## 3 Results and Discussion
### Volatile Compounds Identified in Currant Samples Using HS-SPME-GC-FID/MS Method  
Fruit flavor is closely related to the content and composition of volatile (aroma) compounds, which can be measured instrumentally. Therefore, the sensory evaluation was supplemented by volatile compound analysis. This approach has been particularly understued in red and white currants. A total of 54 volatile compounds were identified in the 15 analyzed currant cultivars using HS-SPME-GC-FID/MS. They were classified into six groups based on their chemical characteristics: alcohols (14), aldehydes (11), esters (12), terpenes and terpenoids (14), ketones (2), and an acid (1). An overview, indicating their presence in each variant (red/white/black), is provided in Supplementary Material Table S1. All these compounds, except ethyl heptanoate, have been previously found in black currants by numerous authors [6; 7; 10; 12; 13; 14; 17] and are known to be aroma-active. However, as shown in Table S1, their aroma descriptions from the open-access PubChem database can vary significantly depending on factors such as their concentration in sample, the sensitivity of the evaluator, etc. The volatile profile of black currants has been investigated for several decades, with over 200 aroma compounds identified. Most authors report alcohols, esters, terpenes, and terpenoids as major components [9; 12; 13; 16; 17]. This study also found aldehydes to be a substantial group. Alcohols were the most abundant compounds identified in all samples. Several metabolic pathways are involved in their biosynthesis. Six primary alcohols--ethanol, butan-1-ol, pentan-1-ol, hexan-1-ol, octan-1-ol, and nonan-1-ol--were identified. These are formed by enzymatic reduction of corresponding aldehydes by alcohol dehydrogenases. Free ethanol is a product of fermentation and is found in very small quantities in fruit; however, bound in esters, it is a common component of fruit aroma [31]. Other short-chain (\(<\)C\({}_{18}\)) primary alcohols contribute to the characteristic flavors of fruits, but according to [PERSON] et al. [17], they do not significantly contribute to currant aroma in their free form. They are less important than their aldehyde homologs due to higher odor thresholds [31]. Among these, only hexan-1-ol, generated from linoleic acid as part of the C\({}_{6}\) group, was recognized as an important contributor to black current aroma [6]. The identified secondary alcohols, butan-2-ol and pentan-2-ol, are assumed to be formed by enzymatic reduction of corresponding methyl ketones. The branched-chain alcohols, 2-methylpropan-1-ol and 3-methylbutan-1-ol, are derived from amino acids (Leu, Ile) [31]. Among these, 3-methylbutan-1-ol, along with the unsaturated C\({}_{6}\) alcohols (E)-2-hexen-1-ol and the isomers (E)- and (Z)-3-hexen-1-ol, was previously recognized as a key component of black currant aroma [13; 16]. These are formed from the unsaturated linoleic and linolenic acids via the lipoxygenase pathway after plant tissue disruption [6]. 1-Octen-3-ol, known in cheese for its typical mushroom aroma, has also been isolated from plants and, surprisingly, identified as a key component of black currant aroma, contributing a floral note [12]. Five straight-chain aldehydes--ethanol, hexanal, octanal, nonanal, and decanal--were identified. They are formed via \(\beta\)-oxidation of unsaturated fatty acids; saccharides (glucose, fructose, and sucrose) or amino acids can also be precursors [31]. Octanal and nonanal were previously recognized as key aroma components of black currants [12; 13; 14; 16; 17]. Three unsaturated aldehydes--(E)-2-hexenal, (Z)-3-hexenal, and (E)-2-octenal--were identified. These, along with their corresponding unsaturated alcohols, are generated from the oxidative degradation of linolenic and linoleic acids by the lipoxygenase pathway [6]. (E)-2-hexenal was previously recognized as a key component of black currants [12].