Sol—Gel Transition and Elasticity of Starch

Abstract

The concentration dependence of the mechanical properties of starch pastes near the sol-gel transition point was analyzed by the scaling law derived from percolation theory. Since the storage modulus curves for a starch paste slowly decrease with decreasing frequency, the plateau region at a frequency of 10-1 S -1 is shown to represent the elastic modulus that characterizes the network structure. The percolation threshold can be taken as 1.5 wt% for corn starch and as 1.0 wt% for cassava starch. The storage modulus was scaled on C-C c (concentration-critical concentration, the critical exponents being determined as 4.2 and 1.8 for corn starch and cassava starch, respectively. It is suggested from these results that the intermolecular bonding of corn starch was rigid and that of cassava starch was flexible.