Reversibility of NaCl-induced changes in physicochemical properties of bovine milk

NaCl-induced changes in physicochemical properties of milk are widely reported but no information is available at present about the reversibility of such changes. In this study, the reversibility of NaCl-induced changes in the heat stability, ethanol stability, rennet coagulation time and the concentration of ionic calcium were examined. NaCl-induced reductions in the stability of milk against heat- and ethanol-induced coagulation and increases in the stability against rennet-induced coagulation were largely reversible on removal of excess NaCl by exhaustive dialysis against bulk milk. Some minor changes remained, which could be attributed to the lower level of ionic calcium in milk from which added NaCl was removed by dialysis than in control milk. The results of this study suggest that addition of NaCl has no irreversible effect on the physicochemical properties of casein micelles, but some changes in the mineral balance remained.