Müller-Thurgau, 2014: Samples were obtained from the Kubík winery (Velké Bílovice, Czech Republic). It is a high quality, fresh, young wine with a typical yellow-green color, spicy taste, and somewhat pleasant smell.

St. Lawrence Rosé, 2014: The samples were obtained from the same winery. It is a quality deep pink wine, with tones of strawberries in aroma and taste.

Blue Portugal, 2014: We obtained the samples of this wine from the Veverka winery (Čejkovice, Czech Republic). The wine is a soft ruby color, with the aroma of flowers. The tannin content provides it with an attractive expression.

Strawberry wine: This is made from the strawberry Fragaria annanassa, cultivar ´Karmen´. The fruits were stripped and crushed and were allowed to macerate for 12 hours before the mash was pressed. The juice was drained by sedimentation. Water and sucrose were added to achieve the desired acid reduction. Nitrogenous substances were also treated with nutrient salt. The juice was then inoculated with noble yeast and placed in an appropriate glass container, fitted with a fermentation plug, and allowed to ferment. After fermentation, the wine was removed from the sludge and filtered. Subsequently, the wine was bottled.

Elderberry wine: The wine was made from elderberries (Sambucus nigra, L.). The elderberry fruits were stripped and crushed. The mash was heated to 80 °C for 15 minutes, to destroy the sambunigrin, which causes headaches and nausea. Then the mash was macerated for 48 hours and subsequently pressed. The juice was drained by sedimentation. Water and sucrose were added to achieve the desired acid reduction. Nitrogenous substances were also treated with nutrient salt. The juice was then inoculated with noble yeast and placed in an appropriate glass container, fitted with a fermentation plug, and allowed to ferment. After fermentation, the wine was removed from the sludge and filtered, then subsequently bottled.

Apple wine: The wine was made from the cultivar ´Jonagold´. The apples were stripped of stalks and cores, then crushed. The mash was pressed, and the juice was drained by sedimentation. Water and sucrose were added to achieve the desired acid reduction. Nitrogenous substances were also treated with nutrient salt. The juice was then inoculated with noble yeast and placed in an appropriate glass container, fitted with a fermentation plug, and allowed to ferment. After fermentation, the wines were removed from the sludge and filtered, then, subsequently, was bottled.

For our research we used the followed methods:

For the determination procedure, see the description earlier (Sochor et al., 2010). We mixed 150 μL volume of the reagent (0.095 mM 2,2-diphenyl-1-picrylhydrazyl; DPPH•) with 15 μL of wine sample. Each process was repeated twice. All samples were incubated for 10 minutes. After incubation, we measured samples at an absorbance of 505 nm on the spectrometer. The results were expressed as trolox equivalents.

These measurements were performed using recognized spectrophotometric methods (Zoecklein et al., 1999). The wine sample was placed into a 0.2 cm path-length quartz cuvette, then 200 μL of the sample and 1.8 mL of 1.1 M HCL were added and the resulting solution was thoroughly mixed and kept at room temperature for 180 minutes. A 0.22 M solution of K₂S₂O₅ was used as a blank.

The absorbance was read at 520 nm (A₅₂₀^HCl) for anthocyanins. Total concentrations of anthocyanin (mg.L^-1) were calculated as follows:

Total content of anthocyanins (mg.L^-1) = 4 × dilution × [A₅₂₀^HCl ‒ (5/3) × A₅₂₀^SO2]

Total flavanol content was estimated using the p-dimethylaminocinnamaldehyde (DMACA) method (Li, Tanner and Larkin, 1996; Tomášková et al., 2017). Compared with the widely used vanillin method, a major advantage of this method is that there is no interference from anthocyanins. Furthermore, it provides higher sensitivity and greater specificity. Wine (20 μL) was poured into a 1.5 mL Eppendorf tube and 980 μL of DMACA solution (0.1 % in 1 M HCl in MeOH) was added. The mixture was vortexed and allowed to react at room temperature for 12 minutes. Absorbance at 640 nm was then read against a blank sample prepared similarly but without DMACA. The total flavanol concentration was then estimated from a calibration curve and constructed by plotting known solutions of catechin (1 − 16 mg.L^-1) against A₆₄₀ (r² = 0.998). The results were expressed as mg.L^-1 of catechin equivalents.

The concentration of individual volatile substances in the wine was determined by the previously unpublished method of extraction with methyl t-butyl ether. The following was pipetted into a 25 mL volumetric flask: 20 mL of wine, 50 μL of 2-nonanol solution (500 mg.L^-1), and cyclopentanone (25 g.L^-1) in ethanol as the internal standard, and 5 mL of saturated (NH₄)₂SO₄ solution.

The flask contents were then thoroughly mixed, and 0.75 mL of extraction solvent added, MTBE with the addition of 1% neohexane. After thorough mixing of samples, and separation phases, the upper organic layer was transferred to a microtube with a portion of the resulting emulsion, centrifuged and the clear organic phase was dried over anhydrous magnesium sulphate. We continued using the treated extract for GC-MS analysis.

