AGGREGATION INDUCED BY CALCIUM-CHLORIDE AND SUBSEQUENT THERMAL GELATION OF WHEY-PROTEIN ISOLATE

The aggregation of whey proteins that was induced by CaCl2 was investi gated by measuring turbidity and aggregate size. The effect of the agg regation on thermal gelation was determined by measuring gel hardness. Standard conditions were set at 10% whey protein solution, 20 mM CaCl 2, and 45 degrees C in order to observe the influence of different var iable levels on the aggregation. The addition of 20 mM CaCl2 to a 10% whey protein isolate solution resulted in a continuous increase in tur bidity during 5 h of incubation at room temperature (21 degrees C). As expected, an increase in temperature (21 to 45 degrees C) or CaCl2 co neentration (5 to 50 mM) increased the rate and extent of the aggregat ion. Stable colloidal aggregates were formed with 10 to 30 mM CaCl2. A n increase in protein concentration from 5 to 20% remarkably reduced t he rate and extent of the aggregation during the 5-h incubation. The a ggregation was dependent on the weight ratio of CaCl2 to whey proteins . Aggregation induced by CaCl2 before heat-induced gelation greatly af fected the hardness of the gels that were formed by heat treatment (80 degrees C for 30 min). The formation of the hardest gels required the optimal extent of aggregation or aggregate size.