Growth and ochratoxin A production by Aspergillus carbonarius at different pHs and grape maturation stages

Aims: The objective of this work was to study the effect of some factors, linked to grape composition during ripeness process, on the growth and ochratoxin A (OTA) production of Aspergillus carbonarius isolated from grapes. Methods and Results: Aspergillus carbonarius isolates were tested (i) in vitro, in Czapek yeast autolysate agar (CYA) at different pHs (2·5–4·5) and incubation times (2–6 days), and (ii) in situ, in fresh grapes collected at different maturation stages. Aspergillus carbonarius was able to grow with the same intensity at the different maturation stages and pH levels tested. In general, a similar trend of OTA production by A. carbonarius in response to acidity in media and in grape was observed. Low pH level seemed optimal for maximum OTA production. Conclusions: Aspergillus carbonarius strains can strongly grow and produce OTA on grape from the early stages of maturation. Extrinsic environmental conditions at the harvest period and skin thickness are, probably, the mains factors contributing to OTA contamination of grapes at the end of maturation. Significance and Impact of the Study: The results lead to a better understanding of the critical point during grape maturation for the growth of ochratoxigenic fungi and the toxin production.