| 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. |
