## 2 Materials and Methods  
### Berries and Commercial Products  
The analysis was carried out on 38 laboratory-produced juices (more precisely, on 22 samples of black currant juice (16 samples of enzyme juice and 6 samples of non-enzyme juice) and 16 samples of red currant juice (10 samples of enzyme juice and 6 samples of non-enzyme juice)). The juices were laboratory-prepared from hand-picked berries of black currant (cultivars Ojebyn, Titania, Othello, Ben Hope, Red Hube, Viola, and unknown) and red currant (cultivars Rovada, Heinemann's R.S., Jonkheer van Tets, and unknown) collected from various geographic locations in the Czech Republic between 2020 and 2021(see Table 1). Immediately after harvesting, the fruits were frozen and stored at \(-18\)\({}^{\circ}\)C until processing. Unfortunately, due to crop frost or low yields of current berries, it was not possible to compare all varieties from the first year of the study. Therefore, the samples were replaced by other varieties, but the number of samples with and without enzyme addition in the two-year experiment was maintained (Table 1). Furthermore, we controlled the chemical composition of 19 samples of commercial products (more precisely, 8 homogenates, 4 concentrates, and 7 nectars; see Table 2), which were purchased on the Czech market or directly from the Czech producers: Pepsico CZ, Ltd. (Prague, Czech Republic), Mattoni 1873 a.s. (Kyselka, Czech Republic), and Hame Ltd. (Kunovice, Czech Republic). All samples were stored in a freezer (\(-18\)\({}^{\circ}\)C) before processing or/and analysis. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & \multicolumn{6}{c}{**Black Currant (BC, _Ribes niform_ L)} \\ \hline
**Sample No.** & **Cultivar** & **Harvest** & **Enzyme** & **Juice Yield** & **Sample** & **Cultivar** & **Harvest** & **Enzyme** & **Juelic Yield** \\
**No.** & **Cultivar** & **Period** & **Addition** & **[\%]** & **No.** & **Cultivar** & **Period** & **Addition** & **[\%]** \\ \hline
1/20 & Öbryn & & & 69.2 & 1/21 & Red Hube \({}^{\prime}\) & & & 73.2 \\
2/20 & Titania & & & 71.2 & 2/21 & Titania \({}^{\ast}\) & & & 67.7 \\
3/20 & Titania \({}^{\ast}\) & & & 68.1 & 3/21 & Öbryn \({}^{\circ}\) & & & 67.2 \\
4/20 & Öbello & & & 72.4 & 4/21 & - & & & 74.4 \\
5/20 & Öbryn \({}^{\circ}\) & & & 67.7 & 5/21 & Viola & & & 65.3 \\
6/20 & Ben Hope & & & 72.7 & 6/21 & Titania & & & 69.3 \\
7/20 & Red Hube \({}^{\prime}\) & 2020 & & & 69.8 & 7/21 & - & & 70.7 \\
8/20 & - & & & 56.4 & 8/21 & - & & 73.6 \\ \hline
9/20 & - & & & 78.9 & 9/21 & - & & & 72.7 \\
10/20 & Öbello & & & 64.6 & 10/21 & - & & & 67.7 \\
\begin{tabular}{c} Juice yield \\ condition \\ \end{tabular} \\ \hline
12/20 & Rovada & & 71.3 & 12/21 &
\begin{tabular}{c} Heinemann’s \\ R.S. \\ Jonkheer \\ van Tets \\ \end{tabular} & with & 77.9 \\
13/20 & - & & with & 75.9 & 13/21 &
\begin{tabular}{c} Jonkheer \\ van Tets \\ \end{tabular} & with & 80.9 \\
14/20 & - & & 79.4 & 14/21 & - & & 80.0 \\
15/20 & - & & 83.0 & 15/21 & - & & 76.2 \\
16/20 & - & & 80.8 & 16/21 & - & & 80.0 \\ \hline
17/20 & - & & 81.7 & 17/21 & - & & & 78.5 \\
18/20 & - & without & 78.1 & 18/21 & - & & without & 73.6 \\
19/20 & - & & 70.6 & 19/21 & - & & 75.8 \\ \hline \end{tabular} Note. \({}^{\ast}\), \({}^{\circ}\), \({}^{\prime}\) = varieties from the same farmer.  
\end{table} 
Table 2: Samples of selected commercial products. For the laboratory preparation of currant juices, the addition of a solution of the enzyme preparation (pectinase) Rohapect MC (AB Enzymes GmbH, Darmstadt, Germany) and the juicer Sana Supreme 727 (Mipam bio Ltd., Ceske Budejovice, Czech Republic), with homogenising attachment and juicing sieve attachment, were used. A solution of the enzyme preparation Rohapect MC was prepared by weighing 2 g into a 50 mL volumetric flask and making up to the mark with distilled water. The berry samples stored in the freezer were thawed to room temperature before processing (cleaning, defrosting).