EFFECT OF HEATING AND COOLING ON THE GELATION KINETICS OF 7S GLOBULIN FROM SOYBEANS

The gelation process of 15% (w/v) 7S globulin was studied using dynamic viscoelastic measurements when temperature was kept at 80 degrees C for 30 min and lowered to 20 degrees C. In the presence of I M NaSCN, the increase in the storage modulus G' was inhibited in the heating process. With increasing concentration of NaCl, the increase in the storage modulus G' was inhibited. The gel was not formed in the presence of more than 4 M guanidine hydrochloride. When the heat-induced gel of 7S globulin was again heated from 20 to 80 degrees C, the storage modulus G' decreased, showing that the gel formation in the cooling process is thermally reversible. Difference infrared spectra also indicated that the band at 1618 cm(-1) (associated with beta-sheet structure) of 7S globulin gel was decreased with increasing temperature. These results suggest that hydrophobic interactions and hydrogen bonds are very important for the formation of 7S globulin gel.