# Discovery and Flavor Characterization of High-Grade Markers in Baked Green Tea
## 2 Results and Discussion
### Odor Composition Analysis and Aroma Extract Dilution Analysis  
SPME combined with two-dimensional comprehensive gas chromatography-olfactometry-mass spectrometry analysis (GC\(\times\)GC-O-MS) was used to analyze the odor components in the different grades of baked green tea. A total of 34 odor compounds (specifically, 13 aldehydes, 6 esters, 4 ketones, 7 alcohols, 2 terpenoids, and 2 phenolic compounds) were identified in the 19 kinds of tea samples; 32 volatile compounds were identified in the different grades of H tea; 25 volatile compounds were identified in the different grades of T tea; and 28 volatile compounds were identified in the different grades of S tea. Through the calculation of the retention index (RI), the National Institute of Standards and Technology (NIST) database search, and an aroma extract dilution analysis (AEDA) [23], 22 odor active compounds were identified, including 2-methyl butyraldehyde, valeraldehyde, hexanal, (E)-2-pentenal, heptanal, (E)-2-octenal, furfural, (E,E)-2-4-heptalenal, benzaldehyde, \(\beta\)-cyclodextrin, butyl hexanoate, cis-3-hexenyl hexanoate, ethyl acetate, (E)-methyl geranate, 1-penten-3-one, linalool, 3-octanol, hotrienol, \(\alpha\)-terpineol, phenylethyl alcohol, \(\beta\)-myrcene, and D-limonene. The odor compounds were extracted by SPME, and the contribution of each odor compound to each type of baked green tea was obtained by an odor dilution analysis of the odor active compounds in the three kinds of baked green tea samples via the AEDA method. The AEDA analysis revealed that the compounds contributing to the odor components of the three baked green teas were similar in composition, as shown in Table 12, thus rendering the odor profiles of the three green teas similar. A higher FD factor indicates a greater contribution to the overall odor [24; 25]. It can be seen that linalool and \(\beta\)-myrcene, both with FD factors \(\geq\)27, are the compounds with the greatest odor contribution and have been shown to be the high-boiling-point compounds responsible for the formation of chestnut-like and flowery odors in the baking process [26; 27]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample 1** & **Market Grade 2** & **Abbreviation** & **Score 3** & **Grade 4** \\ \hline \multirow{8}{*}{H tea} & Best Class & H-1 & 92 \(\pm\) 0.3 & A \\  & Super class Grade A & H-2 & 96 \(\pm\) 0.5 & A \\  & Super class Grade B & H-3 & 85 \(\pm\) 0.2 & B \\  & Super class Grade C & H-4 & 82 \(\pm\) 0.4 & B \\  & Super class & H-5 & 83 \(\pm\) 0.3 & B \\  & First class Grade A & H-6 & 75 \(\pm\) 0.8 & C \\  & First class Grade B & H-7 & 76 \(\pm\) 0.9 & C \\  & Second class & H-8 & 72 \(\pm\) 0.4 & C \\ \hline \multirow{8}{*}{T tea} & Best Class & T-1 & 93 \(\pm\) 0.1 & A \\  & Super class Grade A & T-2 & 87 \(\pm\) 0.5 & B \\  & Super class Grade B & T-3 & 84 \(\pm\) 1.1 & B \\  & Super class & T-4 & 74 \(\pm\) 0.3 & C \\  & First class & T-5 & 73 \(\pm\) 0.2 & C \\ \hline \multirow{8}{*}{S tea} & Super class Grade A & S-1 & 94 \(\pm\) 0.2 & A \\  & Super class Grade B & S-2 & 83 \(\pm\) 0.7 & B \\  & First class & S-3 & 74 \(\pm\) 0.4 & C \\ \cline{1-1}  & First class Grade A & S-4 & 75 \(\pm\) 0.6 & C \\ \cline{1-1}  & First class Grade B & S-5 & 72 \(\pm\) 0.3 & C \\ \cline{1-1}  & First class Grade C & S-6 & 78 \(\pm\) 0.2 & C \\ \hline \end{tabular} \({}^{1}\) H tea: Huangshan Maofeng; T tea: Taiping Houkui; S tea: Shucheng Xiaolanhua. 2 The quality of each tea worsens from top to bottom. For example, “Best Class” is the best and “Second Class” is the worst with respect to H tea. 3 A total of 13 evaluators have made evaluation from a 100-point scale (0–100 points), and each sample score was averaged. 4 According to the five factors of tea evaluation in China National Standard “Methodology for sensory evaluation of tea” (GB 23776-2018), different market grades of teas were divided into Grades A, B, and C (i.e., “Jiaji”, “Yiji”, and “Bingji”, which denote high-grade, middle-grade, and low-grade, respectively).  
\end{table}