Conformational changes and functional properties of acid-modified soy protein.

Abstract

Changes to the conformation and functional properties of soy protein caused by mild acid treatment were investigated. When a 2% soy protein solution in 0.05 N HCl was heated for 30min at 95°C, the functional properties of the protein, including its solubility, emulsifying properties and foaming properties, were greatly improved. It was found that the soy protein can be deamidated preferentially without significant cleavage of the peptide bonds under these carefully controlled conditions in dilute acid (0.05 N HCl at 95°C for 30 min). The functional properties of the soy protein were increased greatly with an increase in surface hydrophobicity at an early stage of the mild acid treatment. These results suggest that the improvement in the functional properties of acidmodified soy protein may be mainly due to an increase in surface hydrophobicity induced by deamidation and acid-induced denaturation.