Kappa-carrageenan interactions in systems containing casein micelles and polysaccharide stabilizers

When polysaccharide food gums are added to milk-based fluid systems, phase separation of casein micelles inevitably occurs, due to biopolymer incompatibility. κ-Carrageenan can prevent bulk phase separation, although stabilized systems are still microscopically phase-separated. The mechanism by which κ-carrageenan stabilizes casein micelles from phase separation was studied in this research. Images from field emission scanning electron microscopy suggested that κ-carrageenan adhered to the casein micelle surface. Dynamic light scattering data showed casein micelle diameter increasing linearly (r2=0.978) as κ-carrageenan concentration increased, within the concentration range of 0–0.03% (w/w) and 3.65% casein. Phase separation experiments in 13% milk solids-not-fat (3.65% casein) −0.14% locust bean gum mixed systems with κ-carrageenan in the coil state (60 °C), κ-carrageenan in the helical state, but with helix aggregation blocked (addition of NaI), λ-carrageenan, guar (all at 0.01–0.03%) and agarose (0.01–0.05%) were used to understand the conditions in which stabilization of phase separation occurred. Our work suggests that both κ-carrageenan adsorption to casein micelle surfaces and κ-carrageenan helix aggregation are required for it to be effective at preventing casein micelle macroscopic phase separation from polysaccharides.