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

Abstract

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 °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 °C. An assumption has been made about the matrix fibers being either mixed gels of the thermoreversible, 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.