Ochratoxigenic fungi and ochratoxin A in cocoa during farm processing

Abstract

This study investigated the occurrence of fungi with the potential to produce ochratoxin A (OTA), and the occurrence of OTA, in Brazilian cocoa beans. Two hundred and twenty two samples of cocoa were evaluated, taken at various stages of fermentation, drying and storage. Samples were collected from Bahia, the main cocoa producing region in Brazil. Fungi with the potential to produce OTA were isolated by direct plating of cocoa beans on Dichloran 18% Glycerol agar after surface disinfection, and identified by standard techniques. The ability of the fungi to produce OTA was estimated using the agar plug technique and TLC. The presence of OTA in cocoa samples was determined by HPLC after immunoaffinity column clean up. The most common ochratoxigenic species found were Aspergillus carbonarius and A. niger aggregate, with lower numbers of A. melleus, A. westerdijkiae and Av. ochraceus. A considerable increase in the numbers of these species was observed during drying and storage. OTA was found at all stages of cocoa processing, with the major incidence during drying and storage. The OTA levels found were in general low and there was a strong positive correlation between the presence of A. carbonarius and OTA contamination in the beans.