Effect of soy protein subunit composition on tofu quality

Tofu was made, using two coagulants, from soybean lines which lacked specific glycinin and β-conglycinin protein subunits and the quality evaluated to determine the effects of specific protein subunits. The group IIb (A3) glycinin subunit played the major role in contributing to tofu firmness, regardless of coagulant, while the group IIa (A4) subunit had a negative effect on tofu quality in 2002. Soybeans with the group I (A1A2) subunit resulted in tofu with textural properties about one-third higher, expressed as a percent of Harovinton’s values, than tofu prepared from soybeans without the group I subunit. The individual components of group I had contradictory effects on GDL tofu quality in 2002, with the A1 subunit having a negative effect and A2 having a major positive effect. Lack of the α′ subunit of β-conglycinin increased gel hardness relative to the complete 7S protein.