Study On The Effect Of Infrared Radiation On Lipid Metabolism Of Stored Rice

Rice is the main food crop in our country.Infrared radiation(IR)can control the adverse factors of safe storage of rice from the source and improve the stability of grain storage.Lipids are most closely related to the deterioration of rice quality,but the influence of infrared radiation on the lipid metabolism of rice is still unclear,which leads to the theoretical bottleneck of the application of infrared radiation technology in the inhibition and control of the deterioration of rice quality.The paper adopts the infrared radiation processing rice drying technology based on “Jing You 1 Hao” rice as raw material,and ambient air drying technology in the traditional drying(Ambient air drying,AAD)as contrast method,respectively,through the high temperature(35 °C)accelerated aging storage test and simulated low temperature(4 °C)storage experiment,the infrared radiation of the storage period of quality change rule and the influence of lipid metabolism.(1)By measuring indexes such as processing quality,surface color characteristics and oil oxidation characteristics of stored rice,comparing and analyzing the changing rules of rice quality at different storage temperatures and different drying techniques,it was found that infrared radiation had almost no effect on the processing quality of rice,after 240 d of storage,naturally ventilated and dried rice surface is grayer than infrared.In the oxidation property index of fats and oils,when stored at 35 °C,after 240 d of storage,the content of malondialdehyde in ambient air drying and infrared drying increased by 46.25 21.25 nmol/g,respectively,compared with 0 d.The fatty acid value of ambient air drying rice is 42.41±1.14 mg KOH/100 g,and the fatty acid value of infrared dry rice is 25.86 ± 0.52 mg KOH/100 g,which does not exceed the national safe grain storage standard;while the ambient air drying rice peroxide value is in the first 180 d It reached the maximum level of 18.66±1.15 g/100 g,and it dropped to 18.2±1.96 g/100 g when stored at 240 d.After 240 d of infrared radiation storage,the peroxide value was 15.53±0.41 g/100 g,and the treatment effect was significant(P <0.05);the contents of total saturated fatty acids(SFAs),monounsaturated fatty acids(MUFAs)and polyunsaturated fatty acids(PUFAs)in infrared radiation samples increased by 1.16,0.38 and 0.1 mg / g compared to the control samples,infrared dried rice The oil oxidation index is significantly lower than that of naturally ventilated rice,and the stability is better.(2)Headspace solid-phase microextraction combined with gas-mass spectrometry(SPME-GC-MS)was used to detect changes in volatile metabolites during rice storage.The volatile metabolites of rice during storage are mainly hydrocarbons,esters,alcohols,ketones,aldehydes and other compounds,among which hydrocarbons account for the highest content of volatile metabolites,followed by esters and aldehydes.Under the storage condition of 35 °C,the characteristic volatile substance hexanal of natural ventilated rice was not detected in the first 120 d,and the content was 49.55±5.59 ng/g at 240 days,which changed significantly.The content of hexanal in rice treated with infrared radiation was 30.75±4.15 ng/g at 240 d,which was significantly different from the content of control rice in the same period(P <0.05).The total content of aldehydes and ketones in infrared radiation was significantly lower than that of ambient air drying samples,infrared radiation samples were 118.10±13.35 and 4.62±0.69 ng/ kg,ambient air drying samples were 137.15±18.70 and 4.99±0.57 ng/g,respectively.The degree of oxidative degradation of lipid in infrared radiation rice was lower than that of ambient air drying sample,Infrared technology delayed the degradation of lipids to a certain extent and slowed down the aging of rice.(3)Using high-performance liquid chromatography-mass spectrometry(UPLC-QTOF-MS)combined technology,lipid metabolomics analysis of rice under different drying methods and different storage temperatures was performed to identify and analyze the differential metabolites stored in the rice and combine the metabolism Path analysis reveals the pathway of infrared radiation regulating rice aging rate.Through analysis of the metabolic profiles of PCA,OPLS-DA and other samples,1389 and 1241 kinds of metabolites were selected,including phospholipids,fatty acids and triacylglycerol.The results of pathway enrichment analysis showed that fatty acid biosynthesis,biosynthesis of unsaturated fatty acids,oleic acid metabolism,and linoleic acid metabolism are involved in the life activities of stored rice.In the fatty acid biosynthesis pathway,the palmitic acid and stearic acid content of infrared radiationdried samples decreased faster than that of naturally ventilated samples.It was found in the oleic acid and linoleic acid metabolism pathway that the downstream products of linoleic acid and oleic acid metabolism were aldehyde,alcohols,ambient air drying treatment of rice aldehyde,alcohol content changes faster than infrared treatment of rice,key metabolic enzymes(such as lipase,lipoxygenase,alcohol dehydrogenase,etc.)participate in lipid metabolism.(4)Using metabolic component screening technology,the key metabolic enzymes were screened out as lipase,lipoxygenase,alcohol dehydrogenase,etc.By measuring the activity of key enzymes,combined with indicators such as the quality of stored rice,it was found that during the storage process,the activities of lipase and lipoxygenase of infrared radiation treatment were lower.The lipase activities of infrared and natural ventilated rice were 2.9±0.6 and 4.13±0.83 U/m L,respectively,with significant differences(P<0.05).The ability of ambient air drying treatment to inhibit lipoxygenase enzyme activity was significantly lower than that of infrared treatment.Correlation analysis results show that the content of linoleic acid and oleic acid is closely related to the formation of aldehydes,and the content of oleic acid is closely related to lipase,lipoxygenase and alcohol dehydrogenase.The correlation coefficients of lipase,lipoxygenase and alcohol dehydrogenase were-0.913 **,-0.799 *,and-0.874 **,respectively,and the content of linoleic acid was significantly negatively correlated with lipoxygenase,and the correlation coefficients were-0.742*,respectively.It is found by comparison that under the action of infrared radiation technology,enzymes involved in the production of aldehydes are intervened in metabolic pathways,thus infrared radiation technology delays the oxidation of rice.