GCxGC-TOFMS with flow modulation for fingerprinting volatile compounds in Portuguese grape varieties

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.