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United States Department of Agriculture

Agricultural Research Service


item Vargas, Eugenia
item Whitaker, Thomas
item Dos Santos, Eliene
item Slate, Andrew
item Lima, Francisco
item Alves Franca, Regina

Submitted to: Journal of the Association of Official Analytical Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2003
Publication Date: 7/15/2004
Citation: Vargas, E.A., Whitaker, T.B., Santos, E.A., Slate, A.B., Lima, F.B., and Franca, R.A. Testing green coffee for ochratoxin A, Part I: Estimationof Variance Components. Journal of Association of Official Analytical Chemists, Int., 87:943-949. 2004

Interpretive Summary: Ochratoxin is a carcinogenic and toxic compound produced by molds found in coffee, wine, and other agricultural commodities. The U.S. Food and Drug Administration is considering the establishment of an advisory or legal limit that would control the maximum quantity of ochratoxin allowed in coffee imported into the United States. As a result, coffee beans are inspected by exporters, importers, processors, and manufacturers to detect and remove contaminated lots from the food chain. It is difficult to determine the ochratoxin level of large shipments or lots because of the errors associated with sampling, sample preparation, and analysis, collectively called the ochratoxin test procedure. Errors in the test procedure results in some lots being mis-classified. Some of the good lots test bad and some of the bad lots test good. The errors associated with measuring ochratoxin in coffee beans were determined. Once the magnitude of the testing errors are known, methods can be developed to reduce the testing errors which will reduce the number of lots mis-classified. This will reduce both health risks to the consumer and economic loss to importers, processors, and manufacturers.

Technical Abstract: The variability associated with testing lots of green coffee beans for ochratoxin A was investigated in this study. Twenty-five lots of green coffee were tested for ochratoxin A contamination. The total variance associated with testing green coffee was estimated and partitioned into sampling, sample preparation, and analytical variances. All variances were found to increase with an increase in ochratoxin A concentration. Using regression analysis, mathematical expressions were developed to model the relationship between ochratoxin A 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 ochratoxin A concentration. Testing a lot with 5 ng/g ochratoxin A using a 1-kg sample, Romer RAS mill, 25-g subsamples, and high performance liquid chromatography analysis, the total, sampling, sample preparation, and analytical variances were 10.75 (CV=65.6%), 7.80 (CV=55.8%), 2.84 (CV=33.7%), and 0.11 (CV=6.6%), respectively. The percentages of the total variance for sampling, sample preparation, and analytical were 73, 26, and 1%, respectively.

Last Modified: 06/22/2017
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