Rheology of sodium caseinate-carrageenan mixtures

The main effects and interactions of mixtures of sodium caseinate, kappa- or l-carrageenan, sodium chloride, calcium chloride and hydrogen ions on the rheological properties in aqueous systems cooled to 5C were quantified. Response surface methodology was used to display the results for five different response variables: gelation temperature, consistency index (kappa*), dynamic power law factor (n*), critical strain (gamma(c)), and syneresis. The gelation profiles observed for both kappa- and l-carrageenan systems demonstrated that the sol-gel transition in sodium caseinate-carrageenan mixtures was due to electrostatic interactions of free carrageenan loops or tails with the intewention of cations. Caseinate molecules did not play a major role in this process. The electrostatic nature of the interactions was further demonstrated by the significant influence of salts and pH on the consistency and brittleness of the gels (represented by kappa* and gamma(c), respectively). Consistency and brittleness were inversely related as well as consistency and syneresis. Syneresis was negligible in L-carrageenan gels and was reduced by sodium caseinate and sodium chloride in the kappa-carrageenan systems.