Dynamic viscoelastic properties of glycinin and β‐conglycinin gels from soybeans

Abstract

Abstract The effects of heating temperature on gel properties and conformational changes were investigated in glycinin and β‐conglycinin gels using Theological and Fourier transform ir (FTIR) methods. Solutions of 15 wt % glycinin or β‐conglycinin in 35 m M phosphate buffer at pH 7.6 were heated at various temperatures for 30 min and rheological properties were measured at 20°C. The storage modulus G ′ as a function of frequency changed from a monotonical decrease with decreasing frequency to a plateau in the range from 0.0018 to 40 Hz by heating at temperatures higher than 80°C for glycinin and 65°C for β‐conglycinin. A band at 1618 cm −1 (associated with the β‐sheet structure) on ir spectra increased with the formation of heat‐induced gels. The value of the storage modulus G ′ correlated well with the increase in absorbance at 1618 cm −1 . These results suggest that the formation of a β‐sheet structure may be closely related to the value of the storage modulus G ′ for heat‐induced gels in soybean proteins and that heat‐induced gels of glycinin and β‐conglycinin are formed by cross‐links with intermolecular β‐sheet structures. © 1994 John Wiley & Sons, Inc.