Surface functional properties of native, acid-treated, and reduced soy glycinin. 1. Foaming properties

Foaming properties of native and chemically modified glycinin were evaluate d. Effects of ionic strength and glycinin composition and concentration on foam formation and stabilization were studied. Glycinin was modified by mea ns of combined treatments: cold or hot acidic treatments, with or without l ater disulfide bridges reduction. Modified proteins obtained from glycinin present different degrees of dissociation, deamidation, and as consequence, varied surface hydrophobicity and molecular size. Parameters of forming an d stabilizing of foam were correlated with both deamidation and dissociatio n degrees of modified and native glycinin samples. A positive relationship was observed between surface behavior and foaming properties of different p rotein species. Results show that dissociation, deamidation, and reduction have produced structural changes on glycinin (increased surface hydrophobic ity, increased net charge, decreased molecular size) which enhance the adso rption and anchorage of proteins at the air-water interface and, consequent ly, improve the foam forming and stabilizing capacities.