Simplified process for soybean glycinin and beta-conglycinin fractionation

A simplification of the pilot-plant scale modified Nagano method yielding t wo protein fractions, glycinin and beta-conglycinin, by pH adjustment and u ltrafiltration membrane separation was developed and compared with our pilo t-plant-scale modified Nagano procedure and with a soy protein isolate pilo t-plant procedure as our reference process. Two protein fractions, glycinin and beta-conglycinin, were produced from our simplified process and compar ed to the three protein fractions, glycinin, beta-conglycinin, and an inter mediate protein mixture, produced with the modified Nagano method. The pilo t-plant yields of glycinin, beta-conglycinin, and intermediate mixture frac tions from the modified Nagano method were 9.4, 10.3, and 4.8% [dry basis ( db)], respectively. The yield of glycinin fraction of the simplified method was 9.7% (db), and it had a protein content and purity similar to those ob tained with the modified Nagano method. The yield of the beta-conglycinin f raction was 19.6% (db), which was twice that of the modified Nagano process . The protein content of beta-conglycinin was 91.6% (db), and the purity wa s 62.6% of the protein content, which was 9% lower in purity than the modif ied Nagano method. Process optimization of the simplified method suggested the best operating conditions for the membrane filtration system were 20-25 psi inlet pressure and 200-250 L/min ultrafiltration recirculation speeds.