The effect of juice clarification, static or rotary fermentation and fining on ochratoxin A in wine

Semillon and Shiraz grapes containing ochratoxin A (OA) were produced by inoculation of bunches on the vine with Aspergillus carbonarius. Small scale vinification of these grapes was performed and the OA content at various stages was analysed. Semillon must was treated with pectolytic enzymes and the juice after pressing was fined with bentonite. Neither pectolytic enzymes nor bentonite influenced the OA content of the clarified juice. Shiraz must was vinified by either static or rotary fermentation. No differences in the OA content of wine after pressing were noted. OA was concentrated in juice lees and gross lees. However, additional juice or wine recovered from lees after centrifugation did not display increased OA contamination compared to racked juice or wine. Addition of bentonite at 2.5 g/L to a Semillon wine containing 56 mg grape-derived protein/L and ca. 8 μg OA/kg resulted in a 67% reduction in OA concentration. Potassium caseinate showed some effect, whereas gelatin, isinglass and PVPP did not significantly diminish OA in white wine compared to wine settled without fining agents. Addition of yeast hulls at 5.0 g/L to a Shiraz wine containing ca. 5 μg OA/kg yielded a 43% reduction. Gelatin was also slightly effective. Storage of wine for 10–14 months resulted in a decrease in OA concentration of 22% and 29% for white and red wines, respectively.