Predicting noncompliant levels of ochratoxin A in cereal grain from Penicillium verrucosum counts

Aims: To model the probability of exceeding the European legislative limit of 5 mug ochratoxin A (OTA) per kilogram grain in relation to Penicillium verrucosum levels and storage conditions, and to evaluate the possibilities of using P. verrucosum colony counts for predicting noncompliant OTA levels. Methods and Results: Cereal samples were inoculated with P. verrucosum spores and stored for up to 9 months at temperatures and water activities ranging from 10-25degreesC and a(w) 0.77-0.95. A logistic regression analysis showed that the probability of exceeding 5 mug OTA kg(-1) grain was related to colony counts of P. verrucosum and water activity. The sensitivity and specificity of various P. verrucosum count thresholds for predicting noncompliant OTA levels were estimated, using data from the storage trial and natural cereal samples. Conclusion: The risk of exceeding 5 mug OTA kg(-1) grain increased with increasing levels of P. verrucosum, and with increasing water activities. A threshold of 1000 CFU P. verrucosum per gram grain is suggested to predict whether or not the legislative limit is exceeded. Significance and Impact of the Study: This study has provided a tool to evaluate the levels of P. verrucosum in grain in relation to OTA levels. Hence, mycological analyses can be used to identify cereal samples with high risk of containing OTA levels above the legislative limit.