Modulating the Chemical and Sensory Profile of Avgoustiatis Grapes (Vitis Vinifera L.) and Wines: The Impact of Irrigation and Post-Harvest Dehydration Under Extreme Mediterranean Thermal Stress

This study evaluates regulated deficit irrigation (IR) and post-harvest dehydration (DH) as complementary strategies to mitigate extreme thermal stress on the red grape variety Avgoustiatis during the hot 2024 vintage. Analysis of the berries reveals that while IR significantly expanded vine productivity to 2.75 kg/vine compared to 1.32 kg/vine recorded in control vines (CO), it successfully maintained berry weight (240 g). Conversely, DH induced controlled water loss, reducing berry weight to 93 g and concentrating must sugars to 27.3 °Brix, relative to the 23.2 °Brix observed in IR. Crucially, both IR and DH prevented the thermal degradation of total acidity (6.73 g/L and 7.25 g/L respectively) which caused by heat stress in CO samples (6.21 g/L). In the finished wines, both practices increased colour intensity by lowering anthocyanin extractability. However, chemical profiling clearly differentiated the treatments with DH maximized skin tannins (164.7 mg/L), yielding highly structured, astringent wines characterized by plum aromas driven by elevated nerol content (492.91 μg/L). Conversely, IR wines presented a more complex volatile profile, boosting fruity and floral notes. In conclusion, as irrigation becomes increasingly restricted by water scarcity under climate change, post-harvest dehydration offers an effective alternative for producing premium, structurally dense red wines.