Effect of 11S/7S Ratios on Mechanical and Barrier Properties of Edible Films Based on Soybean Protein Isolate

The effect of 11S/7S ratios on mechanical and barrier properties of soybean-protein-isolate films was evaluated. The tensile strength increased with an increase of 11S globulin ratio when it was higher than 50 % in soybean-protein-isolate films, and decreased with an increase of 11S globulin ratio when it was lower than 50%. Moreover, the total soluble matter of soybean-protein-isolate films decreased with an increase of 11S globulin ratio, while the elongation at break, moisture content, and optical transparency of soybean-protein-isolate films increased with an increase of 11S globulin ratio. Furthermore, 11S/7S ratios had no influence on the water vapor permeability of soybean-protein-isolate films. These phenomenon mainly resulted from that the matrix of soybean-protein-isolate films was mainly maintained by disulfide bonds when 11S globulin ratio was higher than 50%, while that was maintained by intermolecular hydrogen bonds when 11S globulin ratio was lower than 50%.