Research On Contaminations And Production Mechanisms Of Fusarium Toxins In Stored Cereals

Fusarium toxins are a class of toxic secondary metabolites produced by Fusarium,widely present in cereals,which can not only affect the yield and quality of cereals and cause huge economic losses,but may also enter animals and humans through the food chain.serious harm to their health.China is a major cereals producer in the world,with tens of millions of tons of cereals stored annually and the storage time is long.During the storage process of cereals,mold growth and mycotoxin contamination often occur,resulting in food safety hazards and huge economic losses.Therefore,it is of great practical significance to effectively monitor the contamination of Fusarium toxins in stored cereals and explore the occurrence of Fusarium toxins in cereals during storage.The storage wheat and paddy of Shanghai Pujiang Storage Co.,Ltd.as this research object,and mainly carries out the research work in the following aspects:1.Investigation on the contamination of Fusarium toxins in harvested cereal samples:Based on the Qu ECh ERS purification method and the UPLC-MS/MS detection method,the contents of 18 common Fusarium toxins in 181 harvested cereals were detected.The results showed that 13 kinds of Fusarium toxins were detected in 138 cereal samples,and the contamination rate is 0.55%-68.51%.Among all cereal samples,deoxynivalenol（DON）was the most common mycotoxin,with a contamination rate of68.51%and the most and average contamination level of 326.58 and 59.37μg/kg,respectively.The next was fumonisin B₁（FB₁）,the contamination rate was 31.49%,and the most and average contamination level was 907.57 and 147.37μg/kg,respectively.21%of cereals were co-contaminated with 2 or more Fusarium toxins,and the positive wheat samples were co-contaminated with up to 4 kinds of Fusarium toxins,and the paddy was co-contaminated with up to 6 kinds of Fusarium toxins.There are no samples of harvested cereals that Fusarium toxins exceed the allowable limits standard.2.Research on the occurrence of DON and its derivatives（important Fusarium toxins）under theoretical culture conditions:In view of the previous studies on Fusarium graminearum most of them focus on complex solid substrates,but it is difficult to measure the growth of mycelium,the ratio of nutrient components,and the p H of the environment.In the current research,the effects of different liquid culture conditions on the production of DON and its derivatives by Fusarium graminearum,the by the single factor investigation and response surface methodology.The results showed that under liquid culture conditions,the tested strain mainly produced DON and 15-acetyldeoxynivalenol（15-ADON）,but not 3-acetyldeoxynivalenol（3-ADON）.Incubation time and p H value exhibited an extremely significant and interactive effect on DON production,while a significant and interactive effect on the production of 15-ADON was shown by incubation time and incubation temperature.The optimal conditions for DON production were:incubation time of 22 days,temperature of 26.3℃,initial p H of 6.35 and the highest amount was 5739.69μg/L.The highest production for15-ADON with the concentration of 10453.41μg/L was achieved when the incubation time,the temperature and the initial p H were set as 21 days,26.3°C and 5.58,respectively.The research results would provide theoretical basis and data support for the biosynthesis,routine supervision and control of DON and 15-ADON.3.Study on the influencing factors of DON and its acetylated derivatives in cereals:Fusarium graminearum PH-1 was used as the test strain to simulate the process of Fusarium infecting cereals in the laboratory.The influence of environmental conditions（environment and substrate）on DON and acetylated DON were comprehensively evaluated.The results showed that the production of toxins was positively correlated with water activity,and the optimum temperature and time for mycotoxin production in different substrates had different trends.3-ADON and 15-ADON reached their maximum values on the 14th and 28th days under the conditions of 20℃and 0.98,respectively.The optimal production conditions of DON in paddy were 30℃,0.98 and 35 d,while 3-ADON and 15-ADON reached the maximum value on the 35th and 28th day under the conditions of 30℃and 0.98,respectively.The production of toxins is affected by various influencing factors,but at low temperature and low water activity,the production of each toxin was low.4.Research on production and distribution of DON and its acetylated derivatives in actual stored cereals:The contamination of Fusarium toxins in 180 stored cereals was analyzed,and DON was the most common mycotoxin in stored cereals,with a contamination rate of 50.00%.The effects of storage cereals type,region,quality,storage location and storage process（temperature and time changes）on the contamination level of DON and its derivatives were analyzed.The results showed that different substrates had no significant effect on the contamination level of DON and its derivatives.The contamination rate of DON in wheat in Jiangsu and Shandong was significantly higher than that in Anhui（P<0.01）,and the contamination rate of DON in white wheat was significantly higher than that in red wheat（P<0.01）.Second-class paddy was significantly higher than that in first-class paddy（P<0.05）.There was no significant difference in the contamination of DON and its derivatives in different storage sites（upper,upper middle,lower middle and lower layers）.The DON contamination rate in stored wheat and paddy did not change significantly with time,the contamination of acetylated DON in stored cereals is relatively light.During the storage process,its changes are jointly affected by temperature,time and substrate type.This research results can provide data reference and theoretical basis for the supervision and control measures of mycotoxins in stored cereals.