# Influence of Apple Juice Type on Fermentation Process and Volatile Compounds of Hard Apple Cider
## 3 Results and Discussion
### Volatiles Analysis of Ciders  
As a general rule of thumb, the slower the fermentation and maturation, the better the product; this can be applied in any fermentation process. Namely, formation and changes in volatile compound concentrations during maturation and aging are the most important aroma and taste influences. Another important stage in producing high-quality cider is the aging process. Here are some points on how to understand the difference between maturation and aging. According to [PERSON] [17; 18], maturation is the time it takes cider or wine to become ready to drink. Maturation is the point when a cider is ready, while aging can be defined as the additional time cider is left to sit after it becomes ready. During this time, many compounds change their concentration, resulting in rounded aromas and taste. A set of volatile compounds detected in the fermented cider were followed up for three weeks during the maturation period. The list of all of the analyzed compounds is presented in Table 3.  
Aging reduces the fruity esters commonly found in cider that are considered to be young or which have not aged for long. During the aging period, fruity aromas are transformed into spicier and phenolic notes. [PERSON] [18] suggested the most important volatile compounds in cider; some of them affect the cider aroma positively, and some add unpleasant characteristics. In general, they are divided into several groups of chemicals [18]: alcohols, organic acids, aldehydes, carbonyls, esters, sulfur compounds, and others (diacetyl; 1,4,5,6-tetrahydro-2-acetopyridine). According to [PERSON] [18], all alcohols are considered desirable and affect aroma positively (ethanol; propan-1-ol; butan-1-ol; isopentan-1-ol; heptan-1-ol; hexan-1-ol; 2- and 3-ethylutan-1-ol; 2-phenylethanol). Malic, lactic, hexanoic acids, acetaldehyde, benzaldehyde, hexanal, ethyl and butyl lactate, ethyl benzoate, ethyl benzoate, ethyl guiaicol, ethyl-2- and ethyl-3-methylbutyrate, ethyl octanoate, ethyl ocenoate, ethyl decanoate, and ethyl dodecanoate as well. Apple aromas are mainly associated with ethyl butanoate and ethyl 2-methylbutanoate [19]. 3-methylbutyl acetate is a component which can be found in distilled spirits [20]. Ethyl hexanoate is a result of the fermentation process and evokes a fruity aroma [21]. Another compound related to apples is 1-butanol, and it is an indicator of maturity [22]. 3-methylbutanol is an important aroma volatile and provides a malty, bitter, alcoholic, or solvent aroma [23], while 1-hexanol gives a fermented profile to ciders. Geranyl acetate adds fruity, rose-like aromas in ciders, similar to 2-phenylethanol and 2-phenylethylly acetate, which gives a floral and rose odor. Benzyl alcohol provides fruity and green odor, while eugenol has a clove- and medicinal-like aroma [24]. \begin{table}
\begin{tabular}{c c c c c c c} \hline Day & Original Extract & Final Extract & Alcohol by Volume (\%) \\ \hline Sample & 1 & 2 & 1 & 2 & 1 & 2 \\
1 & 1.053 \(\pm\) 0.003 & 1.052 \(\pm\) 0.003 & & & 0.0 & 0.0 \\
2 & 1.048 \(\pm\  
This research evaluated 33 aromatic compounds related to cider fermentation and maturation. It is known that maturation and aging for ciders can last from several weeks to two years [25]. The quality and aroma development depend, according to some authors [26; 27], on the type of cider and apple variety, but some authors recognize the effect of fermentation conditions on cider quality [28]. This indicates that some of the aromatic compounds from the apples themselves are lost during fermentation [28]. According to [PERSON] et al. [28], the yeast strain selection is of utmost importance for providing desirable aroma compounds during fermentation and maturation. Namely, they