Assessment of Grape Over-Ripening Dynamics as a Post-Harvest Technique in the Vineyard

Abstract

The consequences of climate change are prompting the development of strategies to adapt viticultural practices to increasingly warmer and drier climatic scenarios. In this context, grape sun-drying emerges as a potential resilience strategy for the production of overripe grapes for winemaking. This study focuses on comparing grape sun-drying practices carried out between vineyard rows as an alternative to the traditional technique (asoleo), evaluating the differences derived from location and drying surface. Over two vintages, grape clusters of Pedro Ximénez variety from both conventional and organic management managements were partially dried using two different surfaces: food-grade plastic and food-grade plastic mesh. The sun-drying process was monitored through weight loss, drying kinetics, and changes in grape musts physicochemical composition. Inter-row sun-drying reduced grape handling and eliminated the need for dedicated drying areas, while helping to preserve grape sanitary integrity. Food-grade plastic, due to its higher temperature retention, promoted greater water loss and higher sugar concentration. In contrast, the shading effect provided by the vine canopy in inter-row settings allowed for more balanced dehydration dynamics. Moreover, gluconic acid levels indicated that organic grapes preserved better sanitary integrity than conventional ones, suggesting that pre-harvest phytosanitary treatments may increase susceptibility to microbial development during sun-drying. The results support inter-row grape sun-drying as a practical and sustainable alternative to the traditional asoleo technique, particularly under warm climate conditions.