## 2 Results
### Identification of Arona Profiles in Citrus Blend Black Tea  
About 800-1000 peaks were initially detected in samples with a minimum S/N ration of 50. After peak alignment, we initially identified 664 common volatile compounds by comparisons with mass spectra in the NIST 2014 library with a minimum similarity of 75%. Subsequently, the retention index (RI, the Kovats index) values of all compounds were calculated and compared with known RI to validate the accuracy of compound identification. The compounds whose RI value had a difference bigger than 20 by compared with the reported were deleted. Finally, 348 volatile compounds were ultimately identified as Reliable. These comprised 60 esters, 55 alkenes, 45 aldehydes, 45 ketones, 37 alcohols, 20 aromatic hydrocarbons, 20 oxyheterocyclic compounds, 19 nitrogen-containing compounds, 18 alkanes, 15 ethers, 7 phenols, 5 acids, 1 sulfur-compound, and 1 alkyne (Supporting Information Table S2). Moreover, some important volatile compounds were verified by comparison with standards.  
The distribution of the volatiles compounds in the citrus blend black teas is shown in Figure 1. The ratio (%) of alkenes was the highest (49.77% (CG); 47.16% (BG); 41.05% (LG)). Aldehyde was the second abundant compound classification with obvious differences existed in content levels among the three groups, that the contents in LG (26.31%) was twice higher than BG (11.20%). Ester was the third larger composition in CG (17.00%) and BG (16.82%); while ester (7.19%) was near with aromatic hydrocarbon (7.33%) in LG. The ranges of alcohol and aromatic hydrocarbon were 4.85-8.86% and 5.91-10.70%, respectively. The distribution of oxyheterocyclic compounds significantly differed among the three groups, being 6.24% in LG, but low in CG (0.22%) and BG (1.02%).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Group** & **No.** & **Brand** & **Origin** & **Ingredient** & **Score** & **Description** \\ \hline \multirow{4}{*}{Citrus group (CC)} & CG-1 & LUPICIA-Jyo no Kaori & Japan & Black two, Toy citrus post & 4.90 & Slightly two flavor, Citrus-like, \\  & CG-2 & TWININGS-Orange \& Crammon Teo & Poland & Black two, cinnnnnnnnnnnnnnnnn  
In detail, limonene was absolutely the highest constituent (CG, 35.41%; BG, 26.10%; LG, 29.44%), followed by \(\beta\)-myrcene (CG, 4.75%; BG, 5.73%; LG, 4.25%). Benzaldehyde was the main aldehyde, which was reported in many famous Chinese black teas, and considered as a key aroma compound in them contributing floral odorant [17; 18]. \(p\)-Cymene, a common aromatic hydrocarbon in nature, with various biological activities, was detected in a high level (CG, 2.82%; BG, 6.93%; LG, 5.80%). Linalool, which is considered the most important odorant in most black teas [7; 19], was also identified in blend teas at high ratios of 1.59-4.20%.  
In addition to the above common higher-content components, different distribution of aroma profile was also exhibited among the three types. In CG, decanoic acid ethyl ester (6.95%), octanoic acid ethyl ester (4.74%), decanal (2.73%), \(o\)-cymene (1.94%) and ethyl butyrate (1.60%) took higher portions. \(\alpha\)-terpineol (3.12%), \(\beta\)-pinene (1.58%), geranyl acetate (6.06%), _cis_-\(\beta\)-ocimene (4.90%), neryl acetate (2.93%), and sabinene (2.72%), were highly identified in BG. Neral (7.79%), furfural (4.23%), benzeneacetaldehyde (3.54%), 2-hexenal (2.94%), (E,E)-2,4-heptadienal (1.83%), geranyl acetate (1.75%), \(\alpha\)-terpineol (1.74%), linalool (1.59%), and \(\alpha\)-farnesene (1.40%) were identified in extracts at ratios \(>\)1% in LG.