Submitted to: Journal of Food Additives & Contaminants
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/17/2005
Publication Date: 12/10/2005
Citation: Vargas, E.A., Whitaker, T.B., Santos, E.A., Slate, A.B., Lima, F.B., Framca, R.C. 2005. Design of sampling plans to detict ochratoxin a in green coffee. Journal of Food Additives & Contaminants. Interpretive Summary: Ochratoxin A (OTA) is a carcinogenic and toxic compound produced by molds found in coffee, wine, grains, and other agricultural commodities. The Food and Drug Administration and the European Union are considering the establishment of an advisory or legal limit that would control the maximum quantity of OTA allowed in coffee imported into the United States and Europe. As a result, processors, exporters, importers, food manufacturers, and regulatory agencies inspect coffee bean lots to detect and remove contaminated lots from the food chain. It is difficult to accurately determine the true OTA level of large shipments because of the errors associated with the test procedure used to quantify OTA in bulk shipments and as a result the inspection program will misclassify some lots. Some of the good lots test bad and some of the bad lots test good. The uncertainty and distribution among sample test results was measured. Using the uncertainty and distribution measurements, a method was developed to evaluate how many coffee lots an OTA sampling plan will misclassify and predict the health risk to buyers and the economic risk to sellers. Examples of OTA sampling plans were presented to demonstrate how to design sampling plans to reduce misclassification of coffee lots. Increasing sample size is the most effective way to reduce both health risks to the consumer and economic loss to exporters, importers, processors, and manufacturers.
Technical Abstract: The establishment of maximum limits for ochratoxin A (OTA) in coffee by importing countries requires that coffee producing countries develop scientifically based sampling plans for export coffee that will meet mycotoxin regulation requirements. A study was carried out to design an official sampling plan to determine OTA in green coffee produced in Brazil. Twenty-five lots of green coffee were sampled according to an experimental protocol where 16 test samples were taken from each lot resulting in a total of 800 OTA analyses. 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, assuming a regulatory limit of 5 microgram/kilogram ochratoxin A and using a 1 kilogram sample, Romer RAS mill, 25 gram subsamples, and high performance liquid chromatography. The observed OTA distribution among the 16 OTA sample results was compared to several theoretical distributions. The 2 parameter-log normal distribution was selected to model ochratoxin A test results for green coffee as it gave the best fit across all 25 lot distributions. Specific computer software was developed using the variance and distribution information to predict the probability of accepting or rejecting coffee lots at specific OTA concentrations. The acceptation probability was used to compute an operating characteristic (OC) curve specific to a sampling plan design. The OC curve was used to predict the rejection of good lots (sellers’ or exporters’ risk) and the acceptance of bad lots (buyers’ or importers’ risk).