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United States Department of Agriculture

Agricultural Research Service

Title: Testing Shelled Corn for Aflatoxin, Part I: Estimation of Variance Components

Authors
item Johansson, Anders
item Whitaker, Thomas
item Hagler, Jr, Winston - NC STATE UNIVERSITY
item Giesbrecht, Francis - NC STATE UNIVERSITY
item Young, James - NC STATE UNIVERSITY

Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 9, 2000
Publication Date: September 1, 2000
Citation: JOHANSSON, A.S., WHITAKER, T.B., HAGLER, JR, W.M., GIESBRECHT, F.G., YOUNG, J.H. TESTING SHELLED CORN FOR AFLATOXIN, PART I: ESTIMATION OF VARIANCE COMPONENTS. JOURNAL OF ASSOCIATION OF OFFICIAL ANALYTICAL CHEMISTS INTERNATIONAL. 2000. v. 83. p. 1264-1269.

Interpretive Summary: Aflatoxin is a carcinogenic and toxic compound produced by molds found in several grains. The Food and Drug Administration has established legal limits that control the maximum quantity of aflatoxin allowed in food and feed products. As a result, grain products are inspected by processors, manufacturers, and USDA to detect and remove contaminated lots from the food and feed chain. It is difficult to determine the aflatoxin level of large shipments or lots because of the errors associated with sampling, sample preparation, and analysis, collectively called the aflatoxin test procedure. Errors in the test procedure result in some lots being miss-classified. Some of the good lots test bad and some of the bad lots test good. The errors associated with measuring aflatoxin in shelled corn were determined. Once the magnitude of the testing errors are known, methods can be developed to reduce the testing errors which will reduce the enumber of lots miss-classified. This will reduce both health risks to the consumer and economic loss to the grain industry.

Technical Abstract: The variability associated with testing lots of shelled corn for aflatoxin was investigated. Eighteen lots of shelled corn were tested for aflatoxin contamination. The total variance associated with testing shelled corn was estimated and partitioned into sampling, sample preparation, and analytical variances. All variances were found to increase with an increase in aflatoxin concentration. Using regression analysis, mathematical expressions were developed to model the relationship between aflatoxin concentration and the total, sampling, sample preparation, and analytical variances. The expressions for these relationships were used to estimate the variance for any sample size, subsample size, and number of analyses for a specific aflatoxin concentration. Testing a lot with 20 parts per billion (ppb) aflatoxin using a 1.13-kg sample, Romer mill, 50-g subsamples, and high performance liquid chromatography analysis, the total, ,sampling, sample preparation, and analytical variances are 274.9 (CV=82.9%), 214.0 (CV=73.1%), 56.3 (CV=37.5%), and 4.6 (CV=10.7%), respectively. The sampling, sample preparation, and analytical steps account for 77.8, 20.5, and 1.7%, of the total aflatoxin testing variability, respectively.

Last Modified: 7/28/2014
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