An overview of ochratoxin A in beer and wine

Ochratoxin A (OTA) is a mycotoxin produced mainly by several fungal species of the genera Aspergillus and Penicillium. This mycotoxin has been shown to be nephrotoxic, hepatotoxic, teratogenic and carcinogenic to animals and has been classified as a possible carcinogen to humans. OTA occurs in a variety of foods, including beer and wine. Reports on OTA occurrence in beer indicate that this is a worldwide problem due to the widespread consumption of this beverage. At present, the European Union (EU) has not set a maximum allowable limit (MAL) for this mycotoxin in beer, although there is a limit in barley and malt. Studies carried out in different countries agree in the high proportion of samples contaminated with OTA although levels are, usually, below 0.2 ng/ml. OTA occurrence has been related to the contamination of malt barley with ochratoxigenic species, particularly Penicillium verrucosum. OTA produced in grains is carried to wort and, although fermentation decreases the concentration, the toxin is not eliminated. Reducing the fungal contamination of malt barley is the most promising strategy for reducing OTA in beer. With regard to wine, surveys on the presence of OTA have been conducted worldwide. The proportion of wines in which OTA is detected is very high (above 50%) in some countries (especially in the Mediterranean basin) although only a few wines contained concentrations exceeding the MAL laid down by the EU (2.0 ng/ml). A gradient of concentration is usually recognized; OTA levels decrease in the order red, rosé, and white wine but also with increasing latitude of the producing countries. OTA presence in wines is due to the black aspergilli, mainly A. carbonarius, which can grow on grapes in the vineyards and produce the toxin. At grape crushing, the juice can be contaminated with the toxin which is carried over into wine, where it persists due to its stability. Pre- and post-harvest treatments are being investigated to diminish contamination of wines as much as possible.