| New harvest indica rice variety Gang you527, glutinous rice variety Yi gen miao were used as raw material in this paper, rice was treated in high temperature and humidity conditions of40℃, RH85%for4d, at the storage temperature of15℃and30℃, changes in moisture content, MDA, protein, PPO activity and carbohydrate content of rice was studied, and the SEC-MALLS-RI system was used to determine the weight average molecular and molecular radius of gyration of rice during storage, to explore the relationship between these changes and the rice aging mechanism, conclusions are as follows:1. The initial germination rate of the two rice varieties were improved at the aging treatment condition of40℃, RH85%, and maintained a high germination rate during storage. Aging treatment increased the rice fatty acid value, in the storage time of180days, fatty acid value of Gang you527and Yi gen miao increased20.85mgKOH/100g and19.24mgKOH/100g respectively. The increased PPO activity inhibited the rise of MDA, high temperature and humidity treatment can stimulate antioxidant enzyme activity in the short term. Aging postponed respiratory peak of Gang you527, brought forwad the respiratory peak of Yi gen miao. The low temperature of15℃is conducive to maintain the low respiration of rice, delay quality deterioration.2. Accumulation peaks of water-soluble protein, salt-soluble protein and alcohol-soluble protein show in30d. gluten content shows rapid accumulation in60-90d, gluten/gliadin ratio reached its peak. Sulfhydryl content decreased during storage, sulfhydryl is oxidized into a disulfide bond, Glu/Gli protein ratio increases.The different varieties of rice in the same storage conditions vary greatly in sulfhydryl content.3.40℃, RH85%aging treatment reduced the initial value of amylose content of Gang you527, it increased about2%during the storage time. Gel filtration chromatography of Gang you527shows that shoulder of amylose broadens due to the amylopectin degradation. 4. During storage time0d to420d, using SEC-MALLS-RI,the Mw value of Gang you527range from1.195×108～1.343×108, RMS value range from246.9～262.3nm; Yi gen miao Mw value range from2.071×10～2.841×10, RMS value range from354.9～405.8nm.The molecular weight distribution shows that Mw value of two varieties of rice decreased, aging treatment accelerate this trend. Amylopectin debranching leads to the Mw decrease of natural starch. In addition, the RMS of the indica rice is lower than the glutinous rice, indicates that amylose might affect the dispersion of natural starch in solution. |
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