Kinetics of ochratoxin a production and accumulation by Aspergillus carbonarius on synthetic grape medium at different temperature levels

The effects of incubation time (up to 10 d) and temperatures (7, 15, 20, 25, 30, 35, and 42 degrees C) on a mean ochratoxin A (OTA)-producing capacity and OTA accumulation by 4 Aspergillus carbonarius strains isolated from Spanish and Tunisian grapes were studied on grape-like medium. The limits of growth and OTA production have been identified. OTA production was significantly higher at 20 degrees C, followed by 25, 15, 30, 35 degrees C. No growth was observed at 7 degrees C and 42 degrees C after 10 d of incubation and, consequently, no OTA was detected at these temperature levels. In general, maximum mean OTA-producing capacity was found earlier with increasing incubation temperatures. However, at 35 degrees C, OTA was rarely detected although growth was maximum at this temperature. OTA accumulation was maximum after 10 d of incubation for all the temperatures except at 30 degrees C, were the maximum was detected at earlier incubation time (6 to 8 d) and then remained stable. Colony diameters and OTA accumulation along time were modeled by the Gompertz sigmoidal model and an estimation of maximum OTA accumulation rate and the delay until OTA production could be established. At high temperatures OTA accumulation starts earlier but increases slowly and becomes constant in a few days.