http://hdl.handle.net/10174/23 2026-07-30T01:16:17Z http://hdl.handle.net/10174/42293 Title: GCxGC-TOFMS with flow modulation for fingerprinting volatile compounds in Portuguese grape varieties Authors: Fonseca, Daniela; Martins, Nuno; Garcia, Raquel; Cabrita, Maria João Abstract: Comprehensive two-dimensional gas chromatography offers a powerful analytical tool for profiling volatile compounds in complex matrices. The characterization of grapevine varieties that are resilient to water stress, such as autochthonous varieties, while safeguarding quality characteristics, is fundamental to viticulture. For this reason, the objective of this study was to characterize the volatile composition of four white varieties from the Alentejo region (Portugal), subjected to three different irrigation regimes: water comfort, moderate water deficit, and rainfed. The first step was to optimize the modulation conditions, and it was found that the most effective modulation period was 5 s, with a flush time of 0.20 s. After optimizing these conditions, the grapes of the Diagalves, Manteúdo, Perrum and Rabo de Ovelha varieties were analyzed by HS-SPME-GCxGC-TOFMS. A total of seventy-six volatile compounds, of which fifty-one were varietal volatiles, were identified and semi-quantified in these varieties. The results reveal that the irrigation regime influences the volatile profile with varying responses across the varieties. While Diagalves exhibited no significant differences between irrigation regimes, Manteúdo and Perrum demonstrated higher levels of varietal volatile compounds, particularly terpenes and C13 norisoprenoids, under rainfed conditions. According to PCA, irrigation regimes affect each variety differently. In conclusion, Manteúdo and Perrum emerge as the most statistically promising varieties in terms of adaptability to water scarcity. These findings highlight the significance of selecting resilient autochthonous grape varieties as an effective strategy to mitigate the impacts of climate change while maintaining the wine's distinctive aromatic character. 2026-01-01T00:00:00Z http://hdl.handle.net/10174/41869 Title: Water Stress Effects on Free and Bound Volatile Compounds in Macabeo and Chardonnay Grapes Analyzed Through GC×GC/ToFMS Authors: Cebrián-Tarancón, Cristina; Martins, Nuno; Fonseca, Daniela; Cabrita, Maria João; Salinas, Rosário; Alonso, Gonzalo; Sánchez-Gómez, Rosario Abstract: 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. 2026-01-01T00:00:00Z http://hdl.handle.net/10174/41796 Title: Profiling the Aroma of Grape Spirits for Port Wine Using a Multi-Analytical GC Approach and Sensory Analysis Authors: Caldeira, Ilda; Loureiro, Maria; Martins, Nuno; Lourenço, Silvia; Cabrita, Maria joao; Silva, Ricardo; Rocha, Silvia; Alves, Fernando Abstract: Port wine production involves the addition of grape spirit to halt fermentation and retain natural sweetness. This spirit, produced by distilling wine and its by-products, must comply with legal standards, including a mandatory sensory assessment. Because grape spirit influences Port wine’s volatile composition, this study investigated the odouractive compounds present in several grape spirits intended for fortification. Volatile compounds were extracted by liquid–liquid extraction, concentrated, and analysed using gas chromatography–olfactometry (GC-O) and gas chromatography–mass spectrometry (GC-MS). In GC-O, based on frequency detection, a panel of assessors sniffed the extracts to determine the presence of aroma compounds. The results revealed a wide range of odour-active compounds in grape spirits, belonging to several chemical families such as esters, alcohols, terpenic compounds and acids. These compounds exhibited both pleasant aromas, such as fruity, floral and caramel notes as well as undesirable ones like cheese and foot odour. Most of these compounds originate from the fermentation process and are also found in other unaged distilled beverages, including young Cognac, Calvados and fruit spirits. This research highlights the aromatic complexity of grape spirits and, for the first time, determined the aroma thresholds for 25 of 36 the compounds studied at an ethanol content of 20%. 2026-01-01T00:00:00Z http://hdl.handle.net/10174/41795 Title: Varietal Terpenoids and C13-Norisoprenoids in Alentejo Varietal Red Wines Across Two Vintages by HS-SPME–GC–TOFMS Authors: Gastão-Muchecha, Sousa; Martins, Nuno; Garcia, Raquel; Cabrita, Maria João Abstract: This study characterizes the volatile organic compound (VOC) profiles of young monovarietal red wines from five cultivars widely grown in Alentejo, Portugal—Aragonez, Castelão, Merlot, Syrah, and Trincadeira, across two consecutive vintages (2021 and 2022), in a total of 20 samples. Understanding how grape variety and harvest year shape VOC composition is essential for defining varietal typicity, supporting authenticity assessments, and guiding quality-driven enological practices. VOCs were extracted using headspace solid-phase microextraction (HS-SPME) and analyzed by gas chromatography coupled to time-of-flight mass spectrometry (GC–TOFMS), providing a semi-quantification of 142 volatile compounds across nine chemical families. Statistical analyses, including ANOVA and Principal Component Analysis (PCA), unveiled significant effects of variety, vintage, and their interactions on VOC composition, enabling clear discrimination of the wines. Notably, terpenes and C13-norisoprenoids exhibited strong varietal differentiation patterns: Castelão and Trincadeira showed higher relative proportions of monoterpenes like linalool, β-citronellol, and geraniol, whereas Aragonez presented increased sesquiterpene levels including β-bisabolene and α-muurolene, and Syrah and Merlot displayed more diverse terpenoid patterns. Despite their lower abundance, C13-norisoprenoids, particularly trans-β-ionone, consistently differentiated wines across vintages. A 100% ribbon chart of the main terpenoids and C13-norisoprenoids highlighted genotype-driven and vintage-independent patterns, underscoring their potential as robust markers of Portuguese red wines. This study presents a high-resolution HS-SPME–GC–TOFMS chemometric workflow for the profiling and classification of young Alentejo red wines, highlighting consistent varietal patterns in terpene and C13-norisoprenoid distributions under the studied conditions. 2026-01-01T00:00:00Z