Effect of Fenton reaction parameters on the structure and properties of oxidized wheat starch
Abstract
Wheat starch was oxidized through a Fenton reaction by hydrogen peroxide and Iron II sulfate as a catalyst at various concentrations and reaction duration. The formation of carbonyl and carboxyl groups confirmed the starch oxidation as determined with Fourier-transform infrared (FTIR) spectroscopy. The degree of oxidation was estimated by carbonyl and carboxyl titration. The various oxidized wheat starches presented considerable variations in their oxidation level as a function of the catalyst concentration and oxidative process duration. The effect of the Fenton reaction parameters on the starch macromolecular chains and microstructure was evaluated by X-ray diffraction and amylose content estimation. Significant depolymerization of the starch macromolecules was observed, mainly in the starch amorphous phase, followed by a degradation of the crystalline phase at a higher oxidation level. SEM observations revealed changes in starch structure, which ranged from minor degradation of the starch granules to a more crosslinked morphology.