A comparison of native and acid thinned normal and waxy corn starches: Physicochemical, thermal, morphological and pasting properties

The starches isolated from normal and waxy corn varieties were hydrolyzed with hydrochloric acid (0.14mol equivalent/L) and evaluated for physicochemical and functional properties. Acid thinning decreased the amylose content and swelling power but increased the solubility. The light transmittance of acid thinned (AT) starch pastes was higher than those of their native starches after similar storage intervals. The scanning electron microscopic observation demonstrated that the acid thinning did not cause any disruption of the granular crystalline Structure. Native normal corn starches showed lower onset temperature (T-O) and peak temperature (T-p) as compared to their counterpart AT starches, whereas the reverse was observed for waxy corn starch. Entlialpy of gelatinization (Delta H-gel) was lower ill AT normal and waxy starches as compared to their native starches. The percentage of retrogradation (%R) was significantly higher for native corn starches as compared to their AT starches. A significant reduction in peak-(P-v), trougll-(T-v), breakdown-(B-v) final-(F-v). and setback viscosity (S-v) was observed by acid thinning, and the reduction was more pronounced in AT waxy starches. Among AT starches, AT waxy starch showed the lowest values of P-v, T-v, B-v, F-v, and S-v. (c) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.