Study On The Mechanism Of Effect Of Electron Beam Irradiation On Lipids Of Indica Paddy During High Temperature Storage

Rice is the most important food crop in China,and its storage effect is closely related to food security in China.Indica rice needs higher temperature and humidity than japonica rice,so it is mostly planted in southeastern China.As the quality of paddy is easy to deteriorate under high temperature,how to ensure that indica rice can maintain good quality in storage under high temperature in the south china is an important problem to be solved in our country.The deterioration of paddy quality under high temperature is mainly caused by lipid oxidation and metabolism in paddy.As an environmentally friendly and convenient technology,electron beam irradiation has a good effect on inhibiting lipid oxidation metabolism and delaying the deterioration of paddy quality during paddy storage.In the process of storage,the deterioration rate of paddy quality under the condition of high temperature and high humidity was higher than that of paddy stored at high temperature and low humidity.The results show that electron beam irradiation can improve the quality deterioration of paddy under two storage conditions.In this study,Fengliangyou was used as raw material to study the mechanism of electron beam irradiation to delay lipid deterioration in indica rice.the main contents and results are as follows:1.Paddy was treated by electron beam irradiation,and the water content,water distribution,crude fat content,fatty acid value,peroxide value,malondialdehyde,electrical conductivity,microstructure,activities of enzymes related to lipid metabolism and m RNA expression during paddy storage were measured.Electron beam irradiation optimized the water content and distribution of paddy during storage.Electron beam irradiation delayed the increase rate of MDA content and the decrease rate of crude fat content during high temperature storage,and kept the peroxide value stable.After 100 days of paddy storage,the fatty acid value of the irradiation group was 24.58% and 32.21% lower than that of the non-irradiation group under the conditions of high temperature,low humidity and high humidity.It was observed by scanning electron microscope that the starch granules in the irradiation group were clearer after storage.After storage,the electrical conductivity of paddy in the irradiation group was lower than that in the control group,indicating that irradiation was beneficial to maintain the stability of paddy cell membrane during storage.After electron beam irradiation,the activities of lipase and phospholipase D in paddy decreased by 24.64% and 45.34%,respectively,which decreased the activity of lipoxygenase in paddy during storage,maintained the relative stability of peroxidase,and helped to slow down the deterioration of paddy lipids.2.The fatty acid composition of paddy was qualitatively and quantitatively analyzed by gas chromatography during storage.The fatty acid composition of paddy showed an upward trend as a whole.And the fatty acid groups of irradiated paddy increased more slowly.At the same time,electron beam irradiation increased the ratio of unsaturated fatty acids to saturated fatty acids from 1.95 to 2.96,which improved the nutritional value of paddy.The volatile metabolites of paddy were determined by GC-MS.In the initial samples,unirradiated hydrocarbons,aldehydes,alcohols and ketones accounted for 39.10%,12.54%,8.07% and 8.82%.The proportion of hydrocarbons,aldehydes,alcohols and ketones in the irradiation group was 30.90%,20.72%,6.82% and 12.71%.After electron beam irradiation,the proportion of hydrocarbons and alcohols decreased,while aldehydes and ketones increased.After irradiation,the increase of aldehydes in the storage process decreased,and the types of alcohols increased.Irradiation decreased the esters with the storage time,and increased the contents of phenols and quinones.At the same time,electron beam irradiation degraded methoxybenzoxime and other pollutants,resulting in a significant decrease in its content.In summary,electron beam irradiation helps to reduce the bad flavor produced by lipid metabolism and delay the deterioration of paddy flavor.3.The deterioration of paddy quality during storage is closely related to paddy lipid metabolism.UHPLC-Q-Extractive Orbitrap Mass was used to analyze the liposome of different treatments of paddy during high temperature storage,to identify and analyze the differential metabolites in paddy storage,and to analyze the metabolic pathway of related metabolites,in order to reveal the law of lipid metabolism during paddy storage and the mechanism of regulation by electron beam irradiation.The results showed that phospholipid sphingomyelin and other membrane lipids in paddy cell membrane were hydrolyzed by related hydrolytic enzymes to produce fatty acids,which were further oxidized and decomposed into various peroxides and bad volatile flavor compounds.Electron beam irradiation can effectively inhibit the pathways related to lipid metabolism,delay membrane lipid metabolism and reduce the production of fatty acids,so as to maintain paddy quality and delay paddy aging.