# Characterization of the Aroma of an Instant White Tea Dried by Freeze Drying
## 2 Results and Discussion
### Aroma Reconstruction and Omission Experiments  
The 16 aroma-active compounds were identified via GC-MS-O analysis (Table 2). Only 15 of them (except hotrienol) were used to prepare the reconstruction model (FM1) according to their concentrations (Table 1). As shown in Figure 2A, FM1 and the SDE extract were detected to have similar aroma profiles, indicating the 15 volatiles are major aroma-active compounds of the SDE extract. In addition, FM1 and the SDE extract showed slight differences in aroma intensities in floral and roasted notes (\(p<0.05\)), which might be ascribed to the lack of hotrienol. Meanwhile, there might be some compounds that could affect the aroma profile have not been identified yet, in view of researchers have shown that volatile compounds below the threshold concentrations can sometimes exert a remarkable influence on the overall aroma [32]. Recently, comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC \(\times\) GC-TOFMS) has been shown to analyze aromatic contributors with advantages of high separation, fast data acquisition rate, wide linear dynamic range and full-range mass sensitivity [4]. Further, GC \(\times\) GC-TOFMS coupled with sensory analysis are to be used to conduct further analysis.  
The perception of an aroma compound is a complex process and affected by many factors, such as volatility, concentration, antagonism and synergism between aroma compounds [12; 32]. For investigating how the volatiles affected the overall aroma profiles, three aroma active compounds, i.e., linalool ( floral note), _trans-_\(\beta\)-damascenone (sweet note) and camphene (green note) were chosen to do omission test from FM1, because these compounds had the highest FD factor (FD = 64) among all the detected volatiles and possessed different notes. FM2, FM3 and FM4 were designed to omit the linalool, _trans-_\(\beta\)-damascenone and camphene from FM1, respectively. As shown in Figure 2B, in comparison to FM1, FM2 showed decreased intensities in the floral note (5.2 vs. 3.8) (\(p<0.05\)) and sweet note (5.0 vs. 4.7), as well as the increased intensity of woody note (2.4 vs. 2.9). FM3 that was the model prepared by the omission of _trans-_\(\beta\)-damascenone from FM1, showed decreased intensities in sweet (5.0 vs. 3.8) (\(p<0.05\)), floral (5.2 vs. 4.9) and fruity (2.5 vs. 2.1) notes, as well as slight increase in green note intensity (3.6 vs. 3.8). FM4 that was the model prepared by  
Figure 2: Aroma reconstruction (**A**) and aroma omission (**B**) based on GC-MS-O and OAV analyses of the SDE extract. FM1 was the aroma reconstruction model; FM2 was prepared by omitting 128.7 mg/L of linalool ( floral) from FM1; FM3 was prepared by omitting 5.9 mg/L of _trans-_\(\beta\)-damascenone (sweet) from FM1; FM4 was prepared by omitting 42.1 mg/L of camphene (green) from FM1. In Figure 2A, SDE extracts and FM1 samples showed significant difference (\(p<0.05\)) in floral and roasted notes; in Figure 2B, FM1 and FM2 samples showed significant difference (\(p<0.05\)) in floral note, FM1 and FM3 samples showed significant difference (\(p<0.05\)) in sweet note, FM1 and FM4 samples showed significant difference (\(p<0.05\)) in green note.  
omission of camphene from FM1, showed decreases in the green (3.6 vs. 2.9) (\(p<0.05\)) and roasted (1.7 vs. 1.4) notes, as well as increased intensity in floral note (5.2 vs. 5.4). These results indicated that linalool, _trans_-\(\beta\)-damascenone and camphene could affect the aroma not only through contributing the respective characteristic notes, but also via synergism interactions.