Reversible cold gelation of sodium caseinate solutions with added salt

During a study on the effect of addition of monovalent and divalent salts on the apparent viscosity of sodium caseinate solutions (Carr et al. 2002) it was discovered that many of the high viscosity solutions appeared to gel when refrigerated. Furthermore this cold gelation was found to reverse on heating. The phenomenon of reversible cold gelation of caseinate solutions has not been reported. The most well known example of reversible cold gelation is gelatin solutions, but a number of polysaccharides also form gels on cooling, e.g. agarose, pectin and carrageenan (Evans & Wennerstrom, 1994). Whey proteins also gel at 25 (degree)C in the presence of calcium ions, though not in their absence, and this gelation is not reversible (Barbut & Foegeding, 1993).