Functional properties of protein fractions obtained from commercial yellow field pea (Pisum sativum L.) seed protein isolate

Commercial pea protein isolate was separated into water-soluble (WS), salt-soluble (SS), alkaline-soluble (AS) and ethanol-soluble (ES) fractions. AS fraction was the most abundant, constituting about 87% of the proteins in PPI followed by WS, SS and ES fractions in decreasing order. ES fraction consistently formed emulsions with a narrow range of smaller oil droplet sizes (0.6–19 μm) at pH 4.0, 7.0 or 9.0 compared to a wider range of sizes for emulsions stabilised by WS, SS and AS fractions. Emulsions formed with ES fraction were also the most stable (p < 0.05) over the 3 h test period at all the pH values used in this work. The WS fraction had significantly highest (p < 0.05) protein solubility and foaming capacity at all the pH values when compared to solubility of PPI, SS, and ES. Except for AS and ES fractions, foaming capacities of the protein fractions were higher at pH 9.0 than at pH 4.0 or 7.0.