## 1 Introduction  
The selection of yeast for alcoholic fermentation is one of the most critical factors influencing the final composition and quality of wine. Currently, numerous yeast species and strains are isolated, selected, and commercially available, with various _Saccharomyces cerevisiae_ strains dominating due to their ability to conduct predictable and vigorous fermentations, tolerate relatively high levels of alcohol and sulfur dioxide, and function effectively across standard grape must pH ranges. In recent years, non-_Saccharomyces_ species, such as _Torulaspora delbrueckii_, _Lachancea thermotolerans_, _Pichia kluyveri_, _Metschnikowia pulcherrima_, and _Schizosaccharomyces pombe_, have gained attention as co-fermentation starters with _S. cerevisiae_ due to their potential to enhance specific wine quality attributes [1; 2]. Another yeast from the _Saccharomyces sensu stricto_ complex, _Saccharomyces paradoxins_, has also demonstrated promising fermentation performance [3; 4; 5]. Unlike _S. cerevisiae_ and other _S. sensu stricto_ species, which are primarily associated with human fermentation environments, _S. paradoxus_ is predominantly found in natural ecosystems, although it is rarely isolated from vineyards [5; 6; 7; 8]. Several studies have reported that _S. paradoxus_ strains can reduce volatile acidity and malic acid levels while increasing the glycerol concentration in comparison to _S. cerevisiae_-driven fermentations [3; 4; 5; 5; 9]. Furthermore, some _S. paradoxus_ strains were found to exhibit higher concentrations of yeast cell wall chitin. This characteristic enables them to bind grape chitinases more efficiently than conventional _S. cerevisiae_ strains, in this way enhancing wine protein haze stability [10; 11]. The effect of _S. paradoxus_ on volatile compounds--key contributors to the aroma and flavour profile of wine--is still unclear. A few existing studies showed contrasting results, with alterations in the concentrations of higher alcohols, fatty acids, and volatile esters, depending on the specific strain and compound. The obtained volatile profiles were generally comparable to those obtained by _S. cerevisiae_ controls, highlighting the promising potential of _S. paradoxus_[4; 5; 12; 13]. Despite these insights, the potential of _S. paradoxus_ in commercial winemaking remains largely untapped, accompanied with significant gaps in the literature regarding this topic. Existing studies have primarily focused on standard physico-chemical parameters and, in some cases, a limited number of volatile compounds [4; 5; 12; 13]. In this way, numerous potentially important effects remained unexplored. The effects of _S. paradoxus_ fermentation on other key wine constituents, such as phenolic compounds and protein classes beyond chitinases, have not been studied to date. Additionally, most research on _S. paradoxus_ and wine yeasts in general has been limited to single-season studies, overlooking potential year-to-year variability in fermentation outcomes due to variable grape composition. The main hypothesis of this study is that _S. paradoxus_ fermentation produces a distinct white wine chemical composition compared to standard _S. cerevisiae_, with a broader impact than currently recognized. Building on this foundation, the primary objective was to expand the investigation into the effects of _S. paradoxus_ on a significantly larger array of wine components by employing integrated standard and metabolomics approaches. The main focus was set on volatile aroma and flavour compounds, which are crucial for wine quality and distinctiveness. To achieve a comprehensive volatilome characterization, an advanced state-of-the-art analytical technique, comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC \(\times\) GC/TOF-MS), was employed. This technique involves the use of two gas chromatographic columns with differing polarities and lengths, connected in series.