Hydrolates of apple juice are an important but often underutilized source of aromatic compounds for enhancing the varietal aroma of apple wine. In this master's thesis, we focused on the preparation and characterization of hydrolates from fresh apples and apple juice, and examined the differences and similarities in their composition. The hydrolate samples were qualitatively and semi-quantitatively evaluated using gas chromatography coupled with mass spectrometry. The research was divided into three sections. In the first section, we analyzed the aromatic profile of 'Granny Smith' apples. We found that esters dominate the primary aroma, while aldehydes and alcohols are prevalent in the secondary aroma. Pasteurization of apple juice reduced the content of most aromatic compounds. In the second section, we conducted an experiment involving the alcoholic fermentation of apple must, where volatile aromatic compounds were separated from the apple juice and returned to the must during fermentation. We studied the influence of different yeast growth phases (lag, exponential, stationary, and death phases) on the persistence of added aromatic compounds. The results showed that the content of added alcohols and aldehydes mostly decreased during the course of alcoholic fermentation, especially in the later phases of yeast growth. A similar degradation trend was also observed for esters. In the third section, we investigated the impact of post-fermentation processes, such as cooling, SO2 addition, oak chip usage, and filtration, on the persistence of added aromatic compounds in the wine during maturation. Higher maturation temperatures accelerated the degradation of compounds, while cooling the wine after fermentation slowed down their degradation. The addition of SO2 and oak chips did not significantly affect the final content of volatile compounds in the wine. Filtration had a positive and statistically significant effect at higher maturation temperatures, but overall, it was not effective enough to permanently prevent the degradation process of aromatic compounds in the wine. Nevertheless, the results obtained are important for a better understanding of the mechanisms of apple aroma degradation and for finding solutions to improve the processing of apple wine.
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