On-vine grape withering as a sustainable innovation to premium wine and maturity decoupling

Withering, a traditional post-harvest practice for premium wines such as Amarone and Recioto, involves grape dehydration to enhance concentration and complexity. This study compared two techniques applied to Corvina grapes: dehydration in fruttaio (FD) and on-vine withering after peduncle twist (PD), evaluating their effects on grape composition, wine quality, and transcriptome dynamics. FD accelerated sugar accumulation and berry weight loss compared to PD, though both methods ultimately reached similar sugar levels. In grapes, no significant differences emerged between FD and PD for total anthocyanins (1-1.5 mg kg^-1), polyphenols (2.5-3 mg kg^-1), or antioxidant capacity (≈1.5 mM g^-1). These results indicate that changes were largely driven by water loss, with anthocyanins and polyphenols remaining stable while antioxidant activity declined under both treatments. In wines, differences became more evident. FD-derived wines contained higher anthocyanin levels (1000-1900 mg L^-1) and polyphenols (20-29 mg L^-1), compared with PD wines, which retained greater antioxidant activity. The enrichment in FD wines reflects both solute concentration due to dehydration and ethanol-enhanced extraction during fermentation. Differences in antioxidant capacity could be linked to tannin structure and polymerization, affecting wine smoothness and astringency. Transcriptomic analysis identified approximately 10,000 differentially expressed genes, with significant shifts in stilbene and pectin metabolism, highlighting roles in stress adaptation and cell wall remodeling. FD berries exhibited stronger transcriptional responses, with more pronounced activation of stress-related genes, reflecting the faster dehydration dynamics of fruttaio conditions. In conclusion, while both withering methods produced grapes with comparable phenolic content, they resulted in distinct wine compositions and transcriptomic signatures. On-vine withering emerges as a promising sustainable approach, reducing energy demand while maintaining wine quality, an important advantage in the context of climate change and low-impact viticulture.