The mycotoxin contamination of agricultural products is a serious health hazard which has received increasing attention worldwide. Ochratoxin A (OTA) is one of the most common naturally occurring mycotoxins and it is receiving increasing attention for its toxic effects, high incidence in a wide range of food commodities, and widespread exposure in healthy humans. It is classified as a possible human renal carcinogen (group 2B) by the International Agency for Research on Cancer (IARC).

In the European diet, wine has been identified as the second major source of human exposure to OTA, following cereals. Until recently, the source of OTA contamination in grapes was unknown. Our work provides a strong evidence of the contribution of the main fungal species involved in this contamination.

Our paper describes the mycobiota of grapes belonging to representative wine regions, located mainly along the Mediterranean coast of Spain, at different developmental stages of the grape. Although the possible participation of different OTA-producing species may occur, our results show strong evidence of the contribution of Aspergillus carbonarius in the OTA contamination in grapes, mainly at the last developmental stage of the berries, and consequently in wine. This is supported not only by its important role in the mycobiota of grapes, but also by the extremely high ability to produce OTA and the scarce or null contribution of the typical OTA-producing species Aspergillus ochraceus and Penicillium verrucosum.

Mycotoxins are fungal secondary metabolites that can cause different alterations and pathological conditions in humans and animals. OTA is a nephrotoxic mycotoxin naturally found in a wide range of foods. OTA contamination of food was, until recently, believed to be produced mainly by Aspergillus ochraceus and by Penicillium verrucosum, which affect mainly dried stored foods and cereals respectively, in different regions of the world.

However, recent surveys have clearly shown that some species belonging to the black aspergilli, such as Aspergillus niger and Aspergillus carbonarius, are sources of OTA in food commodities such as wine, grapes, and dried vine fruits, among others. Aspergillus carbonarius, the most probable source of OTA in these commodities, achieved its highest level of isolation at harvesting. So, it is obvious that the risk of OTA production increases sharply with the ripening of berries.

We became involved in this research a few years ago, collaborating with the Catalan Institute of the Vineyard and Wine (INCAVI), thanks to different projects focused on the OTA contamination of wine, supported by the Spanish and the Catalan Governments. We have continued these studies in the framework of the European project WINE-OCHRA RISK.

Our research group has a long-standing interest in veterinary and food mycology. In the field of mycotoxicology, we described the OTA production by A. niger (Abarca et al., Appl. Environ. Microbiol. 60: 2650-2652, 1994), an important species in biotechnological processes. Recently, we reported the importance some black aspergilli as sources of OTA contamination in wine (Cabañes et al, Int. J. Food Microbiol. 79: 213-215, 2002) and dried vine fruits (Abarca et al., J. Food Protect. 66: 504-506, 2003).

The European Union has regulated the maximum limits for OTA in an increasing number of food commodities, including dried vine fruits and wine. Our results contributed to knowing the fungi responsible for the OTA contamination of wine grapes. This is the first step needed in order to reduce the OTA risk in wine and also for minimizing the exposure of consumers to this mycotoxin.