## 3 Discussion
### The Polyphenol Content and Antioxidant Activity of Apple Wines  
Wines contain a variety of polyphenolic compounds, including phenolic acids, flavonoids, flavanols, tannins and anthocyanins. The content of polyphenolic compounds in wines is influenced by the species and variety of fruit, the degree of ripeness, fermentation and maturation conditions [44; 45]. The ageing of wines results in a change in the qualitative and quantitative composition of polyphenols, which is influenced by a number of factors, including the occurrence of copignmentation, condensation and polymerisation of these compounds [32; 46]. The presence of wood (barrels, staves, chips) during the ageing process also affects the profile of polyphenolic compounds in wines. The content of phenolic compounds is contingent upon the species of wood employed, the degree of toasting, the alcohol content of the wines and the contact surface of the beverage with the wood [47; 48]. The content of total polyphenols in apple wines aged with wood chips was dependent on the wood species (Table 2). Significantly higher values were found in wines aged with oak chips. [PERSON] et al. [49] demonstrated a sixfold higher concentration of phenolic compounds in samples extracted from oak wood in relation to cherry wood. However, these were model samples using a 55% hydroalcoholic mixture. The oak wood extracts exhibited a prevalence of syringaldehyde, coniferaldehyde and sinapaldehyde, with concentrations that were 5 to 8 times higher than those observed in the cherry wood extracts. Oak wood contributed gallic acid to the extract, which was absent in cherry wood, but protocatechuric acid was only detected in cherry wood extracts. In experiments on model wines [50], it was demonstrated that the ageing of these wines with oak wood chips resulted in concentrations of total phenolic compounds that were more than four times higher than those observed in wines aged with cherry wood and almost nine times higher than those observed in wines aged with apple wood. However, in the same experiments with real grape wine, the differences were no longer so pronounced. In some types of wine, the differences in total polyphenol content were not statistically significant. In most of the trials, oak wood chips contributed approximately 5% higher levels of total polyphenols, while cherry and apple wood chips contributed approximately 2%. Another study [51] demonstrated that wines matured with oak and cherry wood chips had similar levels of total polyphenols. In the present study, the differences were more pronounced, but the experiments were conducted on apple wine, which contains fewer total polyphenols than grape wines. The results gained after the maturation of wines with apple wood chips were higher than those matured with cherry wood, similar to the study by [PERSON] et al. [50]. No studies have yet been conducted on the use of maple wood chips for wine maturation, but this wood does not contribute more phenolic compounds to wines than apple wood. The polyphenic compounds extracted from wood during the ageing of wines are primarily ellagitannins, including castalagin, vescalagin and grandinin, as well as roburin (A, B, C, D and E) [15; 52]. Their quantity diminishes with increasing toasting levels [40; 43; 53], which may explain the outcomes observed in the present study for samples matured with oak chips. Samples aged in barrels exhibited a significantly higher amount of polyphenic compounds (Table 2), which was attributable to the much longer barrel ageing time and, above all, to the surface area of the wine in contact with the wood. This was many times greater for such small barrels than for wood chips. The antioxidant activity of wines matured with wood chips from different wood species was found to be closely correlated with the content of polyphenic compounds, with a correlation coefficient of 0.99.