Functional Properties Modulation of Soybean, Adzuki Bean, Mung Bean, and Peanut Proteins Through Alkaline Extraction...

This study investigates the effects of alkaline extraction pH on the yield, composition, structure, and functional properties of proteins from soybeans, adzuki beans, mung beans, and peanuts. Protein extraction at highly alkaline conditions (pH 12) increased protein yield by 10.88% in adzuki beans and by 11.65% in mung beans but resulted in remarkably darker coloration. The highly alkaline conditions decreased the particle size of the soybean proteins by 23.96% and adzuki bean proteins by 23.2%, and altered the amino acid compositions of adzuki bean proteins. Depending on the extraction conditions, differences were observed in the secondary and tertiary structures as well as in the subunit composition of proteins, and these effects were distinct among the different legumes. The functional properties were notably affected, with protein solubility indices decreasing by 10.34% at high pH. Moreover, the water solubility index showed a remarkable decrease in adzuki and mung beans by 64.29% and 43.80%, respectively. The foaming capacity was higher for proteins extracted at pH 12, suggesting their suitability for applications requiring a soft and voluminous texture, whereas the emulsifying activity was higher at pH 9, which suggests suitability for emulsified products. Thus, adjusting the extraction pH may effectively modulate the functionality of legume proteins for food applications.