Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2004
Publication Date: 7/25/2004
Citation: Park, D.L., Whitaker, T.B., Simonson, J., Morris, H.F., Durr, B., Njapau, H. 2004. Evaluation of sample collection, preparation, and analytical procedures used to estimate aflatoxin in shelled corn in louisiana in 1998 . Journal of Association of Official Analytical Chemists International vol. 87, No. 4. Interpretive Summary: Aflatoxin is a naturally occurring toxic and carcinogenic compound produced by fungi and found on many types of grains. The FDA has established a maximum limit for aflatoxin levels in consumer foods and animal feeds. As a result, the grain industry works closely with state and federal regulatory agencies to inspect grain at a buying point in an attempt to detect and remove contaminated grain from the food and feed supply. For both economic and food safety reasons, it is important to use accurate and precise methods to measure aflatoxin in bulk lots sold to elevator operators at the buying point so that lots can be correctly classified as acceptable or unacceptable. The precision associated with the aflatoxin test procedure (sampling, sample preparation, and analysis) used at grain elevators was measured. Sampling was shown to be the largest source of variability in the aflatoxin test procedure. Results indicate that increasing sampling size would be a cost effective method to reduce sampling error. Analytical methods used by elevator operators under field conditions were compared to analytical methods used in state laboratories under controlled conditions. Elevator laboratories tended to measure less aflatoxin than state laboratories. These results indicate that (1) some contaminated lots above the FDA maximum limit may be making their way into the food and feed supply, and (2) elevator operators should review their lab procedures and training methods to improve the accuracy of their analytical methods.
Technical Abstract: The inherent difficulty in accurately determining the true aflatoxin concentration of a lot of corn may have serious implications. Deviations from the true value are of even greater significance at busy locations where a high throughput is desired. This study was instituted to measure the variability in aflatoxin test results, associated with sampling, sample preparation, and analysis of shelled corn at such locations. One hundred lots of shelled corn from 10 elevators in Louisiana were analyzed for aflatoxin using the Aflatest method (at elevators and the laboratory) and high-pressure liquid chromatography (laboratory only). Mean aflatoxin levels determined at 4/9 elevators were significantly (p<0.05) different from those obtained in the laboratory using the Aflatest method. Differences may be due to minimal training of the analyst and/or substandard laboratory conditions Overall, Aflatest method results were lower than those obtained by HPLC. The total variances associated with both analytical methods were not substantially different and more a function of variability associated with sampling and sample preparation. Since samples were apportioned after sampling but prior to sample preparation, most of the variance observed in the study could be attributed to sampling, which is the largest contributor to errors in estimating the true value of aflatoxin in bulk lots of corn.