Moderate Vinyl Acetate Acetylation Improves the Pasting Properties of Oxidized Corn Starch

Abstract

AbstractIt is generally believed that acetylation can enhance the hydrophilicity of starch, resulting in increased viscosity. However, moderate vinyl acetate acetylation is interestingly found to decrease the peak viscosity of oxidized starch during pasting in this study. This low viscosity of starch paste is extremely desirable in paper surface sizing and textile sizing. Corn starches are oxidized by NaClO (4.0% chlorine) and then acetylated using vinyl acetate at different levels. The peak viscosity of oxidized starch modified by vinyl acetate is reduced by 67.1%. Fourier transform infrared spectroscopy confirms the presence of acetyl groups with a peak at 1730 cm−1. X‐ray diffraction analysis shows that the intensity of crystalline peaks of oxidized–acetylated starches is decreased compared with that of oxidized or acetylated starch. Granule morphology observations further reveal extensive surface damage of the granules resulting from moderate acetylation. Molecular size distribution analysis also shows that the moderate vinyl acetylation can significantly reduce (≈60%) the average molecular weight of oxidized starch. These results show that moderate acetylation can change the structural and morphological properties of oxidized starch, leading to a considerable drop in paste viscosity and shows great application potential in the starch industry.