Study On Degradation Of Aflatoxins In Peanuts

Aflatoxins （AFTs）, a group of potent carcinogenic and teratogenic compounds, are secondarymetabolic products of some fungus, such as Aspergillus flavus, Aspergillus parasiticus and Aspergillusnomius. It produces a wide range of adverse and toxic effects in animals in addition to being foodbornehazards to humans. Aflatoxin has stable physical and chemical properties, which makes it difficult to bedestoried in the process of food processing. Peanut is one of the most important oil crops in China aswell as agricultural products with export advantage. It plays a key role in earning foreign exchangethrough exports and improving the international competitiveness. In recent years, the consumption andinternational trade of peanut in our country were seriously threatened by aflatoxin contamination, whichhas become a potential risk for the development of peanut industry. It is essential to make aflatoxincontents of food and feedstuff to a safe level by developing degradation technologies. In this research,ultraviolet （UV） light and ozone fumigation were chosen to conduct the degradation for the aflatoxin inpeanut, repectively. The changes of nutritional quality of peanut after the degradation and thedegradation mechanism and radiolysis products by UV irradiation of AFB1were preliminarily discussed.The results are listed as follows:1. The effects of UV on degradation of aflatoxin in peanut were studied. The results showed that thedegradation rate of AFB1increased with the increasing of exposion time and UV lamp power, and UVlight with254nm would be better efficient on degradation than365nm.1kg peanuts were treated withUV at the condition of wavelenth of254nm, power of15W, irradiation distance of10cm, tile area of30cm×40cm and irradiation time of3h. Then these samples were placed for two weeks at the roomtemperature. Its acid value, peroxide value, polyphenol and resveratrol had no significant differencewith that of control group.2. The effects of UV on the degradation of AFT in methanol solution were studied. Results showedthat the degradation of AFB1and AFG1was much easier, and no degradation of AFB2and AFG2washappened. Four standard solutions （10μg/mL） of AFB1, AFB2, AFG1and AFG2were treated with UV atthe condition of wavelenth of254nm, power of15W and irradiation time of30min, respectively. Theresults of HPLC showed, the concentration of AFB1and AFG1visibly decreased, whereas concentrationof AFB2and AFG2had no change. Continued exposure to UV light for1or2hours, the concentration ofAFB2and AFG2had no change just yet. This demonstrated that UV only could degrade AFB1and AFG1,and had no degradation for AFB2and AFG2in methanol solution.3. Two UV radiolysis products of AFB1in methanol solutionwas were found by LC-MS/MS. Thecondensed structural formulas of two radiolysis products were C17H14O6and C14H10O6,whose molecularweights were314.70and274.77, respectively. The formation process of ion fragments were speculatedaccording to the structers of parent ions. All possible pyrolysis products were displayed in MSspectrographic.4. We designed a dedicated device applied in the ozone degradation for aflatoxin. The optimumdegradation condition for aflatoxin and its effects of three aspects （ozone concentration, treatment time and moisture content of peanut） were discussed. Results showed that, aflatoxins in peanuts at moisturecontent of5%（w/w） were sensitive to ozone and easily degraded when reacted with6.0mg/L ozone for30minutes at room temperature. Under this condition, the degradation rate of the total AFT and AFB1was65.8%and65.9%, respectively. In general, ozone had better degradation effect for aflatoxins G thanaflatoxins B. Moreover, it had the highest degradation efficiency on AFG1with the rates of degradationwas70%, and had the lowest degradation efficiency on AFB2with the rates of degradation was40%.5. Aflatoxins extraction from peanuts was treated with6.0mg/L ozone gas. The results showed thatAFB1and AFG1were more sensitive to ozonation than AFB2and AFG2. AFB1and AFG1weredetoxified completely in short time. However, AFB2and AFG2would need long time up to2hours to bedetoxified significantly.6. According to ozone oxidation mechanism of three steps and reports about AFB1degradation byozonayion, we speculated some possible products of AFB1and AFG1by ozonation, whose molecularformulas were C₁₇H₁₂O₁₀，C₁₈H₁₆O₁₁，C₁₆H₁₀O₇，C₁₆H₁₀O₁₀，C₁₇H₁₂O₁₀, respectively. This would providereference for futher study.