Modeling environmental conditions during grapes drying as these affect Ochratoxin A development

Specific indicators of environmental conditions and drying properties were analyzed using two grape cultivars (‘Crimson’ and ‘Thompson’), artificially inoculated with Aspergillus carbonarius under open-air and tunnel drying conditions. Air temperature (T), relative humidity (RH), grape surface temperature (Ts) and water activity (aw) throughout the drying experiment, grape moisture content, fungal colonisation and OTA contamination during the drying process and their interactions were analyzed. Drying properties such as effective water diffusivity (Deff) and water transfer resistant of the peel were estimated. Ts was 5-7°C higher in the tunnel than in the open-air; the infected grapes had a higher maximum Ts than the control (around 4-6°C). OTA contamination was higher in the tunnel than in the open-air-dried grapes, but fungal colonies showed the opposite trend. Water diffusivity (Deff) was 54% higher in the tunnel than in the open-air; infected grapes had more than 70% higher Deff than control grapes, differences explained by factors affecting the water transport. This study highlighted CFU and OTA as indicators affecting the water availability between red and white grapes during open-air and tunnel drying, as estimated by Deff and peel resistant.