SOL-GEL TRANSITION AND ELASTICITY OF STARCH

The concentration dependence of the mechanical properties of starch pa stes 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 elasti c modulus that characterizes the network structure. The percolation th reshold can be taken as 1.5 wt% for corn starch and as 1.0 wt% for cas sava starch. The storage modulus was scaled on C-C-c (concentration-cr itical concentration, the critical exponents being determined as 4.2 a nd 1.8 for corn starch and cassava starch, respectively. It is suggest ed from these results that the intermolecular bonding of corn starch w as rigid and that of cassava starch was flexible.