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Ochratoxin A (OTA) is a potent mycotoxin that can be found in grain crops, coffee, spices, and also grape musts and wines. OTA prevalence depends on the conditions (number of spores, humidity, and temperature) of the growing environment in which crops grow. OTA can be found in wines and musts and this is due to the fungal contamination of the grapes prior to wine making (Cecchini et al., 2006).

Building on previous research in wine making, Cecchini et al. (2006) designed a study to investigate if Saccharomyces and non-Saccharomyces yeast strains were involved in the reduction of OTA in both white must and red must. The authors crushed grapes (white or red) to musts; then added to these musts 2.0µg/l OTA. The musts were inoculated with pure pre-grown yeast cultures. Fermentation was at a controlled temperature of 20°C and was terminated after 36 days. Wine was separated from the yeast lees by centrifugation. OTA was performed by HPLC on the resulting wine, and on the methanolic extract of the yeast lees (MEL). This method allowed Cecchine et al. (2006) to determine where the OTA was: e.g. in the wine or in the yeast lees extract.

The authors found that OTA in the white wine was reduced by 46.8% to 52.2%, and in the red wine OTA was reduced between 53.2% and 70.1% across the different yeast strains. Cecchine’s et al. (2006) data showed that yeast in the red must had a higher capability in OTA reduction than the yeasts in the white must. In the red must, S. cerevisiae, S. byanus var. uvarum, S. bayanus, and Schiz. pombe showed a higher capacity in OTA reduction than the other yeasts (e.g. Candida pulcherima, Kloeckera apiculata, and Sach. Ludwigii).

The authors also found that a higher OTA content in the MEL from the red must wines, compared to the MEL from the white must. Cecchine et al. (2006) point out that a considerable amount of OTA was not recovered from either the wine or MEL. They, therefore, suggest that the OTA that was not recovered might be bound to the surface of the yeast cells (adsorption) and or that the MEL extraction of OTA was incomplete. The authors did not detect any OTA degradation products. Thus the authors suggest that OTA removal during the fermentation process might be a cell-binding (yeast) phenomenon (Cecchini et al., 2006).

Taken together, this research’s data showed OTA concentrations are reduced in both white and red musts during fermentation. The OTA reduction in red must is greater compared to the white must. Cecchini’s et al., (2006) research also demonstrated that some yeast strains showed higher OTA reducing capacity than others, and that OTA is likely to be bound to the cell walls of the yeast lees by adsorption.

Reference:

Cecchini, F. M. Morassut, E.G. Moruno, and R. Stefano. 2006. Influence of yeast strain on ochratoxin A content during fermentation of white and red must. Food Microbiology. 23:411-417.