2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Waxy maize (native and hydroxypropylated) and potato starches were impregnated with ionic gums (sodium alginate, CMC, and xanthan, 1% based on starch solids), and heat-treated in dry state for 2 or 4 h at 130°C, and effects of heating on the paste viscosity (RVA) and clarity (light transmittance) were examined. Such treatment with sodium alginate and CMC raised the paste viscosity of native and modified waxy maize starches, but decreased that of potato starch. Xanthan provided the most substantial changes in paste viscosity among the tested gums. It heavily restricted the granular swelling of native and modified waxy maize starches, but increased swelling of potato starch. The final viscosity at 50°C was raised in all the starches, approximately by 500 - 1,000 cp, by this treatment. Paste clarity was also different between waxy maize and potato starches. The paste of waxy maize starch-gum mixtures became opaque and shorter textured by the heat treatment, regardless of the gum type, whereas the potato starch did not show any obvious change. It is hypothesized that the ionic gums behaved as cross-linking agents as well as forming graft copolymers through the heat-induced ester formation. Due to the presence of like charges, potato starch was less reactive than waxy maize starch. This simple heating process with ionic gums could be used as a potential physical modification method for starch.