Production of ochratoxin A by Aspergillus carbonarius on coffee cherries

Robusta coffee cherries collected before and during sun drying from two coffee farms in Thailand were examined for moulds producing ochratoxin A (OA). Aspergillus ochraceus was only detected in one sample, whereas Aspergillus carbonarius was isolated from 7 out of 14 samples. On gamma-irradiated coffee cherries, each of the six tested A. carbonarius strains produced OA. More than 4800 microg kg(-1) of toxin were detected under optimal conditions (25 degrees C, a(w) 0.99). OA production was strongly reduced (230 microg kg(-1)) at an a(w) of 0.94.