Functional properties of soy protein fractions produced using a pilot plant-scale process

Soy proteins fractionated by the modified Nagano process (Nagano method) and a simplified pilot-plant process (CCUR method) were studied for their functional properties, including solubility, viscosity, emulsification, and foaming. The functional properties of the three fractions produced by the Nagano method-glycinin (11S), P-conglycinin (7S), and an intermediate fraction (IM)-were studied under a selected range of pH, ionic strengths, and protein concentrations. The 11S fraction was more soluble than the 7S at pH 2-3, whereas the 7S was more soluble than 11S at pH 5-6. Adding NaCl changed the solubility of both fractions at pH 4-5 compared to a neutral pH. Other functional properties were related to solubility in the 7S and 11 S fractions. The CCUR method yielded only two fractions, 11S and 7S, and the functionality of those fractions was tested at a neutral pH. The solubility of the CCUR samples was slightly higher at extreme pH levels compared to 11S and 7S fractions from the Nagano method at a neutral pH. The relationship between solubility and other functional properties was clearer in CCUR samples. These results indicate that the simplified pilot-scale CCUR fractionation process can influence the functional properties of the protein fractions.