (76 degrees C) of the control. Aggregates induced by ca lcium salt (similar to 74 degrees C) and protease (similar to 73 degrees C) had intermediate denaturation temperatures. The pK-induced aggregates had high denaturation temperatures (80 to 91 degrees C) at low pH (3.5 to 5.7). An exothermic peak was detected during calcium salt- or protease-induced a ggregation of whey proteins at 45 degrees C. Thus, the preaggregation chang ed thermal properties of whey proteins. This information on thermal propert ies of the aggregates may help in the design of appropriate heat processing for the application and manufacture of whey protein products.