Modification of starch by dry heating with ionic gums

Waxy maize (native and hydroxypropylated [HP]) and potato starches were impregnated with ionic gums (sodium alginate, CMC, and xanthan, 1% based on starch solids) and heat-treated in a dry state for 0, 2, or 4 hr at 130°C. Effects of the dry heating on paste viscosity (RVA) and clarity (light transmittance) were examined. Heat treatment with sodium alginate and CMC raised the paste viscosities of native and HP waxy maize starches, but decreased that of potato starch. Xanthan provided the most substantial changes in paste viscosity among the tested gums. It appeared to heavily restrict granule swelling of the waxy maize starches, but it increased swelling of potato starch granules. Dry heating raised the paste viscosity of all the starch-gum mixtures tested, except the potato starch-alginate mixture. The final viscosity at 50°C of a 7% paste was raised in all other starches by ≈500-1,000 cP by this treatment. The paste of waxy maize starch-gum products became opaque and shorter textured by the heat treatment, regardless of the gum type, whereas potato starch-gum products did not show any obvious change in paste clarity. Ionic gums could behave as cross-linking agents as well as form graft copolymers through heat-induced ester formation. This simple heating process with ionic gums could be used as a modification method for starch.