## 2 Results and Discussion
### Partial Least Squares Analysis Further Verifies the Relationship between Aroma Compounds and Notes  
As shown in Table 4, generic descriptive analysis and a ten-point line scale of sweet orange according to the aroma intensity were performed by six sensory panelists. Aromas of sweet orange were profiled with fresh, green, fruity, fatty, citrus, floral, peely and woody notes. Through the three replicates of sensory evaluation, obvious differences were found among the notes in the five sweet oranges. PLRS was applied to certify the correlation between the concentrations of aroma compounds detected by GC-MS and mean score of notes by sensory evaluation. The 49 odor-active compounds were used as X-matrix, and the 8 sensory notes were Y-matrix, which generated the correlation load diagram of PLRS, as shown in Figure 2. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Compounds A**} & \multirow{2}{*}{**Thescholds**} & \multirow{2}{*}{**Literatures B**} & \multicolumn{4}{c}{**OAV (C/D) C**} & \multirow{2}{*}{**Note OAV**} & \multirow{2}{*}{**Note OAV**} & \multirow{2}{*}{**Note OAV\% E**} \\ \cline{5-10}  & & & & **ZG** & & **MS** & & **YY** & **YX** & **QY** & \\ \hline
1 & acetaldehyde & 0.01 & 1 & 41 & -D & - & - & 34 & fresh 37.15 & 6.02 \\
2 & hexanal & 0.0091 & 2 & 6 & 6 & 8 & 7 & 5 & green & \\
3 & hexanol & 0.161 & 2 & - & \(<\)1 & 1 & 1 & - & 6.51 & 1.06 \\
4 & ethyl propionate & 0.1 & 3 & - & \(<\)1 & \(<\)1 & - & 1 & & \\
5 & ethyl isobutyrate & 0.015 & 3 & - & - & - & - & 5 & \\
6 & ethyl butyrate & 0.02 & 3 & 40 & 5 & 28 & 6 & 233 & fruity & \\
7 & ethyl\(\,\)2\(\,\)methylbutyrate & 0.002 & 3 & - & 14 & 16 & - & 186 & 193.56 & 31.39 \\
8 & ethyl isovalerate & 0.006 & 3 & - & - & - & - & 8 & \\
9 & ethyl caproate & 0.005 & 3 & 28 & 14 & - & - & 72 & \\
10 & nonanal & 0.015 & 2 & - & - & - & - & 1 & fatty 1.804 & 0.31 \\
11 & octanal & 0.012 & 2 & - & 2 & - & \(<\)1 & 2 & & \\
12 & a-pinene & 0.19 & 2 & \(<\)1 & \(<\)1 & \(<\)1 & 1 & & \\
13 & 3-carene & 0.044 & 2 & \(<\)1 & - & \(<\)1 & 1 & \(<\)1 & & \\
14 & myrcene & 0.0166 & 2 & 90 & 37 & 28 & 64 & 38 & & \\
15 & a-terpinene & 0.085 & 2 & - & 3 & 2 & 1 & \(<\)1 & citrus & \\
16 & limonene & 0.2 & 2 & 122 & 96 & 107 & 114 & 109 & 280.31 & 45.47 \\
17 & 4-terpineol & 0.005 & 2 & - & 2 & - & - & - & - & \\
18 & o-Cymene & 0.4 & 2 & 5 & 6 & 2 & 2 & \(<\)1 & & \\
19 & \(\alpha\)-Terpinolene & 0.041 & 2 & - & - & - & 3 & - & \\
20 & 4-Isopropyl toluene & 0.0133 & 2 & 139 & 146 & 138 & 64 & 46 & & \\
21 & linalool & 0.0015 & 2 & 136 & 73 & 30 & 44 & 10 & floral 58.42 & 9.48 \\
22 & heden & 5.7 & 2 & 1 & 1 & - & - & - & - & \\
23 & decanal & 0.001 & 4 & 66 & 33 & - & 22 & - & peel 40.23 & 6.53 \\
24 & trans-caryophyllene & 0.06 & 5 & 2 & - & 12 & 3 & 6 & woody 7.07 & 1.15 \\
25 & germacene & 0.016 & 5 & 1 & - & - & - & - & \\ \hline \hline \end{tabular} Numbers 1–5 listed in the Literature column mean that thresholds of the compounds were detected by: 1, [PERSON] and [PERSON] (1997); 2, [PERSON] et al. (2001); 3, [PERSON] et al. (1988); 4, [PERSON] et al. (1997); 5, [PERSON] et al. (1987), according to ref [(22)]. A The volatile compounds with OAVs \(\geq\) 1. B The odor threshold (\(\mu\)g/g) calculated in water referred to in the literature. C The OAV of each volatile compound. D not detected. E Percentage contribution of notes in sweet orange.  
\end{table} 
Table 3: Average OAV value and aroma note percentage of volatile compounds in sweet orange. Figure 1: The notes contour of sweet orange flavor (the percentage of aroma notes was larger in the inner concave, but smaller in the outer convex and sharp one).