Effect of Oxidation Level of High-Amylose Corn Starch on Its Acetylation, Molecular Structure, and Functional Properties

The objective of this study is to determine the effect of oxidation level on susceptibility to acetylation, molecular structure, and functional properties of high-amylose corn starch. High-amylose corn starch is oxidized with sodium hypochlorite (equivalent 10, 20, 30gClkg(-1) starch) and acetylated with the acetic acid anhydride. Content of carboxyl, carbonyl, and acetyl groups; molecular size distribution, XRD spectra, specific surface, and morphology are determined in starches. Water-binding capacity and solubility in water are also measured. Susceptibility of starch to the formation of stable organic radicals upon UV irradiation is detected with the EPR spectroscopy. The level of the oxidation of high-amylose starch has a great impact on acetylation and on changes in starch structure. It is found that acetylation increases water binding capacity and water solubility of oxidized starches. High-amylose corn starch exhibit strong susceptibility to radical formation which results from the fact that the liability of its structure is higher than that of normal and waxy ones. Modification processes prevented the destruction of starch against UV irradiation.