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

Alginate is widely used to enhance textural properties of processed foodstuffs including starch-based products. Information on rheological properties of these mixed gels is limited. This study aims to characterize the rheological properties of alginate/starch mixed gels, and determine the effect of starch on gelation and textural properties of these model systems. Native and modified starch from cereals and roots/tubers with distinct gelling properties were utilized. Solutions (80 C) containing various levels of alginate, Ca++, and starch were subjected to dynamic oscillatory tests with changing temperature, time and frequency. The mixed gels were also subjected to compression and vane tests for rheological characterization at large strain deformation. Oscillatory shear results showed that hot mixtures of alginate/starch formed weak gels which became stronger upon cooling to 5°C and holding. For a given concentration of alginate (e.g. 0.5% w/w) and Ca++ (600 ppm), gel strength (G') increased by 2-5 times with added starch (2-10% w/w) and varied with starch type. Fracture stress and strain of the mixed gels under large deformation were not always consistent with G' values. Depending on the type and concentration, starch acts as filler in an alginate matrix or forms a co-network resulting in different fracture behavior and textural properties. Added starch significantly reduced syneresis in alginate gels. The generated information provides a baseline for development of alginate-starch systems with desired textural characteristics and storage stability.