| Peanut oil is the main edible plant oil in China, which obtained by the technique of pressing peanut. However, peanut can be easily contaminated by Aspergillus flavus, and then produce aflatoxins at the conditions of high temperature and humidity. Aflatoxins are secondary fungal metabolites with highly toxicity, and considered as class I carcinogen by International Cancer Organizations. Presently, the research in detoxification or reduction of aflatoxins in peanut oil becomes the focus in the world. In this study, an UV irradiation reactor had been designed and produced by us. It was used to study the UV detoxification efficiency of AFB1in peanut oil. In addition, the quality and safety of peanut oil were investigated and assessed after UV irradiation. The detailed results are as follows:1) The UV irradiation reactor designed by us includes conveying system, UV irradiation system, cooling system and oil storage system. Among these sections, the UV irradiation system is the core of the reactor, which includes detoxification room, UV lamp, fluid guiding plate, and fluid distributing pipe. The reactor has a proper structure, which can be operated easily and safely without pollution to environment. It can be operated continuously and applied in large-scale production in the oil industry.2) The main factors affecting the detoxification efficiency of AFB1in peanut oil are.UV wavelength, irradiation intensity, and irradiation time. The optimal experimental design and response surface methodology were employed in this study. The optimal detoxification conditions of AFB1in peanut oil were as followed:at the room temperature, the UV lamps (power36W) with a wavelength of365nm, irradiation intensity of6.4mW/cm2, and irradiation time of9.5min. Under the optimal detoxification conditions, AFBi in peanut oil was decreased from51.96±4.24ug/kg to5.18±0.38ug/kg, and reduced by90.03%. The residue of AFB1in peanut oil was far less than20ug/kg, a limit level set by GB1534-2003. In addition, the degradation rate of AFB1in peanut oil was closely related to UV irradiation time, and the relation equation was y=10.174x+35.095(R=0.997).3) The light value of peanut oil was increased significantly (P<0.05) after UV detoxification, so photodegradation treatment could improve the color of oil effectively. After10min of UV irradiation, the acid value decreased from1.37mg/g to1.41mg/g, and the POV decreased from3.34mmol/kg to3.49mmol/kg, reduced by2.9%and4.5%, respectively. The acid value and POV of peanut oil were all less than the limit levels set by GB1534-2003(acid value<4.0mg/g, POV<7.5mmol/kg). The oleic acid content decreased from34.18±0.34mg/100mg for the untreated oil to32.21±1.23mg/100mg for the treated one in10min of irradiation (P>0.05), meanwhile, the linolic acid, linolenic acid, and eicosenoic acid were significantly decreased by8.72%,18.18%, and5.88%, respectively, compared with those of the control (P<0.01). The results revealed that UV irradiation obviously affected the unsaturated fatty acids of peanut oil, and their decreases were time dependent.4) The safety of peanut oil was evaluated after UV irradiation by Ames test and HepG2cell cytotoxicity test. The results from the Ames test showed that UV irradiation significantly decreased the numbers of revertants (P<0.01) of the TA98and TA102induced by AFB1in peanut oil, and no mutagenicity was detected in aflatoxin-contaminated peanut oil after being irradiated. The results from HepG2cell viability furtherly verified that the toxicity of AFB1in peanut oil was significantly reduced, compared with the positive control. The cell viability of HepG2cells treated.with peanut oil containing AFB1extract significant increased (P<0.01), and reached to95.54±1.19%at10min of UV exposure, which was statistically insignificant difference (P>0.05) compared with that of the negative control. |
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