New food ingredient derived from casein/kappa-carrageenan interaction
This thesis is an investigation of a novel method to form casein/[kappa]-carrageenan aggregates in skim milk, by mixing solutions of each at 60°C and cooling to 25°C while shearing. The average particle size of casein/[kappa]-carrageenan aggregates decreased with increasing shear rate (200, 400 and 800 s -1) but increased with [kappa]-canageenan concentration (0.025% 0.05% and 0.075%). Oscillatory rheology measurements demonstrated that skim milk containing 0.025% [kappa]-carrageenan behaved as a dilute solution, while skim milk with 0.05% or 0.075% [kappa]-carrageenan formed weak gels, although solutions remained fluid and had a much lower moduli compared to similar solutions cooled with no shearing. The aggregates were quite stable to shear once formed. The interactions between casein micelles and [kappa]-canrageenan decreased with increasing amount of milk solids. The initial mixing temperature of reconstituted skim milk and [kappa]-carrageenan dispersions greatly affected the particle size distribution of the aggregates. Microstructural observations as well as studies in the presence of NaI demonstrated that at particular protein/polysaccharide ratios, casein/[kappa]-canageenan aggregates formed in reconstituted skim milk via adsorption of [kappa]-canageenan with casein micelles. The aggregates that formed may have synergistic functionality compared to the individual components, therefore, could be used as a new value-added ingredient in the food industry.