Effect of water activity and temperature on growth ofAspergillus carbonarius andAspergillus tubingensis and their interactions on ochratoxin A production

Abstract

Aspergillus section Nigri are described as the main source of ochratoxin A (OTA) contamination in grapes and wine worldwide. The grape-growing area in Argentina has a wide latitudinal extension with ecological variations that allow the classification of well-demarcated regions. The aims of this study were: to determine the effect of eco-physiological parameters on growth of Aspergillus tubingensis and Aspergillus carbonarius and to evaluate the interaction between these species on OTA production in synthetic grape juice medium under different water activity (a w ) and temperature conditions. The results showed that optimal growth conditions for A. tubingensis and A. carbonarius were 0.980 a w and 28 °C, however A. tubingensis grew faster than A. carbonarius at all temperatures and a w tested. OTA production by A. carbonarius was favoured at 20 °C and 0.950-0.965 a w , during 14 days of incubation. The effect of A. tubingensis on OTA production by A. carbonarius was mainly dependent on temperature. At 35 °C, A. tubingensis reduced the OTA production while this effect was not observed at 20 °C. More OTA could be produced as a defence reaction against fungal competitors to maintain niche colonisation, but in this study no effects by a related species were observed.