The aforementioned parameters were estimated using the ALPHA apparatus (Bruker, Germany). The ALPHA spectrometer is a compact FTIR analyser based on the principle of ATR sampling. Physical-chemical parameters of wine samples were determined according to the EEC Official Method by the European Commission (2003), which was used in a similar study by Condurso et al. (2018). This method of sampling considerably simplifies the preparation of samples for analysis. This means that samples of clarified wine were analysed directly, (i.e. without any adjustments), while those of musts and fermenting wine were centrifuged at 13 400 rpm for six minutes. Before the measuring of the first sample, the apparatus was thoroughly rinsed with distilled water and the background was measured using deionized water as a blank sample. For analysis, 1 mL of clear wine was sampled with a syringe; of this, one half (0.5 mL) was used for the rinsing of the system, and the remaining half (i.e. also 0.5 mL) was used for the subsequent three measurements. Depending on the method of calibration (musts/fermenting wine/fermented wine), the recorded resulting amounts were automatically evaluated by software.

Column: DB-WAX 30 m x 0.25 mm; 0.25 μM stationary phase (polyethylene glycol). Sample injection volume: 1 μL split ratio 1:5; carrier gas flow rate He:1 ml/min (linear gas velocity 36 cm.S^-1); injection chamber temperature: 180 °C. The initial column chamber temperature of 45 °C was maintained for 3.5 minutes, followed by a temperature gradient: up to 90 °C by 12 °C.min^-1 held for 0.75 minutes, up to 120 °C by 3 °C.min^-1.

For this study, we applied ANOVA, simple descriptive statistical methods, and correlation- regression. Statistical analysis was performed using NCSS 2019 software (ver. 19.0.4.; NCSS, LLC Utah, USA).

The results are shown in Table 1. The highest percentage of alcohol was determined in the elderberry wine samples, while the smallest percentage of alcohol was measured in the apple wine samples. The pH range was from 3.25 (apple wine) to 3.98 (elderberry wine). The lowest content of malic acid was determined in the samples of Blue Portugal and the highest content identified in the samples of Müller-Thurgau.

Lactic acid was maximal level in the samples of Blue Portugal, and minimal level in the apple samples. Zero acetic acid content was determined in the case of the apple wine and tartaric acid content in the elderberry wine samples.

On the contrary, the highest values were measured in the Blue Portugal (for acetic acid) and the Müller-Thurgau (for tartaric acid).

We also measured the value of zero in citric acid content, namely in the Müller-Thurgau, very low values in the St. Lawrence rosé and Blue Portugal, and high values in the strawberry wine. We found that the lowest values were of sucrose, of which we measured values close to zero, but we were able to determine higher fructose levels. The values of glucose were from 0.61 to 3.10 g.L^-1.

We observed that in the case of the grape wines, the analytical parameters were generally higher than in the case of the fruit wines. Among the grape wines, due to the analytical parameters, we evaluated Blue Portugal as the highest and, among fruit wines, we found that these values were the highest in the elderberry wine.

In the study by Robles et al. (2019), some organic acids were determined and identified in samples of wine. The study mentions that the following organic acids are found in Czech white grape wines: tartaric acid (4.4 – 17.4 mM), malic acid (12.4 – 46.4 mM), acetic acid (1.7 – 27.9 mM), and lactic acid (1.4 – 27.4 mM). The values of tartaric acid measured in our study were in the above range. The content of malic acid in the observed samples was below the levels of those in the above study. Only samples of Blue Portugal corresponded in a range of values of lactic acids. There were no similarities in the other grape wine samples to those in comparable research.

Higginson et al. (2015) demonstrate in their study that single berry samples taken from bunches (grape) showed a large variation in the content of tartaric acid and of malic acid across a single vine. This assayed variation is relevant for studies collecting samples of berries for organic acid analysis. We noted that grape berries (but not fruit) predetermined chemical and sensory properties.

The next aim of this study was to determine AOA, total anthocyanin content, and flavanol content in all the wine samples. After using statistical analysis methods, we came to the following conclusions:

The highest AOA was measured in the elderberry samples and the lowest content in the Müller-Thurgau samples.

Elderberry wine was the highest-scoring sample regarding total anthocyanin content. Otherwise, low levels were measured in the Müller- Thurgau and apple wine samples. The highest values of flavanol content were found in the Blue Portugal and elderberry wine samples, whereas the lowest values were determined in the Müller-Thurgau. All results are shown in Figure 1. Considering the above-measured parameters, we concluded that elderberry wine and Blue Portugal proved to be the wines with the highest content. Conversely, the lowest levels of measured parameters were demonstrated in the Müller-Thurgau and apple wine samples. By using the ANOVA statistical method, we showed a statistically significant difference between individual types of wine (grape and fruit wines; p ≤0.05). The correlation and regression method showed that all represented pairs of amounts appeared on a single line and that the function had a rotating character. We found that the coefficient was equivalent to +1, which ultimately means a greater degree of interdependence.

