Multiple length scale structure-property relationships of wheat starch oxidized by sodium hypochlorite or hydrogen peroxide
Madan Kumar Chapagai, Brenton Fletcher, Torsten Witt, Sushil Dhital, Bernadine M. Flanagan, Michael J. Gidley
Abstract
Wheat is a potential source of oxidized starch, but there is no systematic study reporting the effects of oxidation conditions on the structural changes and subsequent physical properties. We report the properties of oxidized wheat starch granules treated with 2, 5, and 10% hydrogen peroxide (at pH 4 and 10) or sodium hypochlorite (at pH 4, 7, and 10). Increasing concentrations favored the formation of carbonyl groups by H2O2 and carboxyl groups by NaOCl. Granule morphology and molecular order were little affected, but increasing oxidant concentration reduced polymer size. Both oxidants influenced temperatures of gelatinization and caused major reductions in pasting viscosities. Principal component analysis (PCA) suggested that both functional group content and depolymerization contributed to the variations in gelatinization, pasting, and solubility properties. Controlled oxidation of wheat starch by H2O2 or NaOCl can produce oxidized starches of different functional properties useful in diverse potential applications.