MILK PROTEIN-CARRAGEENAN INTERACTIONS

Factorial experimental designs were employed to study the major factor s governing the gelation of milk/kappa-carrageenan mixtures. The relat ive effects of carrageenan concentration, pH, ionic strength, casein p roteins, whey proteins and kappa-casein genotype on the mechanical pro perties of the gels were studied using dynamic rheological techniques. Gel transition temperature was governed mainly by ionic strength and carrageenan concentration whilst gel strength was influenced by carrag eenan concentration and pH. It was found that the relative importance of the milk proteins to gelation varied with carrageenan concentration . It appeared that at high levels of kappa-carrageenan (i. e. 0.1% w/w ) gelation was predominately the result of association of kappa-carrag eenan helices to produce self-supporting gels. Milk proteins appeared to have little effect at high levels of carrageenan. However, milk pro teins interfered with gel formation at carrageenan concentrations lowe r than 0.018% w/w, thus increasing the amount of micellar casein by tw ofold inhibited gelation. Serum proteins also suppressed gelation, alb eit at lower kappa-carrageenan concentrations. These results suggested that, in the presence of milk proteins, gel formation involved mainly carrageenan-carrageenan cross-linkages and not carrageenan-casein or casein-casein linkages. Nevertheless, the possibility of a strong inte raction between kappa-carrageenan and kappa-casein on the micelles whi ch has to be satisfied first, leaving insufficient carrageenan to prov ide network forming capability, cannot be ruled out.