Characterization of storage proteins in different soybean varieties and their relationship to tofu yield and texture

The contribution of the total soybean proteins, the storage proteins [glycinin (11S) and beta-conglycinin (7S) fractions] and their respective subunits to tofu yield and texture was studied. Protein contents were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) coupled with densitometry and reversed phase-high performance liquid chromatography (RP-HPLC), for seven soybean varieties, and correlated to tofu yield and texture. Results from SDS-PAGE, coupled with densitometry, showed that the 11S fraction proteins (r = 0.863, P<0.01), the α' polypeptide of 7S (r = 0.917, P<0.01) and the basic polypeptide of 11S (r=.0.775, P<0.01) appeared to each affect tofu yield; however, no relationship between storage protein fractions and tofu firmness was observed. On the other hand, the RP-HPLC profiles of the total soybean proteins and the 11S and 7S fractions indicated relationships between tofu firmness and the I IS fraction, the 7S fraction, and their ratio. The inverse correlation (r = -0.832, P < 0.01) between peak 7 of the 7S fraction and tofu firmness seem's to point toward. its important role in defining tofu quality. (C) 2003 Elsevier Science Ltd. All rights reserved.