Study On The Degradation Effect And Mechanise Of Ochratoxin A By Electron Beam Irradiation

Ochratoxin A(OTA)is a mycotoxin produced by Aspergillus ochraceus and Penicillium verrucosum with strong nephrotoxic,hepatic toxic,neurotoxic,immunosuppressive,carcinogenic and teratogenic properties.Owing to its stability and refractoriness,OTA is spread widely in nature.It's hazardous to human and animal heath to consume food contaminated with OTA.Irradiation technology has been proved to be a kind of food preservation techniques with high efficiency and no pollution.At present,food irradiation technology has been considered as an effective method to deal with the mycotoxin contamination in agricultural products and ensure the food security by many countries and regions in the world.In this study,OTA was taken as an example of mycotoxin,and the aqueous solution,methanol-water(60:40),acetonitrile,white spirit and beer were taken as media.Then the effects of electron beam(EB)irradiation on the degradation of OTA in different media,the effects of EB irradiation on the quality of white spirit and beer,the radiolysis products in the aqueous solution,were evaluated.It was confirmed that OTA could be degraded effectively by irradiation technology,and provided a theoretical basis for the degradation of mycotoxins in other food by irradiation technology.The main contents and results of this investigation were showed as follows:1.The degradation effects and rule of OTA in aqueous solution were studied.The results showed that OTA could be degraded effectively by EB and y-ray radiation.OTA degradation rate was increased in an irradiation dose-dependent manner and EB radiation was more effective.At 5 Gy,the OTA degradation rate reached to 98%under both of the irradiation conditions.The OTA degradation efficiency was in the order of water>methanol-water(60:40,v/v)>acetonitrile in different solvents.It revealed that the organic solvent had inhibition effect on the degradation of OTA.The degradation rate increased significantly with a decrease of initial concentrations of OTA in aqueous solution.The pH value had an important influence in OTA degradation efficiency as well.A higher pH value could result in a higher degradation rate of OTA.OTA with the concentration of 0.1?g/mL could be degraded completely at 1 kGy in alkaline and neutral environment.H2O2 could improve the degradation rate of OTA at a concentration of 0.01 to 0.1%(v/v),while it was restrained at a concentration of 1%(v/v).What,s more,OTA degradation process agreed well with the pseudo first-order kinetic model(lnC/CO=-1.1431D+0.0049).EB irradiation was effective to degrade OTA in aqueous solution.2.The degradation efficiency of OTA in white spirit and beer and the effects of EB irradiation on the quality of wines were investigated.The white spirit and beer contaminated with OTA was irradiated by EB firstly,and then the OTA residual quantity and the quality of white spirit and beer were detected.The results showed that OTA could be degraded effectively in white spirit and beer by EB radiation.The degradation rate was increased depended on an irradiation dose-dependent manner.What's more,OTA degradation process in white spirit and beer agreed well with the first-order kinetic model.At 10 kGy,the degradation rate was about 65%and 21%in white spirit and beer,respectively.Obviously,the degradation of OTA in white spirit was more effective than that in beer.There was not significant effect of EB on the alcohol,pH value,reducing ability and DPPH scavenging ability of white spirit and beer at 10 kGy,while it had certain influence on the taste and flavor.Whether EB had adverse effects on the quality of wines,a further study was needed.3.The radiolysis products of OTA solution were preliminarily analyzed and the toxicity of products was evaluated as well.20?g/mL OTA solution was irradiated by EB at 5 kGy,and then the radiolysis was analyzed by HPLC-Q-TOFMS method.The molecular formulas and structures of six products were obtained.Four of them were phenylalanine,2-amino-3-cyclohexyl-propionic acid,2-[(6-chloro-4-methyl-2-oxo-2H-color full-7-based)oxy]propionic acid and OTB,respectively.The product left hadn't been reported.The search results in related toxicity databases indicated that there was only two products with toxicity much lower than OTA and other four products no toxicity.