CALCIUM-CHLORIDE, TEMPERATURE, PREHEAT TREATMENTS AND PH AFFECT THE RATE OF ACID-INDUCED AGGREGATION OF CASEIN

Increasing calcium chloride from 0 to 50 mmol/dm3 decreased the maximum rate of casein aggregation by 94% and decreased the pH from 5.2 to 4.5 at which aggregation was initiated. Increasing the temperature from 25 to 47-degrees-C, increased the maximum rate of casein association 3.4-fold and increased the highest pH at which casein micelle coalescence began from 5.1 to 5.8. The lowest pH of association (pH 3.85) was relatively unaffected by temperature. Preheating milk (70-95-degrees-C, for 7 min), accelerated the maximum rate of aggregation 1.7-fold and increased the highest pH of incipient aggregation from 5.0 to 5.4, indicating that the more intensive heat treatment of diluted skim milk increased the tendency of casein to associate.