Effect of transglutaminase on protein electrophoretic pattern of rice, soybean, and rice-soybean blends

The interactions taking place in composite dough containing rice flour and soybean proteins (5% w/w) in the presence of transglutaminase, an enzyme with cross-linking activity, were studied using different electrophoretic analyses. The interaction between rice proteins and soybean proteins was intensified by the formation of new intermolecular covalent bonds catalyzed by transglutaminase and the indirect formation of disulfide bonds among proteins. The main protein fractions involved in those interactions were both beta-conglycinin and glycinin of soybean and the glutelins of the rice flour, although albumins and globulins were also cross-linked. The addition of soybean proteins to rice flour improves the amino acid balance and they also might play an important role on the rice dough properties because soybean proteins interact with rice proteins, yielding protein aggregates of high molecular weight.