Influence of oak chips, glutathione-rich inactivated yeast, and oxygen during fermentation on the analytical profile of volatile compounds in Blaufränkisch wines

Blaufränkisch is an emerging grape variety with promising resilience to climate change due to its distinctive viticultural and oenological characteristics. This study employed a homogeneous Blaufränkisch mash to investigate the effects of oak chips, glutathione-rich inactivated yeast (GSH-IDY), and oxygen addition during fermentation on the concentration of volatile aroma compounds. The objective was to assess changes in the analytical aroma profile of the resulting wines and to evaluate the response of both varietal and fermentation-derived compounds to these treatments. Approximately 80 volatile compounds were quantified using compound-class-specific gas chromatography-mass spectrometry (GC-MS) techniques, including SIDA-HS-SPME-GC-MS for esters and alcohols, HS-SPME-GC-SIM-MS for monoterpenes and C13-norisoprenoids, and derivatisation-based SPE-GC-TQMS for polyfunctional thiols. Oak chips significantly altered the concentration of specific aroma compounds: polyfunctional thiols such as 3-sulfanylhexan-1-ol (–24 %) and 4-methyl-4-sulfanylpentan-2-one (–26 %)—associated with grapefruit and blackcurrant notes—were reduced, whereas GSH-IDY and oxygen showed only marginal effects. Oak chips also enhanced the formation of 2-furfurylmethanethiol (+26 %), a compound that contributes to roasted aroma characteristics. Monoterpenes (e.g., linalool and citronellol) and C13-norisoprenoids remained largely stable, with GSH-IDY exerting a slight preservative effect. There were notable changes among C6 alcohols: oak chips decreased trans-2-hexen-1-ol (–40 %) and hexanol (–15 %), while GSH-IDY promoted hexanol stability. Higher alcohols and esters responded differently: oak chips increased isoamyl alcohol concentrations (+10 %), whereas GSH-IDY promoted the formation of butanol (+16 %), while oxygen increased levels of key esters such as diethyl succinate (+36 %) and ethyl octanoate (+15 %). Overall, this study highlights how targeted fermentation treatments influence the volatile profile of Blaufränkisch wines.