Abstract: In this paper, arrowhead starch was modified by wet oxidation with hydrogen peroxide (H2O2) as oxidant and copper sulfate (CuSO4) as the catalyst. And the properties of starch before and after oxidation were discussed. Single factor experiments were designed to investigate the effects of additive amount of H2O2, CuSO4, pH value and reaction time on the oxidation of arrowhead starch. Based on the single factor experiment, the carboxyl content and transparency of starch were taken as the response value to design the response surface experiment so as to optimize the preparation process, and the properties of arrowhead starch before and after oxidation were tested. The best oxidation process was obtained as follows: 31.6 ml of H2O2 was added into starch emulsion solution (100 g, 40%, w/w) to have pH at 8.35, the amount of CuSO4 was 0.04% of the dry basis, and the reaction time was 4 hours at 45 ℃. The carboxyl content of the oxidized arrowhead starch was 0.355%, and the transparency was 52.6%. The solubility and swelling degree of oxidized starch increased significantly with the increase of temperature. The coagulability of oxidized starch was better than before; the freeze-thaw stability was worse; the viscosity was lower, and the gelatinization temperature of starch became lower. The particles were broken greatly and the shape increased; in the infrared spectrum, the absorption peak of 1 760-1 660 cm-1 was sharper and stronger, and the carboxyl vibration was enhanced. The X-diffraction characteristic diffraction peak of oxidized starch became higher, and the crystallinity increased from 44.80% to 55.11%. In conclusion, the arrowhead starch oxidized by H2O2/CuSO4 has high carboxyl content and high transparency. At the same time, the physical and chemical properties, particle state and crystal structure change, which provides a theoretical basis for the development and utilization of the oxidized arrowhead starch.
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