Dynamic Viscoelastic Study on the Gelation Properties of β-Conglycinin-Rich and Glycinin-Rich Soybean Protein Isolates

Preheated soybean protein isolates (SPIs) were prepared from new soybean lines that have extremely different compositions of β-conglycinin and glycinin by a typical method for manufacturing commercial SPI. The gelation properties of these SPIs were investigated by dynamic viscoelastic measurements. The storage modulus G‘ of 12% SPI was measured at pH 7.0 when the temperature was increased from 30 to 80 °C and then lowered to 20 °C at 2 °C/min. Gelation properties of the preheated SPI were different from those of the non-pre-heated SPI. In the absence of NaCl, an increase in the storage modulus G‘ was observed for preheated β-conglycinin-rich SPI and preheated control SPI, but not for preheated glycinin-rich SPI. On the other hand, in the presence of 2.5% NaCl, an increase in the storage modulus G‘ was observed for all preheated SPIs in the order β-conglycinin-rich SPI > control SPI > glycinin-rich SPI. These results suggest that β-conglycinin plays an important role in the heat-induced gel formation of commercial SPI.