| The Aflatoxins (AFT) are secondary metabolites produced mainly by Aspergillus flavus and Aspergillus parasiticus, which occur extensively on oil crops, such as peanuts, corns and their products. Due to their high toxicity to human beings and animals, many countries in the world have strict limits for levels of aflatoxins in agricultural products. Every year, agricultural products rejected or destroyed by the importing countries due to aflatoxin contamination have resulted to huge economic losses in China. In addition, the incompatibility of acceptable limits of aflatoxins between China and other countries in Europe is another key factor to the exporting obstacle. To solve this problem, the contamination situation of aflatoxins in China is needed to be investigated, and the reasonable maximal limit of aflatoxins to be set up.In order to know the contamination situation of aflatoxins in peanuts of China, AFT concentration in peanuts sampling from twelve provinces were determined by immunoaffinity clean-up combined with high performance liquid chromatography and fluoresce detection. Statistic analysis was performed by Excel software. The technology of detoxification was also investigated in this study. The results were as follows:1. The optimal extraction conditions in the preparation of peanuts samples was that,5g peanut samples was extracted by15ml70%methanol under ultrasonic devices (power50W, temperature50℃) for5min and loaded onto the immunoaffinity column at a speed of1.5ml/min.2. The survey showed that AFT contamination was widespread in peanut of China in2009. The positive rates were as high as42.37%,22.40%,37.83%, and83.15%, respectively, in the peanut sampling from Northeast area, Northern area, Yangtze River area and Southern area. Statistical analysis of the survey results showed that there is no significant difference only between Yangtze River area and Northeast area(P>0.05), other areas have significant differences in positive rate between each other(P<0.01), AFT positive rate of the four areas from highest to lowest were:Southern area> Northeast area/Yangtze River area> Northern area; the AFB1positive rate of peanut indicated that, the result between Northeast area and Yangtze River area was significantly different (P<0.05), among other areas there were strong significant difference in positive rates (P<0.01), AFB1positive rates of four areas from highest to lowest were:Southern area> Yangtze River area> Northeast area> Northern area.3. Using EU peanut AFT limits as reference, over-limit rate was zero in Northeast peanut-producing area, while0.7%,9.29%and4.71%in peanut-producing areas of Northern, Yangtze River and South, respectively. Chi-square test results showed that the differences of AFT, AFB1over-limit rate of peanuts among the four areas were statistically significant. There was no significant difference between North area and Northeast area, as the same as South area and Yangtze River area (P>0.05), the over-limit rate was significantly different between Northeastern area and Yangtze River area, Northeastern area and Southern area, North area and Yangtze River area, North area and South area (P<0.01). According to the EU aflatoxins limits in peanuts, the over-limit rates of the four areas from highest to lowest were: Yangtze River area/Southern area were significantly higher than producing areas in Northeast/North area.4. The study on AFB1detoxification method of peanut showed that both ammonia and sodium hypochlorite have good effects. The higher concentration of the agents were, the better detoxification effect was, however, peanut flavor and color changed with larger concentration of the tested agents, and ammonia has less negative effect on peanut quality compared with sodium hypochlorite. Sodium hypochlorite is strongly oxidative, and harmful to crude fat and crude protein in peanuts. Based on the results, AFT of peanut can be reduced to zero almost by2%of ammonia or sodium hypochlorite. The quality of peanut can be significantly damaged if the concentration of sodium hypochlorite is over2%, although the peanut protein and fat content were less affected by ammonia while which can affect the color of the treated peanut. Therefore it was suggested that the appropriate concentration of these two detoxification agents were2%. |
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