Effect of 7S/11S ratio on the network structure of heat-induced soy protein gels: a study of probe release

Abstract

The release behavior of poly(ethylene glycol) (PEG) with different molecular weights (M_w): 6000, 20 000, 100 000 and 400 000 g mol⁻¹ from heat-induced soy protein gels as a function of the 7S/11S protein ratio was investigated. Results showed that time-related release of PEG from gel network fit the Fick's second law. PEG diffusion coefficients depended on the PEG size and gel network structure, which increased with increasing 11S ratio in gel or decreasing probe molecular weight. Moreover, the diffusion of PEG with higher molecular weight was more sensitive to the variations of gel internal network. The changes of PEG diffusion coefficients in soy protein gel were consistent with the variations of gel structure characterized by scanning electron microscopy (SEM). Gels formed at lower 11S ratio were composed of homogeneous spherical aggregates structure, while gels formed at higher 11S ratio showed higher extent of macro-phase separation and coarser network with larger pores.