Contribution of 11S and 7S Globulins of Soybean Protein to the Formation and Properties of Yuba-film

Abstract

To elucidate the functional properties of Yuba-film formed from 11S and 7S globulins of soybean protein, Yuba-like films were prepared from the solution of CIF (11S) and crude 7S glubulin (7S), and the conditions of film formation, stress, strain and other properties of the films were studied.
The films from 11S were always stronger than those from 7S. Their stress and strain values varied with the changes of pH value of the solution, but in neutral range-normal condition of Yuba production, it was considered that 11S contributed to the strength of the film and 7s mainly to the hardness or brittleness.
Adding 2-mercaptoethanol, N-ethylmaleimide or urea in the protein solution, formed films decreased the strength remarkably. It was seemed that SH_??_SS reaction was concerned in the strength of films. Wrinkles peculiar to Yuba-film might have something to do with SS-linkage in the film proteins, because they appeared on 7S film, but not on 11S film, and they did also on the latter when it was prepared adding N-ethylmaleimide.