Effect of Aspergillus carbonarius amounts on winemaking and ochratoxin A contamination

Aspergillus carbonarius is the major ochratoxin A (OTA)-producing fungus that contaminates wine grapes. To investigate the effect of the initial amount of A.carbonarius on winemaking and ochratoxin A contamination, different conidial concentrations of A.carbonarius were manually added to the grape musts before fermentation. Sampling was carried out at different stages in alcoholic fermentation, including crushing, maceration, pressing and alcoholic fermentation. The levels of alcohols, soluble solids, and reducing sugars in the musts were analyzed before and during the whole procedure of alcoholic fermentation. Aspergillus spp. and other fungal contaminants increased rapidly after crushing, however most died at 48h. OTA levels in the musts increased during the first 8-48h and then decreased sharply in A.carbonarius inoculants (1×10⁴ to 1×10⁶spores/g) in a spore concentration-dependent manner. Most OTA was retained in the pomaces fraction after the pressing operation. High amounts of A.carbonarius did not significantly affect yeast growth, sugar use, and alcoholic production during fermentation. In conclusion, high levels of contamination with A.carbonarius in the grape musts did not inhibit alcoholic fermentation, but caused high OTA residues in the wine produced.