| Aflatoxin BI is a second metabolin of Aspergillus flavus and A. parasittcus. It is seriouspoisonous to human health and widely exists in various foods. Aflatoxin B (AFBi) has becomeone of the most important testing items in world trades. The Chinese Bureau of Technologyand Supervisor has formulated the market entering rule of AFBi in trades of rice, flour, edibleoil, soy sauce, and vinegar. However, the traditional testing methods could not satisfy thecurrent market in detecting AFBi in goods. Considering to the above facts, this article studiedand evaluated the application of ELISA in tests of AFBi in foods. Some factors that couldbring errors to results were also analyzed. The results would provide some useful informationto the application of ELISA in control of food safety and performance of detecting works. It was found that ELISA was a feasible way to detect of AFBi in food products. Somecontrol parameters in quantitative analysis of ELISA were established. The results certified thefeasibility of ELISA in detection of AFBi in agricultural products. ELISA showed linear rangeof O.lug/kg~10(j.g/kg, sensitivity of 0.lug/kg, and variation coefficient between batches of lessthan 4%. In range of O.lug/kg~10|ag/kg, the average recover rate of standard was 92.74%. Therelativity coefficient (R2) of the results obtained by ELISA was 0.9785, and the linear slopewas 1.0524. The results obtained by ELISA was consistent with that by TLC. The effect ofsubstrates in sample on the detecting results of AFBi was rice< corn < peanut. Compared withstandard AFBi solution, all samples had some kind of non-specific interferential influence onthe results. The influence decreased with the increase of dilution fold. Dilution fold of 5 couldsatisfy the testing requirements in rice. Rice was used as raw material to study the effects of different extract solvents on the resultsin detail, and the effect of ultrasonic wave on sample extraction. The ratio of solvent to solidsubstrates was optimized. Feasible extraction parameters were achieved in rapid treatments ofultrasonic wave. By this way, the accuracy and testing speed of ELISA were improved. Thehighest extraction efficiency was achieved in water solution of 50% acetone (v/v) and 50%methanol, which was independent of the contamination degree of rice. The recovery degree ofstandard was 80.4%~140% in level of 0.lug/kg, lug/kg, and lOug/kg. The method showedgood repetition and stability with relative deviation of 2.99%~9.61%. The extraction periodwas shortened, and extraction efficiency was improved greatly bycombining treatment of ultrasonic wave and water solution of 50% methanol (v/v). Theextraction efficiency reached to the maximum point 10 minutes later in ultrasonic wavetreatments, which was much faster than that in traditional vibration treatments (30 minuteslater). Moreover, the maximum density of extraction was increased 30.5% with ultrasonicwave treatment. The recover ratio of standard was 83.0-95.2% at adding le^?5 of 0.1,1, andlO^g/kg, which was about 10% higher than that under vibration treatment. The frequency ofultrasonic wave had no significant effect on detecting results. Effects of pH, salt density and metal ions (Fe, Cu, Pb> As) on the testing results ofELISA were also studied. The influence of these factors was certified in the results. However,these effects could be diminished when the extraction was leached with certainsolvents before testing. The results would provide theory information to the foundation ofextraction methods of AFBi in different food samples. According to the results, it wassuggested ? samples of high salt contents, such as soy sauce, should be removed of salt firstlyand extracted with chloroform before testing; ?edible oil should be degreased before testing,that is it should be solved with petroleum ether and extracted with methanol after that; ?variouscatsups, for example soy peppery catsup, should be removed of salt and degreased; ?vinegar... |
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