Factors affecting the acid gelation of sodium caseinate

Acid gelation, turbidity and particle size development of dispersions of sodium caseinate and other protein fractions were studied. Sodium casemate dispersions became particulate prior to the onset of gelation. Casein particles had enhanced stability to gelation in the presence of sodium chloride. Removal of the hydrophilic part of the kappa-casein molecule through renneting and acidification of the soluble sodium para-caseinate resulted in increased gelation pH. Removal of most of the kappa-casein through ethanol fractionation of sodium caseinate resulted in an alpha(sl)-beta-fraction, which was markedly destabilised at higher pH values during acidification in the presence of sodium chloride. Preheated beta-lactoglobulin/sodium caseinate dispersions had similar acid gelation profiles in the presence of sodium chloride with or without N-ethylmaleimide, suggesting that secondary thiol-disulphide interchange reactions between kappa-casein and preheated beta-lactoglobulin aggregates did not effect the gel point and final storage modulus in the short time-frame (120 min) of acidification. It was found that kappa-casein and sodium chloride played a significant role in both particle development and subsequent stability of sodium caseinate dispersions on acidification. (c) 2005 Elsevier Ltd. All rights reserved.