Mycotoxins are toxic compounds produced by fungi (mushrooms, molds, yeast, etc.). The specific nature and toxicity of mycotoxins vary along with the source organism. Generally, they are secondary metabolites produced in very limited quantities if all by a given species, but spoilage can be a problem in both animal and human food.
The genus Aspergillus is rich in mycotoxin producing species. The United States already has legal limits on the presence of Aflatoxin (a liver toxin made by Aspergillus flavus and Aspergillus parasiticus) in cereal and nut crops, products like peanut butter must be tested before sale is allowed. Recently, Ochratoxin A has been identified as a concern in Europe affecting multiple food industries including poultry, grains, and certain fruit products including wine. Ochratoxin A is produced by Aspergillus carbonarius, Aspergillus nigri and certain Penicillium species; it affects kidney function and has been identified as a potential carcinogen. In May of 2006 the European Union (EU) Committee amended an earlier decision setting a new maximum level of OTA in wine to 2 parts per billion. Beginning with 2005 vintages, all wine either produced in or imported to the EU must now be below the threshold to be sold legally. This means that if your winery exports product to any EU member nation it will need to be assayed for Ochratoxin A (OTA).
Little is known about the presence of OTA in American wine, but as with all mycotoxins presence or absence is a function of the fungi that produce them. In European studies, contamination can occur in the field or during transport and storage. Not surprisingly, OTA contamination tends to be more prevalent in products made in humid areas and/or from unsound fruit. Poor field or cellar sanitation can contribute to the risk of contamination. Because the fungus grows on the exterior surfaces of the fruit, the concentration of OTA, when present, tends to be higher in red wines than whites or rosés due to the increased skin contact necessary to extract pigments and tannins. OTA concentration in wine tends to peak after maceration and declines somewhat during fermentation due to yeast adsorption. Fining with either protein or activated charcoal has been shown to reduce OTA concentration in wine and juice products.
There are several methods available to monitor OTA, including enzyme linked immuno-sorbent assays (ELISA) developed for other food industries that are available for quickly measuring the compound in a semi-quantitative fashion. If the ELISA generates a measurement approximate to threshold limits, more precise (and more expensive) means can be used to pin down the quantity of OTA present. These methods include high performance liquid chromatography, quantitative ELISA or the potential use of electronic biosensors. Currently there are several wine laboratories offering OTA analysis, cost start around $200 per sample.
If you do not export to Europe, the EU’s new legal limits are not as relevant but let this be a gentle reminder to use best practices (vineyard care, sorting and clean cellars) to prevent the introduction of unwanted components to your wine.
Web URLS for more information about ochratoxins
Links for information about commercial labs that offer analysis
Castellari, M., A. Versari, A. Fabiani, G.P. Parpinello, and S. Galassi. 2001. Removal of ochratoxin A in red wines by means of adsorption treatments with commercial fining agents. J. Agric. Food Chem. 49:3917-3921.
Gambuti, A., D. Strollo, A.Genovese, M. Ugliano, A. Ritieni, and L. Moio 2005. Influence of enological practices on ochratoxin a concentration in wine. American Journal of Enology and Viticulture 56:155
Zimmerli, B., and R. Dick. 1996. Ochratoxin A in table wine and grape-juice: Occurrence and risk assessment. Food Addit. Cont. 6:655-668.