Kappa-caffageenan 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. K-Carrageenan can prevent bulk phase separation, although stabilized systems are still microscopically phase-separated. The mechanism by which K-carrageenan stabilizes casein micelles from phase separation was studied in this research. Images from field emission scanning electron microscopy suggested that K-carrageenan adhered to the casein micelle surface. Dynamic light scattering data showed casein micelle diameter increasing linearly (r(2)=0.978) as K-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 kappa-carrageenan in the coil state (60 degreesC), kappa-carrageenan in the helical state, but with helix aggregation blocked (addition of NaI), lambda-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 kappa-carrageenan adsorption to casein micelle surfaces and kappa-carrageenan helix aggregation are required for it to be effective at preventing casein micelle macroscopic phase separation from polysaccharides. (C) 2004 Elsevier Ltd. All rights reserved.