Effect of hydrocolloids on gelatinization and structure formation in concentrated waxy maize and wheat starch gels

Starch-hydrocolloid interactions were studied in concentrated (40% w/w starch) aqueous dispersions by differential scanning calorimetry and dynamic rheometry. At the levels commonly employed in food product formulations (1-2% w/w hydrocolloid on a starch basis), polysaccharides of varying molecular structures (xanthan, beta-glucan, arabinoxylan, guar gum) did not affect the gelatinization temperature of waxy maize and wheat starches. However, the hydrocolloids increased the phase transition temperature range (T-m-T-i) and the melting enthalpy of starch crystallites, implying a stabilization of the granular structures during heating. There was also an enhancement in the crystallization rate of amylopectin on aging gels at 5 degrees C, the effect being more marked with the waxy maize starch gels. The most pronounced effect, however, has been the retardation of gelation kinetics of waxy maize starch by the hydrocolloids. The decrease in storage modulus (G') development of amylopectin-hydrocolloid gels was attributed to the interference of intermolecular associations among amylopectin molecules by the polysaccharide, which seems to be a prerequisite for establishment of a continuous network structure. In contrast, wheat starch gel rheology did not seem to be affected by the hydrocolloids.