Study On Main Mycotoxin Contamination Levels And Rapid Identification Techniques In Stored Wheat And Paddy

Mycotoxins are toxic secondary metabolites produced by toxigenic fungi and have toxic effects on humans and animals.It mainly includes carcinogenicity,teratogenicity,mutagenicity,immunosuppression,embryotoxicity,reproductive disorders,hepatotoxicity,nephrotoxicity and neurotoxicity.Mycotoxins can not only contaminate grain before or after harvest,affect grain yield and quality and cause economic losses,but also enter animals and humans through the food chain and endanger human health.How to reduce and control the harm of mycotoxin to grain has become a global concern.However,there have been few reports of contamination with mycotoxins in stored cereals.Therefore,it is of great practical significance for the safe storage of wheat and rice to effectively monitor the contamination of mycotoxins in storage grains such as wheat and paddy and explore the occurrence rules of mycotoxins in the storage process of wheat and paddy.This paper mainly carries out the following research work:1.Preliminary identification of wheat and paddy virulent strains in Shanghai Pujiang Warehousing Co.,Ltd.Wheat of the communist party of the fungus were isolated by 17 strains,belonging to 12 kinds,namely,including Aspergillus ruber,Eurotium chevalieri,Pyrenophora graminea,Aternaria tenuis,Moniliales,Alterneria tenuissima,Aspergillus amstelodami,Aspergillus aeruginosa,Coprinus radians,Helmiinthosporium,Alternaria alternata,and Aspergillus fumigatus,one of the largest number of Alternaria alternata,accounting for 23%of the total number of strains.A total of 86 strains of fungus were isolated from paddy,belonging to 12species,including Phoma,Basidiomycotina,Epicoccum,Lichtheimia,Asperigillus flavus,Aspergillus aeruginosa,Penicillium aureus,Sclerotium aspergillus,Talaromyces,Chaetomium,Aspergillus fumigatus and Trichoderma longibrachiatum.The number of Aspergillus flavus was the largest,accounting for 47.7%of the total number of strains.2.Study on the contamination of stored wheat and paddy.In this study,40mycotoxins in grain were detected simultaneously by UHPLC-MS/MS.The results showed that 27 mycotoxins were detected in 119 wheat samples,and 22 mycotoxins were detected in 60 paddy samples.The detection rates of deoxynivalenol and tentoxin in wheat were 33.61%and 80.67%,respectively,and the mean contamination concentrations were 96.95?g/kg and 24.09?g/kg,respectively.A total of 22 toxins were detected in paddy,among which the contamination levels of fusarenon X and fumonisin B₁ were higher,with detection rates of 33.33%and46.67%,respectively.The mean contamination concentrations were 3.96?g/kg and19.91?g/kg,respectively.The mycotoxin contamination of grain harvested in recent years was detected,it was found that the contamination of mycotoxins in wheat harvested in 2019 was relatively more serious,while that of paddy harvested in 2018was relatively more serious.The contamination level of mycotoxin in grain from different producing areas also varied.Compared with Shandong,the contamination level of wheat from Jiangsu producing area was more serious.Paddy contamination levels in Shanghai are generally higher than in Heilongjiang.In addition,during the storage of wheat and paddy,aflatoxin B₁,aflatoxin G₁,aflatoxin M₂,ochratoxin A,ochratoxin B,DON,T-2 toxin and HT-2 toxin detection rate increases with the extension of storage time.3.Rapid identification of DON in wheat by electrochemical sensor based on nitrogen-doped Cu-MOFs(N-Cu-MOF)nanomaterials.An electrochemical aptamer sensor driven by N-Cu-MOF nanomaterials was established for rapid detection of DON.N-Cu-MOF was used as electrode substrate material to establish a sensing platform with high sensitivity and good selectivity.N-Cu-MOF as the electrode substrate material makes the sensor has the excellent characteristics of large specific surface area and can be combined with the aptamer,and at the same time,it can be used as an electrical signal probe.When the DON concentration was 0.02-20 ng/m L,the linear relationship of the N-Cu-MOF aptamer to DON was good(R²>0.99),and the detection limit was as low as 0.008 ng/m L.In addition,the N-Cu-MOF sensing platform also has good selectivity and reproducibility,with satisfactory recoveries(95.6?105.9%)obtained in actual wheat samples.This strategy can be easily extended to other mycotoxins or other harmful substances by changing the specific aptamer,and has a broad application prospect.