DETECTION OF OCHRATOXIGENIC ASPERGILLI ON GRAPE BERRIES DURING DRYING FOR PRODUCTION OF “VIN SANTO”

Aspergillus carbonarius, A. niger and A. tubingensis are known to produce ochratoxin A (OTA), a secondary metabolite with very dangerous effects to animals and humans. The International Agency for Research on Cancer has classified OTA as a possible carcinogen to humans (group 2B). As a consequence, the European Commission has imposed regulatory limits for the maximum tolerable presence of this toxin in different foodstuffs. After cereals, grape products are accounted as a considerable source of human OTA intake. Based on the fungal requirements of environmental temperature and relative humidity, it is easy to suppose that wines, as the Tuscan “Vin Santo”, obtained from grapes partially dried for several months to concentrate sugar content to at least 30% (w/v), are potentially at risk more than table wines. In the present work, done in the “Azienda Agricola Montepaldi” (San Casciano Val di Pesa, Florence), we isolated from grape berries about 6x107 CFU, divided into six major fungal morphotypes. Among these 24 were typical colonies of Aspergillus spp. These colonies were processed in parallel using: (i) conventional culture methods that allowed their morphological description; (ii) a molecular approach based on sequencing of the internal transcribed spacer (ITS) region comprising the ITS1, the ITS2, and the intervening 5.8S rRNA gene. Due to the known high intraand interspecific variability of the ITS region, it was not difficult to identify the fungal morphotypes isolated from the berries. The Aspergilli belonged to the species A. tubingensis. Analysis to find isolates producing OTA is ongoing.