Application Research Of GC-IMS Continuous Technology In Early Monitoring Of Rice Mildew

Due to the loss of protection from chaff and the exposure of nutrients in the air,rice is prone to mildew during storage,which causes a loss of about 1 million tons annually in China.In the early stage of mildew,the quality of rice does not change significantly.Therefore,there is an urgent need for a method to accurately determine the early mildew of rice,and to control the crisis in the bud.In recent years,Gas Chromatography-Ion Mobility Spectrometry(GC-IMS)has been developed rapidly and is widely used in food quality safety testing and process control.Therefore,this study used mildewed rice as the research object,obtained the dominant microorganism strains causing rice mildew in southern regions of the Yangtze River through separation and purification.Moreover,GC-IMS technique was used to characterize the mildew process of rice,and change of volatile organic compounds was used to evaluate the degree of mildew.The main contents and results are as follows:(1)Using mildewed rice as the research object,the traditional microbial separation method combined with molecular biology identification was used to screen and identify the dominant microorganism strains causing rice mildew in Zhenjiang,Jiangsu Province.The test results showed that Aspergillus niger,Aspergillus flavus,Aspergillus parasiticus,Penicillium janthinellum,Penicillium variabile and Penicillium funiculosum are the dominant fungi causing rice mildew in southern regions of the Yangtze River.(2)The main parameters of the GC-IMS instrument were optimized and analyzed.Volatile organic compounds from the growth metabolism of six molds were determined under optimal conditions.The results showed that the characteristic volatile organic compounds of different fungi had common characteristics,and a few of them were specific to a certain strain.It was proved that these volatile organic compounds could be used to characterize the mildew state of rice.(3)The variation pattern of volatile organic compounds produced during the mildew process of rice was studied via GC-IMS technology.The degree of mildew of natural mildew rice was determined by combining the artificially inoculated molds of moldy rice.The results showed that the results of the characteristic peak image library combined with chemometrics could effectively distinguish the early mildew degree of rice,demonstrating that GC-IMS has great potential in early warning of rice mildew through analyzing changes of volatile compounds during mildew process(4)Rice samples with different storage years were used as the research object,and applicability of the 21 characteristic peaks selected in the previous period was tested by comparing the detection results of GC-IMS instrument with the results of judging mildew degree of rice according to fatty acid content.The results showed that the 21 characteristic peaks selected can be used to analyze and judge mildew degree of rice samples in the granary.The results indicated that GC-IMS technology can be applied to monitor the degree of rice mildew in granaries to reduce economic losses(5)In order to verify the generalization ability of the established rice mildew monitoring system to other rice varieties,the applicability of the selected characteristic fingerprint spectrum used to characterize the mildew process of glutinous rice was studied.The results showed that the monitoring system was not suitable for the degree of mildew of glutinous rice,which indicated that different kinds of rice need to have different monitoring systems.