## 2 Results and Discussion
### Profiling of Volatile Compounds in Sweet Potato  
#### 2.4.1 Identification of Volatiles in Sweet Potato  
Four sweet potato cultivars with different flavor (Table 1 in Appendix A) were selected and subjected to GC-MS analysis under the optimized experimental parameters. The volatile compounds identified in the four sweet potato cultivars are shown in Table 1. The ANOVA analysis illustrated the significant differences among the volatile profiles of the different cultivars. In total, 68 volatile compounds were identified in these four cultivars by the mass spectra matched to NIST2017 with a match quality score \(\geq\) 80, among which 28 compounds have been reported in baked sweet potato [10; 36; 37; 38] and the other 40 volatile compounds were identified for the first time in sweet potato. Around 80% compounds in each cultivar produced a RSD value below 20%, indicating that the optimized method has satisfactory repeatability. According to their chemical structure, identified compounds were classified as aldehydes (21), alcohols (13), terpenes (eight), ketones (11), acids (three), phenols (two), alkanes (two), esters (two), furan (one), ethers (one), and others (four).  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Class** & **RT**\({}^{1}\) & **RI**\({}^{2}\) & **Compound** & **CAS** & **MF**\({}^{3}\) & **ID** & **Floor** & **Odor Thresholds** & & & **Relative Content (wig/g)\({}^{4}\)** & \\  & & & & & & & & & & **depth**\({}^{18}\) & **Anna** & **Jiebush95-16** & **Ayamusaki** & **Shuangai** \\ \hline \hline Aldehydes & 3.44 & 676 & Portland & 000110-63.3 & CSHHO & MS,RI & almost, malt, & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Identification of volatile compounds in the four sweet potato cultivars.  
The number and classes of identified volatile compounds and their relative concentrations in the different cultivars varied. In total, 48, 45, 47, and 42 volatile compounds were identified in Anna, Jieshu95-16, Ayamurasaki, and Shuangzai, respectively. The number of volatile compounds in each chemical class in the four cultivars are demonstrated in Figure 3. Aldehydes were the most numerous volatile compounds followed by alcohols, ketones, terpenes, and acids, contributing to around 90% of the volatile compounds of sweet potato. The numbers of aldehydes in the four cultivars were similar while Anna and Ayamurasaki had enriched alcohols. Furthermore, a significantly higher number of terpenes were identified in Anna. Jieshu95-16 and Shuangzai presented similar compositions of volatile compounds classes, and both showed higher levels of ketones and acids. The relative quantitative results showed that Anna contained significantly higher concentration of alcohols, terpenes, and acids while Jieshu95-16 and Shuangzai showed a significant higher content of aldehydes and Shuangzai showed a higher content of ketones. The concentration of different class of compounds in Ayamurasaki was moderate (Table 2).  
Figure 3: Classes of volatile compounds in the four sweet potato cultivars (Anna, Jieshu95-16, Ayamurasaki, and Shuangzai).