Effect of sulfur dioxide and ethanol concentration on fungal profile and ochratoxin a production by Aspergillus carbonarius during wine making

Fungal profiles and ochratoxin A (OTA) accumulation during wine making were investigated using five different wine grape cultivars, Cabernet Sauvignon, Pinot Noir, Merlot, Syrah and Petit Verdot and the intrinsic influences caused by sulfur dioxide, ethanol and combine effect of ethanol and reducing sugar were analyzed using Cabernet Sauvignon and inoculation of Aspergillus carbonarius. Aspergillus spp. and Penicillium spp. were found as the major fungi in all winemaking processes and were highly correlated with OTA accumulation in wine. Most fungi died and OTA production decreased after 48h of alcoholic fermentation, being consistent with the period when ethanol accumulation increased. The addition of SO₂ significantly inhibited the growth and OTA production of A.carbonarius with complete inhibition at 500mg/L. When the ethanol concentration in the must increased to the range of 2-4%, growth and OTA production of A.carbonarius were significantly inhibited. Reducing sugar concentration had no significant effect on the growth and OTA production of A.carbonarius within the levels changing during the winemaking. Therefore, the increase of ethanol concentration played an important role in causing the decrease of fungal contamination and OTA accumulation during winemaking.