Physicochemical Properties Of Hydropropyl Oxidized Corn Starches Varying In Amylose Content

The effect of amylose content on physical-chemical characters of hydroxypropyl corn starches and oxidized corn starches as well as hydroxypropyl-oxidized corn starches and oxidized-hydroxypropyl corn starches were investigated with corn starches including waxy corn starch(WC), common corn starch(CC), and high amylose corn starches(AMC) used as the raw material. The results were showed that amylose content have a significant impact on hydroxypropyl and oxidized corn starches no matter under single- or dual- modification as followed:The preparation of hydroxypropyl corn starches(called HPS for short) etherified with propylene oxide and oxidized corn starches(called oxy-S for short) oxidized with sodium hypochlorite varying in amylose content was studied. The results were showed that, substitution degree of hydroxypropyl of hydroxypropyl corn starches increased with increasing amylose content and carboxyl and carbonyl content contrary, which indicated high amylose content is advantageous to etherification efficient and oxidation efficient contrary. And high amylose content had a positive impact on hydrophilicity of hydroxypropyl corn starches. The oxidized corn starches with low amylose content had a better anti-retrogradation and transparency. The variation range of viscosity of modified starch was determined by the amylose content, as high amylose content corn starch with low viscosity and low amylose content corn starch with high viscosity.The preparation of hydroxypropyl high amylose corn starches and oxidized high amylose corn starches varying in the content of etherifying agent and oxidizing agent was studied. The results were showed that, the water-solubility of hydroxypropyl high amylose corn starches were significantly improved with the increasing level of etherification, while the peak viscosity of the starches were promoted little. The relative crystallinity of the two modified high amylose corn starches both decreased with the increasing level of modification. The carboxyl content of oxidized high amylose corn starches increased obviously with the increase of the level of oxidation, while carbonyl content increased little in a small amount. However, the water-solubility of oxidized high amylose corn starches were improved little with the increase of the level of oxidation.The preparation of varying in the amylose content was studied. The results were showed that, under this order of modification, high amylose content retarded the downtrend of the substitution degree of hydroxypropyl and the uptrend of the carbonyl and carboxyl content by oxidation. The gelatinization temperature and gelatinization enthalpy of the three kinds of dual-modified starches were both decreased and the higher amylose corn starch decreased less. The variation range of viscosity of dual-modified starches was determined by the amylose content, as high amylose corn starch with lowest viscosity and waxy corn starch with highest viscosity. Oxidization had the top effect on dual-modified waxy corn starch and the minimal on dual-modified high amylose corn starch.The preparation of The preparation of oxidized-hydroxypropyl corn starches varying in the amylose content was studied. The results were showed that, dual-modified starches were influenced more by the former modification, as oxidized-hydroxypropyl corn starches had higher degree of oxidation and hydroxypropyl-oxidized corn starches had higher degree of etherification. The main difference of Gelatinization properties between the two dual-modified starches was peak viscosity, as oxidized-hydroxypropyl corn starches had the lower one. The amylose content determined whether the starches could take the advantage of the modification, as lower amylose corn starches be better for oxidization and higher amylose corn starches be better for hydroxypropyl etherification.