Changes in Functional Properties by Transglutaminase Cross Linking as a Function of pH of Legumes Protein Isolate

Abstract

The effect of cross linking of the protein isolates of pigeon pea and hyacinth bean with the microbial transglutaminase (EC 2.3.2.13) on the functional properties at different pH levels was studied. The protein isolate of each legume was dissolved at concentration of 10 mg mL^-1 in 0.1 M phosphate buffer, pH 7.5, and then reacted with transglutaminase (0.5 mg mL^-1). Then, free amino group, solubility, heat stability, and emulsifying and foaming properties of the transglutaminase treated protein isolate were investigated. The reduction in the total free amino groups (OD340) of the polymerized protein showed that transglutaminase treatment cross-linking the protein subunit of each legume. The solubility of the protein polymer of each legume was greatly improved at a wide range of pH level. Cross linked proteins were less turbid on heating to higher temperature as compared to untreated samples and the temperature at which the protein turns turbid also increased in the polymerized samples. The emulsifying and foaming properties of the protein polymers were greatly improved at a wide range of pH level compared to the flour and the native protein of the two legumes.