Mycelial growth and ochratoxin A production by Aspergillus section Nigri on simulated grape medium in modified...

To evaluate the impact of modified atmosphere packaging on in vitro growth of Aspergillus carbonarius and Aspergillus niger, and possible effects on ochratoxin A (OTA) biosynthesis.

Ochratoxigenic isolates belonging to the species A. carbonarius and A. niger were grown on a synthetic grapejuice medium (SNM) and packaged in combinations of controlled O(2) (1% and 5%) and CO(2) levels (0% and 15%), and in air as a control. Colony diameters were recorded every 3 days up to 21 days, and OTA was analysed after 7, 14 and 21 days. The greatest reductions in mycelial growth rate were observed at 1% O(2) followed by 1% O(2)/15% CO(2), whereas 5% O(2) stimulated the growth of all isolates. OTA production by A. carbonarius and A. niger isolates was minimized at 1% O(2)/15% CO(2) and 1% O(2), respectively, after 7 days of incubation. Maximal OTA accumulation after 7 days was observed for all isolates in the control pack and at 5% O(2).

Of the atmospheres tested, only 1% O(2) combined with 15% CO(2) consistently reduced fungal growth and OTA synthesis by A. carbonarius and A. niger.

Storage under modified atmospheres is unlikely to be suitable as the sole method for OTA minimization and grape preservation; other inhibitory factors are necessary.