The Australian Wine Research Institute’s Analytical Service - Analyses

Ochratoxin A in grapes and wines

Ochratoxin A (OA) is a toxin produced by certain fungi belonging to the genera Aspergillis and Penicillium. The predominant species producing OA are Aspergillus ochraceus (also referred to as A. alutaceus) and A. carbonarius, and Pencillium verrucosum.

Fungi producing OA only become established on the substrate after crops have been infected by pathogenic organisms or if physical or physiological damage has occurred. Generally, growth of these fungi is restricted to dead plant tissue and they form the predominant fungi causing spoilage of fruits, including grapes. Thus, OA has been detected in grape juice and wine. Cool conditions favour production of this fungal metabolite. This is in contrast to most commonly encountered instances where hot conditions promote fungal contamination problems.

There is limited information on the conditions that favour the development of infection in grapes. The incidence of infection, and hence contamination of grapes and wine with OA is perceived to be infrequent and irregular, where pre-vintage conditions, viticultural and vinification practices may influence the incidence of OA contamination.

After considerable time, the EC has modified existing regulations, setting a limit of 2 µg/L in wine. This is to take effect from the 2005 harvest (www.oiv.int/uk/accueil/index.php).

The method used by the Trace Analytical Laboratory is fully validated and very robust. We have participated in numerous proficiency tests for analysing OA in wine and hold NATA accreditation for this method.