Influence of water activity on physical properties, fungal growth, and ochratoxin A production in dry cherries and green-coffee beans

Water activity (a(w)) influences the growth of fungi as well as the biosynthesis of ochratoxin A (OTA). The objective of this study was to obtain the critical storage conditions at which coffee beans are not susceptible to deteriorative physical changes and quantification of OTA in dry cherries and green-coffee beans after 60 days of storage at 35 degrees C. a(w) significantly affected the color, texture, and morphology in dry cherries and in green-coffee beans after storing. Three different genera of fungi were isolated from coffee samples, Aspergillus, Rhizopus, and Penicillium. The analyzed coffee beans showed a high concentration of OTA (15.49-65.22 mu g center dot kg(-1)). The conditions at 35 degrees C under which the physical changes and the highest concentration of OTA were found are the following: a(w) between 0.515 and 0.821. These results suggest that the control of a(w) during coffee bean storage can be useful to limit OTA formation, whereas the physical properties are maintained. Novelty impact statement Dry cherries showed higher OTA content than green-coffee beans. In addition, water activity affects the OTA content, color, texture, and morphology in dry cherries and green-coffee beans. Thus, the control of water activity during coffee bean storage can be useful to limit OTA formation.