## 2 Results
In terms of the contents performed, it was notable that 3-methyl-butanoic acid (No. 44), hexanoic acid (No. 47), phenylethyl alcohol (No. 10) and 2-methyl-1-butanol (No. 3) were abundant in both BT and WT, whereas 2-methylpropanoic acid (No. 42) was only abundant in BT and benzyl benzoate (No. 58) in WT. Moreover, hexanal (No. 18), benzeneacetaldehyde (No. 28), benzaldehyde (No. 27), 2,4-di-tert-butylphenol (No. 15), 1-octen-3-ol (No. 8) and acetoin (No. 38) were also present at relatively higher levels in both samples, while 5-ethylcyclopent-1-enecarboxaldehyde (No. 25), (_E_)-2-octenal (No. 26) and 1-pentanol (No. 4) were more abundant in BT. As shown in Figure 3, although the same components were identified, they were distinguished in terms of contents. Besides, according to the outcomes using \(t\)-tests, five kinds of compounds showed significant differences between BT and WT in terms of the concentration, and the results are shown in Figure 3. The volatiles included 1 aldehyde, 3 acids and 1 sulfur-containing compound. In addition, it should be noted that 24 kinds of compounds were identified only in BT, while 13 compounds only in WT. In general, the compounds detected in both samples at different levels together with those detected in BT, but not in WT, or _vice versa_, must play an important role in distinguishing the overall volatile profiles of the two samples. The corresponding aroma description and threshold values of these compounds (42 in total) are shown in Table 2. Besides, the PCA of these compounds was performed based on their concentrations, and the results are shown in Figure 4. The two principle components (PC1 and PC2) accounted for 90.20% of the whole variance (79.97% and 10.23%, respectively). The PCA result of the two samples showed that BT and WT could be clearly separated on the PCA plot. It could be seen that BT was located on the positive side of the PC1 dimension and kept separate from the sample cluster of WT. Additionally, the major compounds contributing to the positive dimension of the PC1 component included dodecanal (No. 29), acetophenone (No. 39), benzophenone (No. 40), 1-hexanol (No. 6), (_E_)-9-octadecenoic acid ethyl ester (No. 55) and dibenzofuran (No. 65). In contrast, major compounds contributing to the negative dimension of the PC1 component included octanoic acid (No. 49), 3-methyl-1-pentanol (No. 5), \(\beta\)-ethylphenethyl alcohol (No. 12), 3-methyl-2-butenal (No. 22), 3-methyl-2-butenoic acid (No. 45), 4-methylpentanoic acid (No. 46),furyl hydroxymethyl ketone (No. 63), methional (No. 67), (methylthio)-cyclohexane (No. 68), (_Z_)-2-butenal (No. 17) and 3-methylthio-1-propanol (No. 69). Moreover, the important compounds on the positive side of PC2 included propanoic acid (No. 41), 2-methyl-2-butenal (No. 19), 5-ethylcyclopent-1-enecarboxaldehyde (No. 25) and 2-butanol (No. 1). For the negative side of PC2, butanoic acid (No. 43), heptanoic acid (No. 48), isobornyl acetate (No. 53), dihydro-5-methyl-2(3_H_)furanone (No. 61) and 3-(methylthio)propanoic acid (No. 70) were the main contributors. Figure 4: Principle component analysis (PCA) score plot: (**a**) BT and WT samples; (**b**) the compounds detected in both samples with a significant difference and those detected in BT, but not in WT, or _vice versa_ (numbers correspond to Table 1). Figure 3: Contents of volatile compounds detected in BT and WT: (**a**) volatiles classified by chemical families; (**b**) volatiles with a significance value lower than 0.05 (No. 25: 5-ethylcyclopent-1-enecarboxaldehyde; No. 48: heptanoic acid; No. 49: octanoic acid; No. 50: nonanoic acid; No. 70: 3-(methylthio)propanoic acid).