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

Abstract

It 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.

A synthesis of post‐esterified oxidized starch accompanied with physicochemical property analysis and esterification reaction condition optimization

“…Figure 2 shows the FTIR spectra of the native, esterified and post‐esterified oxidized starches. Generally, all spectra are similar in macro and three major peaks near the wavenumbers of 3379, 2931, and 1649 cm ¯ 1 are observed, corresponding to the vibrations of OH, CH 2  and water molecule within starch 2,4,6,20,24–25 . As numerous OHs are within starch macromolecule chain framework it is hydrophilic, readily to absorb water.…”

“…Generally, all spectra are similar in macro and three major peaks near the wavenumbers of 3379, 2931, and 1649 cm ¯1 are observed, corresponding to the vibrations of OH, CH 2 and water molecule within starch. 2,4,6,20,[24][25] As numerous OHs are within starch macromolecule chain framework it is hydrophilic, readily to absorb water. Numerous water molecules can be adsorbed on starch granule with a content higher than 13 wt% normally.…”

“…Where, chemical modification is widely used like esterification. [1][2][3][4][5][6][7][8][9][10][11][12] It can change starch molecule chain structure greatly, converting alcohol OH to ester group, altering macroscopic property such as hydrophilicity efficiently. Its variation is qualitative.…”

“…Numerous technologies such as physical, chemical, or enzymatic treatments can be used to in its modification. Where, chemical modification is widely used like esterification 1–12 . It can change starch molecule chain structure greatly, converting alcohol OH to ester group, altering macroscopic property such as hydrophilicity efficiently.…”

Influence of Moisture Content on Starch Esterification by Solvent‐Free Method

“…To meet various non‐food application requirements, starches have been modified chemically, physically, and enzymatically in multiple ways. [ 1–3 ] Among those methods, chemical modifications of starch have been developed for more than hundreds of years, and so far, there are many different modified starches available in the market. However, most chemical modifications of starch, such as esterification, are carried out in aqueous solution or organic solvents, including pyridine, dioxane, tetrahydrofuran, and dimethyl sulfoxide, [ 4–7 ] often toxic and cause environmental pollutions.…”