## 3 Results and Discussion
### Effects of Different Sterilization Treatments on the Sensory Quality
#### 3.6.4 GC-MS Analysis
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**NO**} & \multirow{2}{*}{**Ret. Time**} & \multicolumn{6}{c}{**Concentration (ug/L)**} & \multirow{2}{*}{**CAS**} & \multirow{2}{*}{**RI**} \\ \cline{3-3} \cline{5-8}  & & **Compounds** & **Control Group** & **CTS** & **TS** & **TS** & **TSN** \\ \hline
29 & 22.833 & D-Limonene & 7.28 \(\pm\) 0.095 a & 7.92 \(\pm\) 0.081 a & 7.82 \(\pm\) 0.749 a & 7.42 \(\pm\) 0.252 a & 5989-27-5 & 1018 \\
30 & 23.08 & Bis(2-chloro-1-methylethyl) & 3.22 \(\pm\) 0.079 a & 2.66 \(\pm\) 0.082 b & 2.09 \(\pm\) 0.015 c & 2.20 \(\pm\) 0.165 c & 108-60-1 & 1016 \\
31 & 23.193 & 1,1’-exoyls 3-chloro-Propane & 1.15 \(\pm\) 0.006 a & 0.94 \(\pm\) 0.015 b & 0.77 \(\pm\) 0.117 c & 0.92 \(\pm\) 0.032 b & 629-36-7 & 1144 \\
32 & 24.013 & gamma-Terpinene & 1.20 \(\pm\) 0.049 b & 1.68 \(\pm\) 0.031 a & 0.82 \(\pm\) 0.046 c & 0.75 \(\pm\) 0.076 c & 998-45 & 998 \\
33 & 24.433 & 3.7-dimethyl-Decane & 0.57 \(\pm\) 0.006 a & 0.55 \(\pm\) 0.072 a & 0.48 \(\pm\) 0.032 b & 0.56 \(\pm\) 0.010 a & 17312-54-8 & 1086 \\
34 & 29.1 & Decanal & - & 1.51 \(\pm\) 0.378 a & - & 0.57 \(\pm\) 0.087 b & 112-31-2 & 1204 \\
35 & 37.703 & 3,5-bis(1,1-dimethylethyl)-Fhenol & 6.54 \(\pm\) 0.411 b & 8.89 \(\pm\) 0.092 a & - & 1138-52-9 & 1555 \\
36 & 37.71 & 2.4-Di-tert-butylphenol & - & - & 9.29 \(\pm\) 0.240 a & 7.33 \(\pm\) 0.270 b & 96-76-4 & 1555 \\ \hline \hline \end{tabular} Note: The compounds were identified by comparison of retention indices and the mass spectrum with those of NIST library. Retention indices relative to C\({}_{6}\)-C\({}_{2}\) n-alkanes on the DB-1 MS column. Volatiles are shown according to their order of appearance in the chromatogam on the DB-1 MS column—represents not detected. Values with different letters in the same column are significantly different (\(p<0.05\)) from each other.  
\end{table} 
Table 2: _Cont._A total of 36 volatile compounds were identified in 4 different groups of grape juices, with 7 species of alcohols, 2 species of terpenes, 8 species of esters, 5 species of aldehydes, 2 species of ketones, and 2 phenols as well as other ethers, hydrocarbons, and acids. In general, the volatile compounds and their concentrations were significantly different in different sterilization groups. A total of 26 volatile compounds were identified in CK, of which 3-methyl-4-oxopentanoic acid was the main component, accounting for 61.57% of the total volatile compounds, followed by aldehydes, accounting for 20.01% of the total volatile compounds; the dominant aldehydes were hexanal (5.70%) and (E)-2-hexanal (14.31%). In addition, the types and contents of esters and alcohols also affected the aroma characteristics of grape juice to a certain extent. Table 2 shows that the main alcohols and esters in grape juice are ethanol, isopropyl alcohol, and hexenol and its isomers, including 1-hexanol as well as isopropyl acetate, butanoic acid, ethyl ester, (E)-2-butenoic acid, ethyl ester and hexanoic acid, ethyl ester, etc. This profile is similar to that in previous studies [49; 50]. However, the terpene and hydrocarbon compounds in grape juice identified in this study are inconsistent with those reported in the literature [49; 50], which might be due to the different grape varieties, origin, ripeness, and detection method. As shown in Table 2, 31, 28, and 31 volatile components were identified in the CTS, TS, and TSN groups, respectively. On the whole, the main components of the terpenes, alcohols, and esters (such as ethanol, 3-methyl-4-oxopentanoic acid, hexanal, (E)-2-hexanal, 1-hexanol, hexanoic acid, and ethyl ester) in CK were significantly higher than those in other three groups, which indicated that the sterilization methods in this experiment significantly reduced the contents of the main volatile components in the grape juice. Similar conclusions were also observed in [PERSON] et al. [51]. In addition to the reduction in the contents of the main volatile components, sterilization treatment also resulted in the formation of some new substances.