UNCOVERING THE ROLE OF BERRY MATURITY STAGE AND GRAPE GENOTYPE ON WINE CHARACTERISTICS: INSIGHTS FROM CHEMICAL CHARACTERISTICS AND VOLATILE COMPOUNDS ANALYSIS

Abstract

In a climate change context and aiming for sustainable, high-quality Bordeaux wine production, this project examines the impact of grape maturity levels in various cultivars chosen for their adaptability, genetic diversity, and potential to enhance wine quality. The study explores the effects on wine composition and quality through sensory and molecular methods. We studied eight 14-year-old Vitis vinifera cv. grape varieties from the same area (VITADAPT plots 1 and 5): Cabernet Franc, Cabernet Sauvignon, Carmenère, Castets, Cot, Merlot, Petit Verdot, and Touriga Nacional. We examined three berry maturity stages from the 2022 vintage: mid-veraison (MV), mid-maturity (MM), 7 days before maturity (M-7), at maturity (M), and 10 days post-maturity (M+10). Classical composition parameters were monitored during maturation. Fine volatile compounds, including lactones, furanones, norisoprenoids, and carbonyls as ripening and over-ripening markers, were quantified in grapes and wines using SPME-GC-MS, while thiols were analyzed in wines by SPE-GC-MS/MS. For example, according to the maturity stages, a significant increase in alcohol content was observed, which varied depending on the grape genotype. The highest concentrations were found in Petit Verdot (13.78 g/L in M-7), Cabernet Sauvignon, Merlot, and Petit Verdot (15.21, 15.30, and 15.75 g/L in M) and Merlot (16.68 g/L in M+10). These values were directly related to the higher sugar concentrations found in their must during the evaluated periods. Total acidity and pH levels vary among cultivars and are also influenced by different maturation stages. Some cultivars show more significant changes over time, while others display more modest fluctuations. As expected, the pH values and total acidity in wines from different cultivars were inversely related. Concerning the analyzed volatile compounds, surprisingly, Petit Verdot exhibited the highest concentrations of γ-nonalactone, followed by Cabernet Sauvignon and Cot, at all maturity stages including M-7 (6.39, 3.90, 3.61 µg/L), M (20.98, 8.98, 6.05 µg/L), and M+10 (13.93, 12.40, 8.48 µg/L), respectively. Overall, this study offers a new method to assess varieties’ sensitivity to overripening and vital insights into the impact of berry maturity stage and cultivar on wine physicochemical traits and volatile compound profiles. These findings can be a foundation for future research aiming to predict or model wine’s chemical and sensory properties.