## 2 Results and Discussion  
### Identification of Volatile Compounds in Strawberries  
Figure 1 shows a representative GC chromatogram of CO\({}_{2}\)-treated bright-red strawberries after 9 d of storage. Thirty volatiles (5 aldehydes, 17 esters, 3 ketones, 2 alcohols, 2 acids, and 1 furanone) were identified (Table 1). Among the identified compounds,  
\(11\) volatile compounds (hexanal, 2-hexenal, nonanal, benzaldehyde, methyl acetate, methyl hexanoate, ethyl hexanoate, ethyl octanoate, 2-heptanone, butyric acid, and hexanoic acid) were identified by comparing them with the retention time and mass spectra of authentic standards. In previous studies, methyl butanoate, ethyl butanoate, methyl hexanoate, ethyl hexanoate, and 4-methoxy-2,5-dimethyl-3-(2H)-furanone were reported as characteristic volatiles of strawberries [20; 21].  
At day 0, some volatiles occurred or were present in higher concentrations only in the bright-red strawberries. For example, (_2E_)-hexenyl acetate was not present in half-red strawberries but was present in bright-red strawberries at day 0. (_2E_)-Hexenyl acetate was also reported in seven _Fragaria_\(\times\)_ananassa_ cultivars by [PERSON] et al. [20]; however, it was not present in the 'Camarosa' and 'Chandler' strawberries harvested in India [22]. Thus, the volatile composition of strawberries may be affected by the cultivar type, maturity, and/or agricultural practices, such as the growing region. [23].  
During cold storage, (_2E_)-hexenyl acetate and ethyl octanoate were newly produced in half-red and bright-red strawberries, respectively. The volatile composition of strawberries during cold storage was affected by the ripening stage when harvested. For example, ethyl octanoate was not found in fresh strawberries (day 0) during the two ripening stages; however, it was produced only in bright-red strawberries after cold storage, regardless of CO2 treatment. Previous studies found that ethyl octanoate was not present in strawberries of the 'Cigaline', 'Chandler', 'Albion', and 'Festival' cultivars [24; 25; 26]. [PERSON] et al. reported that ethyl octanoate is formed after 5 d of storage in 'Hong Yan' strawberries [27]. The concentrations of some volatiles decreased or were absent after CO2 treatment. For example, the acetaldehyde content decreased, and 2-butanone was absent in bright-red strawberries after CO2 treatment.  
Figure 1: A representative GC chromatogram of CO2-treated bright-red strawberries after 9 d of storage at 10 \({}^{\circ}\)C. Volatile compound codes are provided in Table 1.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Peak on.** & **Vitalite Compound** & **Olate Description\({}^{\bullet}\)** & \multicolumn{2}{c}{**DB-WAX Column**} & \multicolumn{2}{c}{**DB-SMS Column**} & \multicolumn{1}{c}{**Entacted line (\(\mathbf{k}\mathbf{p}^{\prime}\mathbf{p}^{\prime}\))**} & \multicolumn{1}{c}{**Internal Standard**} & \multicolumn{1}{c}{**Component Newly**} \\ \cline{2-10}  & & **Unknown RI** & **Literature \(\mathbf{k}\mathbf{p}^{\prime}\)** & **Unknown RI** & **Literature \(\mathbf{k}\mathbf{p}^{\prime}\)** & **Internal BL** & **Storage** \\ \hline \hline \multirow{2}{*}{_Alkyloids_} & \multirow{2}{*}{Actisaldehyde} & \multirow{2}{*}{Acetisaldehyde} & \multirow{2}{*}{P