# Influence of Apple Juice Type on Fermentation Process and Volatile Compounds of Hard Apple Cider
## 3 Results and Discussion  
### Physico-Chemical Properties of Juices and Ciders  
Traditional beverages such as ciders have always been popular among variously aged populations, but recent years have brought them closer to younger consumers via commercially available products. However, there is a difference between apple juices that can be found on the market. Many apple juices are actually diluted syrups with added sweeteners such as aspartate, sorbitol, etc. Such sweetening agents are not available for yeast to ferment to alcohol. Thus, the premise of this investigation was to assess the possibility of alcohol formation during the fermentation of two different apple juices, onebeing cloudy 100% apple juice and the other being clear apple juice made from apple syrup with added sugars. The starting parameter (original extract) for both juices was determined at the beginning of fermentation and is shown in Table 1. Sample 1 contained 13.2 \({}^{\circ}\)P and Sample 2 contained 12.9 \({}^{\circ}\)P. According to the statistical analysis, this was not a significant enough difference between the extract content to influence the process of fermentation. The content of fermentable sugars (original extract) is in accordance with previous research [13]. In case there was a significant difference between original extracts among samples, it could be easily diluted to the same value using demineralized water. The fermentation for Sample 1 lasted for 10 days, while fermentation for Sample 2 lasted a bit longer, 14 days. However, the 4-day difference between samples was statistically significant and influenced the formation of volatile compounds. A shorter fermentation time for Sample 1 was probably due to the added sugar, which is visible through the original extract (1.053). This resulted in higher alcohol content in Sample 1 (8.4%\(\upsilon\)/\(\upsilon\)). Sample 2 had a slightly lower extract, and thus lower ethanol content, resulting with 7.8%\(\upsilon\)/\(\upsilon\) of ethanol in the final product. The extract was totally spent during fermentation, resulting in 0.941 in Sample 1 and 0.946 in Sample 2. The final apple cider was thus extra dry, leaving a sour taste in the mouth, similar to dry wine. Dryness is usually recognized as a sour taste and occurs when all of the sugar from the pomace is spent during fermentation. Dryness is actually one of the main sensory characteristics of apple cider and is related to the number of residual sugars after fermentation [6]. Apple juice is naturally rich in monosaccharides such as glucose and fructose, which are easily metabolized by yeast. Since Sample 1 was produced with only 50% of apple juice, sucrose was added to sweeten it, which resulted in a higher ethanol amount, as the disaccharide, sucrose, is also easily fermented by yeast. Since both juices are commercially available on the market, they were subjected to industrial pasteurization. For this experiment, both samples were inoculated with the same amount of yeast for cider to obtain aseptic conditions for yeast to thrive. Table 2 presents a follow-up of the fermentation process via the most important parameters: original gravity, final gravity, and alcohol by volume. Fermentation vessels were stored the same temperature and inoculated with the same amount of the same yeast. The only difference was the juice type. Fermentation in Sample 1 had a much faster pace and lasted for 10 days. The end was evident by the final extract dropping to 0.946. Fermentation in Sample 2 was slower and lasted for 14 days. This was probably due to the nature of the sugars, namely, Sample 1 contained added sugars, while Sample 2 only had sugars originating from apples, and this caused the yeast to act faster in Sample 1.