## 3 Results and Discussion
### Compositions of Volatile Compounds  
Primarily, a total of 120 volatile compounds were detected by GC-MS analysis of 18 distilled _soju_ extracted with SPME fiber. Among them, 56 volatile compounds detected in more than 6 samples are listed in Table 4 according to their chemical classes, relative concentrations, and Kovats indices (KIs), including 31 esters, 11 alcohols, 1 acid, 4 aldehydes, 3 ketones, and 6 miscellaneous compounds. Esters and alcohols were the largest classes among  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Code** & **pH** & **Total Acidity (as Acetic Acid, \% \(\
u\)/\(\
u\))** & **Total Soluble Solids (\({}^{\circ}\)Brix)** & **Lactic Acids (mg/L)** \\ \hline CTO & 4.33 \(\pm\) 0.03  & 0.09 \(\pm\) 0.01  & 16.20 \(\pm\) 0.00  & 375.39 \(\pm\) 0.58  \\ DJA & 4.84 \(\pm\) 0.06  & 0.08 \(\pm\) 0.00  & 8.10 \(\pm\) 0.00  & 8.28 \(\pm\) 0.36  \\ GSO & 5.60 \(\pm\) 0.02  & 0.04 \(\pm\) 0.00  & 14.70 \(\pm\) 0.00  & 114.39 \(\pm\) 1.19  \\ HBI & 3.90 \(\pm\) 0.04  & 0.29 \(\pm\) 0.06  & 14.70 \(\pm\) 0.00  & 435.06 \(\pm\) 2.37  \\ HGO & 6.31 \(\pm\) 0.14  & 0.02 \(\pm\) 0.00  & 15.20 \(\pm\) 0.00  & 66.44 \(\pm\) 1.84  \\ HWA & 4.65 \(\pm\) 0.03  & 0.08 \(\pm\) 0.02  & 14.90 \(\pm\) 0.00  & 486.02 \(\pm\) 2.58  \\ IDO & 4.48 \(\pm\) 0.02  & 0.09 \(\pm\) 0.02  & 15.20 \(\pm\) 0.00  & 156.09 \(\pm\) 1.99 \\ IPU & 4.82 \(\pm\) 0.21  & 0.06 \(\pm\) 0.01  & 14.90 \(\pm\) 0.00  & 53.86 \(\pm\) 2.37  \\ JRO & 7.24 \(\pm\) 0.06  & 0.02 \(\pm\) 0.00  & 9.73 \(\pm\) 0.06  & 41.40 \(\pm\) 0.71  \\ JWA & 4.33 \(\pm\) 0.02  & 0.09 \(\pm\) 0.02  & 9.70 \(\pm\) 0.00  & 35.40 \(\pm\) 0.38  \\ MBA & 4.27 \(\pm\) 0.06  & 0.10 \(\pm\) 0.03  & 14.67 \(\pm\) 0.06  & 590.88 \(\pm\) 1.10  \\ MIR & 7.30 \(\pm\) 0.05  & 0.02 \(\pm\) 0.00  & 14.90 \(\pm\) 0.00  & 108.48 \(\pm\) 0.31  \\ MSO & 3.62 \(\pm\) 0.02  & 0.31 \(\pm\) 0.06  & 159.03 \(\pm\) 0.06  & 1610.70 \(\pm\) 5.86  \\ OAK & 4.04 \(\pm\) 0.05  & 0.09 \(\pm\) 0.01  & 10.27 \(\pm\) 0.06  & 117.10 \(\pm\) 0.21  \\ PIU & 4.38 \(\pm\) 0.07  & 0.09 \(\pm\) 0.02  & 15.03 \(\pm\) 0.06  & 397.35 \(\pm\) 2.45  \\ R25 & 7.42 \(\pm\) 0.02  & 0.02 \(\pm\) 0.00  & 9.90 \the quantified volatiles. The two most abundant volatile compounds were ethyl octanoate and ethyl decanoate, accounting for 31.41% and 31.02% of the total quantified volatiles. In addition, ethyl dodecanoate (6.39%), ethyl hexanoate (4.62%), isoamyl acetate (2.15%), 1-pentanol (11.88%), and phenylethyl alcohol (2.28%) were major volatiles in 18 samples. These compounds were also major volatiles in various alcoholic beverages [5; 20; 21]. R40 (738.16 mg/L), which was atmospherically distilled using 100% sweet potato, retained the highest total quantified volatile compounds, followed by MSO (720.32 mg/L) made under atmospheric distillation of non-glutinous rice, and DJA (482.88 mg/L), which was vacuum distilled using rice. A total of 31 esters were detected among the 18 samples. Esters have a big influence on the aroma characteristics of alcoholic beverages with strong fruit-related notes [30]. Ethyl octanoate described as a sweet and fruity aroma [31] and ethyl decanoate described as a floral and sweet odor [32] were the two most frequently detected compounds among the 18 samples, and in particular, MSO and R40, which were atmospherically distilled, showed much higher levels of these compounds. In addition, isoamyl acetate, 2-phenylethyl acetate, ethyl heptanoate, and diethyl butanedioate were identified as major compounds. Among the various esters detected in this study, isoamyl acetate with a banana-like flavor [33], ethyl acetate having a sweet and fruity hint [34], and 2-phenylethyl acetate described as a rose or apple-like odor [35] are considered potent fruity compounds, which are also found in various distilled _soju_, beers, _cheongju_, and rice wines [36; 37; 38]. Alcohols are major compounds that give various aroma characteristics to liquor along with esters [36]. In the case of alcohol compounds, unlike the esters, the differences among samples were not large.