Fruit spoilage and ochratoxin a production by Aspergillus carbonarius in the berries of different grape cultivars

Fruit spoilage and the production of ochratoxin A (OTA) by Aspergillus carbonarius are major causes of contamination of grape products. An OTA-producing strain of A. carbonarius 090614 was used to inoculate three grape cultivars, Thompson seedless, Kyoho, and Red Earth, via manual damage and non-damaging inoculations. Inoculated grape berries were incubated at 4, 25, and 30 °C, respectively. During the incubation, the diameter of rotten part of the berry, OTA accumulation, and reducing sugar content, soluble solids, total acidity, and pH were measured every day until the grape berries were completely rotted. No fungal colonization and OTA production were observed for all surface inoculated grape berries at all temperatures and in invasively inoculated grape berries incubated at 4 °C. Progression of the rotted area of the fruit and OTA accumulation were increased at 30 °C compared to 25 °C in all grape cultivars, and was the fastest for Thompson seedless, slow for Kyoho, and lowest for Red Earth berries. For all grape cultivars, reducing sugar content, soluble solids and pH decreased during cultivation, while total acidity content increased.