Mixed-effects models and tolerance limits for mycotoxin measurements in food-stock lots
We describe mixed-effects models for aflatoxin measurements that were obtained from a set of incoming grain-delivery trucks at a pet food processing facility in Southeast Asia. Aflatoxin belongs to a group of highly toxic substances known as mycotoxins, the presence of which in food stocks is a major food safety concern around the world. The modeling objective is to evaluate the inter-truck and intra-truck variance components, and to estimate the influence of various factors on the measurements. These factors include, for example, the grain quality metrics from the individual suppliers, and the sample preparation and analytical processes used in the specific measurement protocols. Furthermore, we provide a brief description of how the modeling results can be used to obtain appropriate estimates for the one-sided tolerance limits, and, thereby, to evaluate the overall risk of high aflatoxin levels in the incoming truck lots.