Functional and thermal properties of wheat, barley, and soy flours and their blends treated with a microbial transglutaminase

The effects of transglutaminase (TG) on the functional and thermal properties of wheat, barley, and soy flours and their blends were investigated. Free amino and thiol groups and aromatic hydrophobicity in samples were decreased with TG treatment (P < 0.05), confirming the polymerization of proteins in flours by TG treatment. TG-treated samples had increased water-holding capacity, fat adsorption, and emulsion stability, and slightly decreased emulsion activity. The addition of barley or soy to wheat flours decreased fat adsorption and emulsion stability, but these values increased, upon TG treatment of the same blended samples, to levels as high as for untreated wheat alone. TG treatment did not significantly affect the transition peak temperature of the flour samples. However, TG treatment lowered the transition enthalpy of wheat blended with barley or soy flour, and, conversely, increased that of wheat flour samples alone. Results suggest that protein cross-linking by TG can produce unique and improved functionality even in wheat blended with barley or soy flour, and could provide opportunities for exploitation of this enzyme for product development.