Submitted to: Journal of the Association of Official Analytical Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2005
Publication Date: 10/1/2006
Citation: Vargas, E.A., Whitaker, T.B., Santos, E.A., Slate, A.B., Lima, F.B., Franca, R.C. 2006. Testing green coffee for ochratoxin a, part iii: performance of ochratoxin a sampling plans. Journal of the Association of Official Analytical Chemists 89:1021-1026. 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. 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: Green coffee shipments are often inspected for ochratoxin A (OTA) and classified into good or bad categories depending on whether the OTA estimates are above or below a defined regulatory limit. Because of the uncertainty associated with the sampling, sample preparation, and analytical steps of an OTA test procedure, some shipments of green coffee will be misclassified. The misclassification of lots lead to some good lots being rejected (sellers’ risk) and some bad lots being accepted (buyers’ risk) by an OTA sampling plan. Reducing the uncertainty of an OTA test procedure and using an accept/reject limit less than the regulatory limit can reduce the magnitude of one or both risks. The uncertainty of the OTA test procedure is most effectively reduced by increasing sample size (or increasing the number of samples analyzed for OTA), since the sampling step is the largest source of uncertainty in the OTA test procedure. The effects of increasing sample size and changing the sample accept/reject limit relative to the regulatory limit on the performance of nine OTA sampling plans for green coffee were investigated. For a given accept/reject limit of 5 microgram/kilogram, increasing sample size increased the percentage of lots accepted at concentrations below the regulatory limit and increased the percentage of lots rejected at concentrations above the regulatory limit. As a result, increasing sample size reduced both the number of good lots rejected (sellers’ risk) and the number of bad lots accepted (buyers’ risk). For a given sample size (1 kilogram), decreasing the sample accept/reject limit from 5 to 2 microgran/kilogram relative to a fixed regulatory limit of 5 microgram/kilogram decreased the percentage of lots accepted and increased the percentage of lots rejected at all OTA concentrations. As a result, decreasing the accept/reject limit below the regulatory limit increases the number of good lots rejected (sellers’ risk), but decreases the number of bad lots accepted (buyers’ risk).