## 3 Results and Discussion
### Volatile Compounds
#### 3.4.3 Aldehydes and Ketones  
Acetaldehyde is the most prevalent aldehyde in wine, accounting for over 90% of the total aldehyde content. It is produced as an intermediate during fermentation by the conversion of sugars to ethanol via pyruvate decarboxylation by yeast pyruvate decarboxylases. Its portion is further converted into ethanol by alcohol dehydrogenases and into acetic acid by aldehyde dehydrogenases. These processes are regulated by specific yeast genes and influenced by fermentation conditions. Further, acetaldehyde is partly enzymatically transformed into acetoin, a ketone precursor to 2,3-butanediol and diacetyl. Acetaldehyde affects wine aroma differently depending on its concentration. At low levels, it boosts fruity notes, moderate concentrations evoke nutty aromas, and at high levels, it develops an odour similar to overripe apples [48]. Other aldehydes can be formed from amino acids and pyruvate via \(\alpha\)-keto acids intermediates [49]. Unsaturated alkenals are a \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Co.**} & \multirow{3}{*}{**Volatile Compounds**} & \multirow{3}{*}{**ID**} & \multirow{3}{*}{**LRI\({}_{\text{e}}\)**} & \multirow{3}{*}{**LRI\({}_{\text{1}}\)**} & \multicolumn{6}{c}{**Differences in Concentration**} \\ \cline{5-10}  & & & & \multicolumn{4}{c}{**One-Way ANOVA**} & \multicolumn{4}{c}{**Two-Way ANOVA**} \\ \cline{5-10}  & & & & **2021** & & **2022** & & & \\ \cline{5-10}  & & & & & **SCE** & **SPA** & **SCE** & **SPA** & **H** & \(\mathbf{Y}\times\mathbf{H}\) \\ \hline TE61 & Cadalene & B, C & 2227 & 2226 & 0.19 & 0.12 & 0.12 & 0.12 & n.s. & **21** & * \\ TE62 & 2-3-Dihydrofarmesol & B, C & 2260 & 2265 & n.d. & n.d. & 0.13 & 0.11 & - & - & - \\ TE63 & _cis,trans_-Famesol & B, C & 2350 & 2351 & 0.11 & 0.49 & 0.10 & 0.12 & **SPA** & **21** & n.s. \\ \hline \hline \end{tabular} Abbreviations: Co.—compound’s code; ID—identification of compounds: A—retention time accordant with that of a pure standard; B—mass spectra accordant with that from NIST 2.0, Wiley 8, and FFNSC 2 mass spectra electronic libraries or literature; C—linear retention index (LRI) accordant with an index from literature (compounds with only B in the ID column were considered tentatively identified); LRI—experimental linear retention index (LRI\({}_{\text{1}}\)—linear retention index from literature; n.s.—not significant; n.d.—not detected. One-way ANOVA section: different superscript lowercase letters represent statistically significant differences between the two investigated wines determined by one-way ANOVA at \(p<0.05\) for each harvest year separately. Two-way ANOVA section: designations are reported representing yeast (SCE, SPA) and harvest year (21, 22) with higher concentration determined by two-way ANOVA at \(p<0.05\) with yeast (Y) and harvest year (H) as factors. An asterisk indicates a significant interaction between the two factors (Y \(\times\) H). Significant differences are highlighted in bold.  
\end{table} 
Table 4: _Cont._product of the degradation of unsaturated long-chain fatty acids [48]. The formation and further conversions of both aldehydes and ketones are strongly affected by the activity of yeast. In this study, SPA wines consistently showed significantly higher acetaldehyde concentrations across both harvest years (Table 6). Heptanal levels were elevated in SCE-21 wine, while 2-(acetoxy)-propanal concentrations were higher in SCE-22 wines compared to their SPA counterparts. SPA wines were characterized by increased levels of specific ketones compared to control SCE wines, including acetoin in 2021, 2-ethyl-3-methoxy-2-cyclopentene and 1,2-dihydroxycyclobutene-3,4-dione in 2022, and 3-(acetoxy)-4-methyl-2-pentanone in both years (Table 7). In contrast, _S. cerevisiae_ produced higher amounts of 2-heptanone, 2-nonanone, 2-decanone, and 2-dodecanone in both years, as well as 1-hydroxy-3-methyl-2-butanone, 2,4-nonanedione, 2-undecanone, and \(p\)-tert-butylcyclohexanone in certain years.