## 3 Discussion  
### Oenological Parameters of Apple Wines  
During fermentation, yeasts metabolise sugars present in the apple must, synthesising mainly ethanol, carbon dioxide and other by-products that determine the quality of wines [30]. The quantity of ethanol in wine is primarily influenced by the initial amount of sugars present in the setting, originating from the fruit and added during the technological process. The alcohol content is also influenced by the yeast strain employed, the temperature at which the fermentation process occurs and the quantity of sulphur dioxide utilised [31]. The alcohol content of the analysed apple wines, aged with wood chips of varying tree species, with differing degrees of toasting, ranged from 11.52 to 11.57% (Table 1). The results obtained were not statistically different (\(p>0.05\)). Similar results were obtained for other works on similar topics [32; 33; 34; 35; 36; 37]. The lack of change in alcohol concentration after ageing wines with the addition of wood chips is positive and expected. It is reasonable to assume that a small addition of wood chips and wine ageing in tightly sealed vessels will not contribute to a loss of wine strength. On the other hand, the decrease in alcohol concentration in barrel-aged wines is completely natural. The extended maturation period of wines and the porous nature of oak wood contribute to the occurrence of micro-losses of alcohol, which is commonly referred to as the \"angel's share\" [38; 39]. In dry wines, the optimal taste profile, free from the perceived shortcomings of a \"hollow taste\", is largely influenced by the sugar-free extract. This extract is comprised of glycerol, which contributes to the velvety aftertaste observed in fermented beverages due to its oily consistency. Additionally, glycerol plays a role in the viscosity of wines, which can be observed in the glass as the liquid flows down the walls, leaving characteristic \"tears\" that form a \"crown\" [40]. The extract content of wines aged in the presence of wood chips from different wood species ranged from 2.95 to 3.00 g/L, with no statistically significant differences observed. The degree of toasting of wood chips also showed no effect  
Figure 1: Sensory analysis (QDA) of the apple wines aged in barrel (B) or with the addition of various wood chips (Ch—cherry wood chips, A—apple wood chips, O—oak wood chips, M—maple wood chips; 1—lightly toasted, 2—medium-toasted, 3—heavily toasted); n = 5; STD <5%. on extract content (Table 1). In the study by [PERSON] et al. [35], the authors demonstrated that, regardless of the degree of toasting of the wood chips, maturation in oak barrels or maturation in tanks without the addition of wood, the wines exhibited no significant increase or decrease in the total extract. [PERSON] et al. [37] and [PERSON] et al. [41] have reported that the addition of oak chips to wines and barrel ageing do not significantly affect total extract content. The present study demonstrated an increase in total extract content in barrel-aged wines (Table 1). This may be attributed to the extraction of compounds, primarily polyphenolic compounds, from the surface of the barrels and the loss of alcohol observed with barrel ageing. The evaporation of some volatile compounds results in a thickening of the extract, thereby increasing its concentration. The total acidity of wines is primarily derived from tartaric, malic, lactic and citric acids. They originate mainly from fruits but are also formed during the fermentation of wines [42]. According to the legal regulations in Poland [43], the total acidity in fermented fruit beverages should range from 3.5 g to 9 g of malic acid per litre. All apple wines matured in the presence of wood chips met this requirement. No statistically significant differences were found in the total acidity of wines matured with wood chips from different wood species and with different degrees of burnout (Table 1). [PERSON] et al.