Interactions between carrageenans and milk proteins: a microstructural and rheological study

Gels were produced using kappa-, iota-, or hybrid-carrageenan at a low (0.2-0.25%) and a high (0.7-1.0%) dosage in skim milk. The microstructure of carrageenan and protein was observed by confocal laser scanning microscopy using direct immunostaining. Additionally, rheology was used to characterize the gels. The low kappa- and iota-carrageenan dosages resulted in gels with a fine stranded carrageenan-protein microstructure and emulsion-like inclusions, while the high dosages resulted in strongly flocculated microstructures. Hybrid-carrageenan exhibited flocculation at both dosages. When using iota- and hybrid-carrageenan at a high dosage and kappa-carrageenan at both dosages, the gel characteristics were dominated by carrageenan-carrageenan interactions. On the other hand, the gel with a low dosage of iota-carrageenan in milk was barely fusible, indicating the presence of a true coupled network. We suggest that kappa-, iota-, and hybrid-carrageenan all interact with casein micelles but that the impact of this interaction on the total gel properties varied.