Phase equilibria in water-protein-polysaccharide systems

Abstract

Phase equilibria in the ternary water-soy bean globulins-polysaccharides systems, containing various acidic and neutral polysaccharides (pectin, sodium alginate, carboxymethylcellulose, arabic gum, dextransulphate, and dextran) were studied. Phase diagrams of the systems were obtained. Effects of pH, concentration of a neutral salt and urea on the compatibility of soy bean globulins with polysaccharides in water media were studied. It has been shown that soy bean globulins could be incompatible with acidic carboxyl-containing polysaccharides in the whole studied range of pH (2–12) and NaCl concentrations (0–1 mol·l−1). Incompatibility of soy bean globulins with sulphated polysaccharides takes place only under condition of high ionic strength independently of pH of the system. Incompatibility of soy bean globulins with neutral polysaccharides at pH ≠ pI occured only at high ionic strength or in the presence of 6 M urea. The change pattern in separation bodies of the water-soy bean globulins-polysaccharide systems at pH pI and varied when passing from carboxyl-containing polysaccharides to sulphated or neutral. Under equal conditions compatibility of soy bean globulins with polysaccharides increased in the series: pectin < carboxymethylcellulose < sodium alginate < arabic gum < dextran < dextransulphate.