Water Stress Effects on Free and Bound Volatile Compounds in Macabeo and Chardonnay Grapes Analyzed Through GC×GC/ToFMS

Climate change and variable rainfall are pushing the wine industry to assess grapevine adaptability, as water deficit alters volatile compounds and understanding these processes is key to maintaining wine quality. A total of 64 compounds, free and glycosidically bound fractions, were analyzed using HS-SPME-GC×GC/ToFMS in Macabeo and Chardonnay grapes under two water irrigation regimes. Results showed that water availability significantly influenced aroma composition. Macabeo showed a strong response to rainfed conditions, with higher levels of monoterpenes, norisoprenoids and sesquiterpenes, mainly in the bound fraction, suggesting a metabolic adaptation to preserve aromatic potential. Chardonnay showed a more stable bound fraction and moderate changes in specific volatiles. These findings indicate that this advanced chromatographic technique allows a detailed evaluation of aroma precursors and their modulation by water availability.