Sodium Bisulfite-Induced Changes in the Physicochemical, Surface and Adhesive Properties of Soy β-Conglycinin

The effects of sodium bisulfite on the electrophoresis profile; turbidity; and thermal, surface, and adhesive properties of soy beta-conglycinin protein were studied. Sodium bisulfite dissociated high-molecular-weight aggregates in the protein, and the aggregate percentage decreased with increasing sodium bisulfite concentration. Denaturation temperature of sodium-bisulfite-treated beta-conglycinin increased as sodium bisulfite increased. However, at high sodium bisulfite concentration (i.e. 36 g/L), denaturation enthalpy decreased significantly. Sodium bisulfite caused changes in the beta-conglycinin secondary structure and promoted ionization of lysine residues as indicated by FT-IR results. A sudden drop in turbidity at pH 4.8 was observed at the same salt level. The contact angle of beta-conglycinin on cherry wood reached its minimum at 6 g/L sodium bisulfite and 24 g/L on glass. Water resistance of beta-conglycinin was improved but not significantly by 6 g/L sodium bisulfite at pH 9.5. An obvious increase in adhesion strength of the protein occurred at 3 and 6 g/L sodium bisulfite at pH 4.8. A high sodium bisulfite concentration at 36 g/L sharply reduced the adhesive performance of beta-conglycinin.