Effects Of UV Irradiation On Microbial Inhibition And Mycotoxin Degradation On Wheat Grain Surface

Ultraviolet is widely used in drinking water disinfection,medical disinfection,air purification and disinfection,food and packaging materials surface contamination control,instant food sterilization and fruit and vegetable storage and processing.Ultra violet disinfection has the advantages of no residue and no secondary pollution.In this paper,the bactericidal effect of different wavelengths of ultraviolet light on the surface microorganisms of wheat grains and the degradation effect of mycotoxins in wheat grains were studied.The main conclusions are as follows:（1）The effects of ultraviolet wavelength,irradiation time,irradiation distance and ambient temperature on the bactericidal effect of microorganisms on the surface of wheat grains were studied.The bactericidal effects of ultraviolet lamps with wavelengths of 185 nm and 254 nm on the surface microorganisms of wheat grains in different states（wheat grains,wheat grains after watering,and wheat grains after tempering）were investigated.The results showed that 185 nm,254 nm,260 nm,274 nm and 283 nm ultraviolet rays had better sterilization effect on the surface of the plate.When irradiated for 20 s,the sterilization rate could reach 100%.The UV lamp with the power of 80 W and the wavelength of 185 nm had better sterilization effect on aerobic plate count in wheat grains,wheat grains after watering and wheat grains after tempering,and the maximum sterilization rates were 88.8%,79.5%and 82.9%,respectively.（2）DON,AFB₁,FB₁,OTA and ZEN were irradiated by 185 nm,222 nm,254 nm,260nm,274 nm,283 nm,307 nm,366 nm and 395 nm,respectively.The results showed that the UV wavelength had a significant effect on the degradation effect.185 nm,254 nm and 260nm ultraviolet rays had better degradation effect on DON,and the degradation rate exceeded80%after 100 min irradiation.The degradation effect of 366 nm and 395 nm ultraviolet rays on DON was not significant.AFB₁ could be degraded by 9 kinds of wavelength ultraviolet rays,among which 366 nm,254 nm and 260 nm ultraviolet rays had better degradation effect.When irradiated for 80 min,the degradation rate exceeded 45%,and the degradation effect of274 nm ultraviolet rays was relatively poor.Except for 366 nm and 395 nm ultr aviolet rays,other wavelengths of ultraviolet rays can degrade FB₁,among which 222 nm and 260 nm ultraviolet rays have better degradation effects,and the degradation rate exceeds 47.9%when irradiated for 100 min.OTA could be degraded by all 9 wavelengths of ultraviolet light.The degradation rate of 185 nm,222 nm,254 nm,260 nm,274 nm and 307 nm ultraviolet rays exceeded 89.9%after 100 min of ultraviolet irradiation.The UV degradation rate at 395 nm was the lowest,which was 49%.After UV irradiation at 185 nm and 222 nm for 100 min,the content of ZEN increased with the increase of irradiation time.After UV irradiation at other wavelengths,the content of ZEN increased significantly and then decreased significantly（3）Wheat grains and flour contaminated by DON were irradiated with nine wavelengths of ultraviolet light.The degradation effect of 366 nm and 395 nm ultraviolet rays on DON in wheat grains and wheat flour was not significant.The degradation rate of DON in wheat grains was about 16%,and the degradation rate of DON in wheat flour was about 6%.The degradation rate increased significantly with the increase of irradiation time and irradiation intensity.After UV irradiation,the moisture content of wheat grain and wheat flour decreased significantly,and the wet gluten content and protein content did not change significantly.The above studies preliminarily proved the effects of different ultraviolet rays on microbial sterilization and mycotoxin degradation,thus providing theoretical support for the application of ultraviolet rays and the degradation of mycotoxins.