Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2006
Publication Date: 9/1/2006
Citation: Whitaker, T.B., Slate, A.B., Jacobs, M., Hurley, M.J., Adams, J.G., Giesbrecht, F.G. 2006. Sampling almonds for aflatoxins; part i: estimation of uncertainty associated with sampling, sample preparation, and analysis. Journal of Association of Official Analytical Chemists International 89:1027-1034. Interpretive Summary: Aflatoxin is a carcinogenic and toxic compound produced by molds found in several agricultural commodities such as peanuts, cereals, and treenuts. Regulatory agencies world wide have established a maximum limit for aflatoxin in foods as a method to reduce aflatoxin contaminated foods. In the United States, the FDA has established a limit of 20 parts per billion total aflatoxin. As a result, almonds are inspected by exporters, importers, processors, and food manufacturers to detect and remove contaminated lots from the food chain. It is difficult to determine aflatoxin levels of large shipments or lots because of the errors associated with sampling, sample preparation, and analysis, collectively called the aflatoxin test procedure. Errors associated with the aflatoxin 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 aflatoxin in almonds were determined. Once the magnitude of the testing errors are know, 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 food manufacturers.
Technical Abstract: Domestic and international regulatory limits have been established for aflatoxin in almonds and other treenuts. It is difficult to get an accurate and precise estimate of the true aflatoxin concentration in a bulk lot due to the uncertainty associated with the sampling, sample preparation, and analytical steps associated with the aflatoxin test procedure. In order to evaluate the performance of aflatoxin sampling plans, the uncertainty associated with sampling lots of shelled almonds for aflatoxin was investigated. Twenty lots of shelled almonds were sampled for aflatoxin contamination. The total variance associated with measuring B1 and total aflatoxins in bulk almonds lots was estimated and partitioned into sampling, sample preparation, and analytical variance components. All variances were found to increase with an increase in aflatoxin concentration. Using regression analysis, mathematical expressions were developed to predict the relationship between each variance component (total, sampling, sample preparation, and analysis variances) and aflatoxin concentration. Variance estimates were the same for B1 and total aflatoxins. The mathematical relationships can be used to estimate each variance for a given sample size, subsample size, and number of analyses other than that measured in the study. Testing a lot with 15 ng/g total aflatoxin using a 10 kg sample, Vertical Cutter Mixer type mill, 100 g subsample, and high performance liquid chromatography analysis, the sampling, sample preparation, analytical, and total variances are 394.7 (CV=132.4%), 14.7 (CV=25.5%), 0.8 (CV=6.1%), and 410.2 (CV=135.0%, respectively. The percentage of the total variance for sampling, sample preparation, and analytical steps are 96.2, 3.6, and 0.2%, respectively.