## 3 Results and Discussion
### Effect of Cultivar on Volatile Composition of Currants
Esters ranged from 26.3% to 57.0% in red/white cultivars and from 23.5% to 43.4% in black cultivars, with ethyl propanoate significantly predominating in all cultivars. Incontrast to [PERSON] [26], a quantitative preponderance of ethyl esters compared to methyl esters was observed. Nearly all identified esters were present in all cultivars: methyl acetate (0-104.2 \(\upmu\)g/kg), ethyl acetate (4.9-38.3 \(\upmu\)g/kg), butyl acetate (4.9-112.6 \(\upmu\)g/kg), ethyl propanoate (80.9-859.0 \(\upmu\)g/kg), methyl butanoate (4.7-57.9 \(\upmu\)g/kg), ethyl butanoate (8.7-149.2 \(\upmu\)g/kg), and octyl acetate (0-13.2 \(\upmu\)g/kg). Consistent with [PERSON] [26], they varied considerably depending on the cultivar, except for ethyl decanoate (\(p\) = 0.09), which was present in a range of 4.0-34.6 \(\upmu\)g/kg, while published studies have found it only in traces in black currants (see Table S2). Consistent with our results, [PERSON] et al. [17] and [PERSON] [26] state that black currant berry profiles are dominated by short-chain esters, mentioning methyl and ethyl butanoate as the main ones, which also significantly prevailed in our black cultivars over the red ones. [PERSON] et al. [14] also found high amounts of hexyl esters, which were not present in our samples. Terpenes and terpenoids, the largest group of plant secondary metabolites, are not present in abundant levels in fruits [17]. They were more typical and abundant in black cultivars (6.0-20.4%) compared to red/white cultivars (1.8-10.6%). Consistent with our results, [PERSON] [26] and [PERSON] and [PERSON] [9] observed large variations in the proportions of most terpen and terpenoids. \(\upmu\)g-Pinene (0-46.6 \(\upmu\)g/kg), linalool (3.5-74.5 \(\upmu\)g/kg), and \(\upmu\)g-damascenone (3.0-11.5 \(\upmu\)g/kg) were present in all cultivars. [PERSON] et al. [7], consistent with our results, stated that monoterpenoids are the most abundant among terpenoids, with limone, \(\upmu\)g-3-carene, and \(\upgamma\)-terpinene prevailing. [PERSON] et al. [17] also mentioned \(\upmu\)g-damascenone, but it was only present in small quantities in our samples. Ketones, consistent with the study by [PERSON] et al. [17], showed low levels (<4%) in all cultivars, as did acids. Comparing our results with the literature is difficult because relatively few studies analyze fresh berries. More often, different products are analyzed [8; 13], and the aromatic profile is then influenced by technological operations such as homogenization, juice extraction, or heat treatment. Moreover, only some studies report exact quantities (\(\upmu\)g/kg) [6; 17; 26]; others express results as relative percentages [9; 12]. For clarity, Table S2 shows the concentration range of each compound reported in the literature. As can be seen, the variability of individual compounds between studies is quite large, as in our case, but all coincide on the presence of significant differences between cultivars, mainly in compound content. Regarding red/white cultivars, the quantitative representation of chemical groups was as follows: esters > alcohols > aldehydes > terpenes > ketones > acids. As mentioned previously, these have been scarcely investigated, and a direct comparison of red/white versus black currants has not yet been published. [PERSON] [26] is one of the few who analyzed red currants and compared them to black currants. In contrast to our results, they found a high concentration of acetic acid as a distinctive feature of red currants; however, they did not find any esters, while [PERSON] et al. [18] found esters to make up more than 40% of the aroma profile of \(R\). _rubrum_. Similarly, in our study, esters were quantitatively the most important group, constituting 30.8-57.0% in white cultivars and 26.3-49.7% in red cultivars. As in the case of black currants, C\({}_{6}\) compounds formed a significant group, with (E)-2-hexenal predominating, and relatively low concentrations of terpen were found (<10%).