Effect of calcium chelators on heat coagulation and heat-induced changes of concentrated micellar casein solutions: The role of calcium-ion activity and micellar integrity

There is general consensus that calcium chelators enhance heat stability in milk. However, they increase the heat stability to considerably different extents. For this reason, the effect of various calcium chelators on heat coagulation and heat-induced changes of concentrated micellar casein solutions was investigated by measuring the heat coagulation time (HCT), together with changes in calcium-ion activity, viscosity, turbidity, and zeta potential before and after heating. Surprisingly, the weakest chelator, disodium uridine monophosphate (Na2UMP), gave the most pronounced increase in HCT. Stronger chelators, i.e., disodium hydrogen phosphate, trisodium citrate and sodium phytate, gave a lower HCT than Na2UMP. Sodium hexametaphosphate (SHMP) was the least effective heat stabilizer. Heat-induced changes in SHMP were the major cause for this reduced heat stability effect. Differences in HCT caused by the addition of the various calcium chelators could be attributed to the calcium-ion activity and state of the micellar structure before and during heating.