# Chemical Composition and Flavor Characteristics of Cider
## 3 Results and Discussion
### Volatile Compounds of Cider fermented with Different Non-Saccharomyces Yeasts  
#### 3.2.1 SPME-GC-MS Analysis of Cider Fermented with Different Non-Saccharomyces Yeasts  
Supplementary Table S1 shows the concentrations of volatile compounds in cider detected by GC-MS. A total of 58 kinds of volatile compounds were detected in the cider samples, including 24 esters, 6 alcohols, 12 acids, 4 aldehydes, 1 ketone, and 11 other compounds. The highest volatile content among them was most types of esters, alcohols, and acids. Our study found several previous important aroma esters identified in ciders, such as hexanoic acid, ethyl ester, octanoic acid, ethyl ester, decanoic acid, ethyl ester, and acetic acid, 2-phenyl ethyl ester [20; 21]. In most of the co-inoculation fermented ciders, several of the esters (except hexanoic acid, ethyl ester) were higher than Sc, which proved \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Samples 1**} & \multirow{2}{*}{**FAJ**} & \multicolumn{5}{c}{**Ciders**} \\ \cline{3-6}  & & **Sc** & **Sc+Zb** & **Sc+Rm** & **Sc+Km** & **Sc+Dh** \\ \hline Glucose (g/L) & 140.00 \(\pm\) 0.00 c & 0.50 \(\pm\) 0.08 a & 0.45 \(\pm\) 0.07 a & 0.30 \(\pm\) 0.00 b & 0.29 \(\pm\) 0.02 b & 0.33 \(\pm\) 0.03 b \\ Alcohol (\%, \(\sigma\)/o) & ND & 10.03 \(\pm\) 0.76 ab & 9.17 \(\pm\) 0.06 b & 10.47 \(\pm\) 0.68 a & 9.37 \(\pm\) 0.29 b & 9.43 \(\pm\) 0.40 b \\ pH & 3.76 \(\pm\) 0.02 d & 3.94 \(\pm\) 0.01 c & 4.06 \(\pm\) 0.02 b & 3.98 \(\pm\) 0.03 a & 4.03 \(\pm\) 0.04 b & 4.03 \(\pm\) 0.05 b \\ TA (g/L) & 5.37 \(\pm\) 0.07 b & 6.40 \(\pm\) 0.33 c & 5.16 \(\pm\) 0.44 b & 5.94 \(\pm\) 0.15 a & 5.28 \(\pm\) 0.09 b & 4.89 \(\pm\) 0.22 b \\ Glycerol (g/L) & 5.97 \(\pm\) 0.36 a & 6.25 \(\pm\) 0.38 a & 6.24 \(\pm\) 0.66 a & 6.48 \(\pm\) 0.36 a & 6.25 \(\pm\) 0.47 a & 6.34 \(\pm\) 0.40 a \\ Total yeast count (log & & & & & & \\ CFU/mL) & ND & 6.79 \(\pm\) 0.01 a & 6.78 \(\pm\) 0.01 a & 6.79 \(\pm\) 0.01 a & 6.19 \(\pm\) 0.04 c & 6.62 \(\pm\) 0.02 b \\ \hline \hline \end{tabular}  
* Results represent the mean \(\pm\) SD for three independent experiments. Different letters represent significant differences at the 95% confidence level (Duncan’s test). ND = not detected. TA = total acid (expressed as a percentage of tartaric acid). Sc, _S. cerevisiae_ monoculture. Sc+Zb, _S. cerevisiae_ and _Z. bailii_ co-inoculation. Sc+Rm, _S. cerevisiae_ and _R. mucilaginous_ co-inoculation. Sc+Km, _S. cerevisiae_ and _K. marxianus_ co-inoculation. Sc+Dh, _S. cerevisiae_ and _D. hansenii_ co-inoculation. FAJ, apple juice.  
\end{table} 
Table 1: Physicochemical parameters of apple juice and cider samples fermented with different non-_Saccharomyces_ yeast. that inoculation with _R. mucilaginousa, D. hansenii_, or _Z. bailii_ could improve the contents of these compounds. Interestingly, (Z)-3-Hexen-1-ol was detected only in FAJ. 3-methyl-1-butanol was relatively abundant in several cider samples, except Sc+Rm and Sc+Km; the difference in content between the groups was great. The material can produce a smell similar to that of nail polish [22]. 2-Furanmethanol (3.91 \(\pm\) 5.53 ug/L) was detected only in Sc+Rm, which has the aroma of coffee and caramel. 1-Dodecanol (3.00 \(\pm\) 4.25 ug/L) was detected only in Sc+Km, which has the aroma of violet. Regarding phenylethyl alcohol, an important aroma component identified in apple wine [23], it can give the cider a rosy aroma [24]; a high concentration was found in cider from co-inoculation fermented groups (except Sc+Km), followed by that from monoculture fermentation. The range of concentration was 488.65-782.68 ug/L and there was a significant difference among the groups. The result was slightly different from previous research, which may be caused by using different species of non-_Saccharomyces_ yeast [5]. Hexanal and furfural were detected only in FAJ, 2,4-dimethyl-benzaldehyde only in Sc+Zb and Sc+Km, and 2,5-dimethyl-benzaldehyde only in Sc and Sc+Zb; no aldehydes were detected in Sc+Dh.