Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2002
Publication Date: 12/31/2002
Citation: Dorner, J.W. 2002. Simultaneous quantification of aspergillus flavus/a. parasiticus and aflatoxins in peanuts. Journal of Association of Official Analytical Chemists International.
Interpretive Summary: Aflatoxin contamination of peanuts is a serious economic problem for peanut producers and processors and a food safety concern for consumers around the world. Contamination, which results from growth in peanuts by the molds, Aspergillus flavus and A. parasiticus, can occur in the field under drought conditions or in storage when peanuts are not maintained at safe moisture levels. A method was developed that enables the simultaneous determination of the amounts of A. flavus/A. parasiticus and aflatoxin in the same sample of peanuts. A peanut-water slurry is produced by grinding an equal weight of peanuts with water in a vertical cutter mixer for 7 minutes. Separate subsamples are taken for (1) dilution plating to determine A. flavus and A. parasiticus colony forming units per gram of peanuts and (2) liquid chromatographic analysis to quantify aflatoxin. In producing the slurry, it is necessary to ensure that the temperature does not exceed 45ø C, or fungi will be killed. The method was used in the analysis of 60 peanut samples from crop year 1999, and analysis of the data showed a significant positive correlation between the amounts of A. flavus/A. parasiticus and aflatoxin. The method provides a much better indication of the relationship between A. flavus/A. parasiticus and aflatoxin in peanuts than traditional methods of plating individual seeds to determine percent seeds infected by the fungi.
Technical Abstract: A method was developed for simultaneous quantification of Aspergillus flavus/A. parasiticus and aflatoxins in peanuts. Peanut samples were ground with an equal weight of water in a vertical cutter mixer to produce a slurry. Separate subsamples were taken for dilution plating to determine total colony forming units (CFU)/g of A. flavus/A. parasiticus and for LC analysis to determine aflatoxin concentrations. Dry-grinding peanuts for homogenization of aflatoxins produced high temperatures that killed most of the A. flavus/A. parasiticus propagules. Addition of water to produce a slurry kept the temperature from rising above levels which killed the fungi. A 7-min grind time provided optimal homogenization for both the fungi and aflatoxins, so long as the temperature of the slurry did not exceed 45ø C. In the analysis of 60 shelled peanut samples, total aflatoxin concentrations ranged from 0 to 10,000 ng/g and total A. flavus/A. parasiticus ranged from 1.4 103 to 3.2 106 CFU/g. Regression analysis showed a significant positive correlation (P < 0.0001) between the quantities of A. flavus/A. parasiticus and aflatoxin (R2 = 0.82).