By comparing the various constituents of the wines, we assessed that, in terms of AOA, fruit wines contained higher values than grape wines. Furthermore, in terms of the total anthocyanin content, we evaluated fruit wines as higher than grape wines. However, the flavanol content increased with red wines, elderberry wine, and Blue Portugal, as confirmed by other studies (Vilas Boas et al., 2019; Lingua et al., 2015).

Bruno and Sparapano (2007) mentioned that the content of each substance in grapes was influenced by abiotic factors (e.g. by variety, parent soils, geographic situation, locality, and climatic conditions). We agreed with this statement and we added agricultural and horticultural methods and interventions in vineyards during the growing season. The studies by Wirth et al. (2010) and Baron et al. (2017) assert that the bioactive substance content and AOA in wine depends on wine-making technology, e. g. by the pressing, maceration, fermentation, filtration, and/or bottling techniques used. They also declare that these contributions have an effect on the sensory properties of wine, the storage time, and other indicators that promote human health.

The study Čakar et al. (2019) aimed to determine the potential of the strawberry and drupe (apricot, plum, and sweet cherry) fruits for the production of new fruit wines Improved with phenolic compounds. They found general results that showed that the same fruit wine samples presented high redox potentials, marginally lower than strawberry, and plum wine samples.

The antioxidative potential and total phenolic content were tested in elderberry must and wine in the study Schmitzer et al. (2010). The level of total phenolic content in elderberry must and wine was 2004.13 GAE.L^-1 and antioxidative potential of elderberry wine was equal to red wine. There was a detected correlation between total phenolic content and antioxidative potential of elderberry wine. Moreover, examinations of elderberry fruits in other studies showed that it contains high biological activity components, primarily polyphenols, mostly anthocyanins, flavonols, phenolic acids, and proanthocyanidins, as well as terpenes and lectins (Sidor and Gramza-Michałowska, 2015).

Mlček et al. (2019) concluded that adequate wine consumption leads to cancer prevention and another health disease. Studies dealing with the content of bioactive substances in beverages made from berries showed that in addition to beneficial effects on human health, these substances have also side effects, e. g. it may cause an allergic reaction for unexplained reasons (Sedláčková et al., 2018; Nunes et al., 2019; Snopek et al., 2019).

Table 2 shows the measured values of individual volatile substances. The fruit wines contained more methanol than the grape wines. The highest level of ethyl acetate was measured in the strawberry wine and other values were similar. Among the terpenes, the most significant that we identified were in the samples of strawberry wine (linalool 100 μg.L^-1; α-terpineol 43 μg.L^-1 and acetoin 9.7 mg.L^-1); compared to the strawberry wine, elderberry wine contained more acetoin, and apple wine was higher in methionol content. Lan et al. (2017) found that changes in taste properties in wine occur at an early stage of fermentation, i.e. 0 – 4 days. The content of aldehydes, ketones, heterocyclic and aromatic compounds were very reduced by fermentation. The same opinion was presented in studies Peng et al. (1997); Lubbers, Verret and Voilley (2001) and Spence, Velasco and Knoeferle (2014).

Comparing the values of volatile substances in grape wines, we found that Blue Portugal and Müller-Thurgau were wines with a relatively high content of linalool. Low total terpene content was demonstrated in samples of St. Lawrence rosé. Geraniol, methionol, and acetoin were measured; Müller-Thurgau differed substantially from Blue Portugal with the highest content of ho-trienol and α-terpineol. The only value of nerol was detected in the Blue Portugal sample. We definitively demonstrated fruit wines as wines with much greater values of volatile substances than grape wines. Moreover, we found statistically significant differences between the measured values (p ≤0.05).

Dziadas and Jeleń (2010) measured terpenes in white wines (different cultivars). As an example, we chose Riesling. The results showed that linalool reached a level of 16.6 – 54.4 μg.L^-1. Comparing it with Müller-Thurgau, we noted a higher level of linalool. In contrast, the content of α-terpineol was much lower in our examined samples than those of the results from the comparison study. The nerol content, of which almost none of the examined samples allowed an estimate, had been determined with a decisively higher content in the above research. Tarko et al. (2008) declared an opinion that red wines had higher antioxidant potential and total polyphenol content than analyzed white grape and fruit wines. The prevailing volatile compounds of wines were higher alcohols, mainly amyl alcohols and isobutanol. Different conditions of double fermentation were examined in a study Ubeda et al. (2011). There was added SO₂ and pectolytic enzymes which increased the level of methanol and acetaldehyde, especially in strawberry purees. In the study Kong et al. (2019) results showed that enzyme treatments improved the contents of volatile substances. The levels of terpenes and higher alcohols increased constantly during alcohol fermentation. Yang et al. (2020) and Bhat (2000) also mentioned the quality of fruit wines is related to the corrected application of enzymes in the process of winemaking.

Ayestarán et al. (2019) studied the effect of the winemaking process on the volatile composition and aromatic profile of Tempranillo Blanco wines.

The results showed that carbonic macerated wines had a higher level of alcohols and carbonyl compounds. We agreed with this statement.