Abstract: 【Objective】Due to the loss of protection of endosperm, rice prones to aging during storage, mildew and other issues, which resulted in edible quality deterioration or even lost edible value. The aim of this study was to explore the reasons for the deterioration of rice quality by measuring the content of total acids and free fatty acids, changes in fatty acid composition and content, microscopic structure of cross-sectional endosperm cells or starch granules of rice, and to provide reference for storage technology of rice. 【Method】The No. 99 japonica rice packaged in woven, natural airtight anoxia and vacuum was simulated storaged in artificial climate chamber at a temperature of 15, 25, and 30℃ under 60% RH for 180 d, then the quality indicators and morphology of rice were measured every month. The aging mechanism of rice and variation of starch granules morphology caused by lipids and cross-sectional structure of endosperm after deterioration were explored by determining the variation of fatty acid and total acid value, the changes of fatty acid composition and content were analyzed by gas chromatography, and the cross section of rice endosperm cell morphology was observed by scanning electron microscopy.【Result】It was found from the study that the free fatty acids and total acid contents of rice packaged in woven and natural airtight anoxia increased sharply in initial process while decreased with a serious deterioration of the quality. The free fatty acids and total acid contents of rice packaged in vacuum maintained at a relatively stable level while the storage temperature had no significant effect on its content. The most abundant fatty acids were linoleic acid, oleic acid and palmitic acid,which accounted for more than 90% of total fats. Packaging methods and storage temperature had a great impact on various fatty acids. In addition to arachidonic acid (C20:0) and docosenoic acid (C22:1), the other kinds of fatty acids were greatly influenced by packaging methods. The storage temperature had a significant relationship with myristic acid (C14:0) and behenic acid (C22:0) while had little effect on the rest of the fatty acids. The changes of fatty acids agreed with the results that the amount of highly unsaturated fatty acids decreased with increasing temperature, these data also demonstrated negative correlations between polyunsaturated fatty acids (stearic acid (C18:0) and oleic acid (C18:1)) and saturated or monounsaturated fatty acids (linoleic acid (C18:2) or linolenic acid (C18:3)). The starch grains of fresh rice exist in a compound grain form with a large shape and a thick film on the surface, neat and orderly arranged with clear radial section in both sides of the sheet between the cells. The structure of endosperm cell cross-section became sloppy and disorderly, while the number of intracellular sections were more than that of intercellular sections. In addition, some “small holes” can be observed in sections with some protein and fat droplets scattered in the amyloplast. The compound starch granule broke into a large number of single granulocytes due to the damage of cell wall. Part of the shape of single starch granules became nearly circular with some blunt edges. And the radial structure became blurred or even disappeared when aging seriously.【Conclusion】The value of fatty acids and total acid showed an upward trend first and then a downward trend, the smoothness of endosperm surface deteriorated, and the number of holes and tilt of surface proteins film increased, as well as the radial structure trend disappeared gradually during storage. The rice quality deterioration seriously with woven and natural hypoxic packaging, it could delay the deterioration process of rice quality with vacuum packaging effectively.

Key words: rice, fatty acids, total acid, gas chromatography, endosperm cell