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 for mulations (1-2% w/w hydrocolloid on a starch basis), polysaccharides o f varying molecular structures (xanthan, beta-glucan, arabinoxylan, gu ar gum) did not affect the gelatinization temperature of waxy maize an d wheat starches. However, the hydrocolloids increased the phase trans ition temperature range (T-m-T-i) and the melting enthalpy of starch c rystallites, implying a stabilization of the granular structures durin g heating. There was also an enhancement in the crystallization rate o f amylopectin on aging gels at 5 degrees C, the effect being more mark ed with the waxy maize starch gels. The most pronounced effect, howeve r, 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 o f intermolecular associations among amylopectin molecules by the polys accharide, which seems to be a prerequisite for establishment of a con tinuous network structure. In contrast, wheat starch gel rheology did not seem to be affected by the hydrocolloids.