Comparing the performance of sampling plans that use a single regulatory limit based upon total aflatoxins to sampling plans that use dual limits based upon B1 and total aflatoxins

The European Commission (EC) aflatoxin sampling plan for ready-to-eat tree nuts such as almonds requires that each of the three 10 kg laboratory samples must all test less than 2 ng/g aflatoxin B-1 (AFB(1)) and 4 ng/g total aflatoxins (AFT) for the lot to be accepted. Exporters have observed that the AFB(1)/AFT ratio varied greatly from sample to sample and the ratio appeared to average more than 50%. Because of the concern that dual limits associated with the EC aflatoxin sampling plans may reject more lots than similar sampling plans that use a single limit based upon total aflatoxins, studies were designed with the objectives to (a) measure the distribution of AFB(1)AFT ratio values using sample test results associated with testing U.S. almond lots exported to the European Union; (b) use Monte Carlo methods to develop a model to compute the effects of using dual limits based upon AFB(1), and AFT on the probability of accepting almond lots; and (c) compare the probability of accepting almond lots using the current Codex aflatoxin sampling plans for tree nuts when using single limits versus the use of dual limits. The study results showed that the mean and median among 3,257 AFB(1)/AFT ratio values was 87.6% and 91.9%, respectively, indicating that the distribution among the ratio values was negatively skewed. Only 31% of the 3,257 AFB(1)/AFT ratio values are less than the mean ratio of 87.6%. Codex aflatoxin sampling plans for tree nuts using a single limit based upon total aflatoxins had the highest probability of accepting lots at all lot concentrations when compared to the probability of accepting lots with dual limits. As the AFB(1) limit decreased from 90 to 50% of the total limit, the probability of rejecting lots at all concentrations increased when compared to the Codex aflatoxin sampling plans with a single limit based upon total aflatoxins.