Varietal Terpenoids and C13-Norisoprenoids in Alentejo Varietal Red Wines Across Two Vintages by HS-SPME–GC–TOFMS

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.