Solubility of protein fibers obtained from casein solutions and liquid two-phase water-casein-sodium alginate systems

The solubility of protein and protein-polysaccharide matrix fibers obtained from casein solutions and two-phase water-casein-sodium alginate (W-C-A) systems in water and in 1 M NaCl solutions at different pH at 20 and 100 degrees C has been studied. The matrix fibers obtained from the two-phase W-C-A system are shown to be considerably less soluble than those from the casein solutions. This difference is seen particularly clearly when pH amounts to 5-7. However, it disappears with the spinning two-phase system at temperature above 80 degrees C. An assumption has been made about the matrix fibers being either mixed gels of the thermo-reversible, soluble calcium caseinate and thermo-irreversible insoluble calcium alginate, or complex protein-polysaccharide gels formed with the participation of the calcium ions. This latter assumption is in conformity with the negligible solubility of the protein fibers obtained as a result of the lyotropic gelation of the skimmed milk proteins.