## 2 Results and Discussion
### Calculating OAV Values of Volatile Compounds in Sweet Orange and Percentage of Notes Contribution  
As is shown in Table 3, there were 13, 16, 10, 12 and 16 compounds (OAVs \(\geq\) 1) corresponding to the ZG, MS, JY, YX and QY samples that were considered to contribute significantly to the aroma of the samples. In this study, ethyl butyrate (5-233), myrcene (28-90), limonene (96-122), 4-isopropyltoluene (46-146), linalool (10-136) and decanal (22-66) had relatively higher OAVs, and were powerful aroma compounds in the five sweet orange samples. According to the GC-O olfaction of sensory evaluation panelists and the scores of notes in five sweet orange samples, 25 key aroma substances with OAVs \(\geq 1\) were classified into 8 notes. The fresh note of sweet orange was all derived from acetaldehyde; hexanol and hexanal had a strong aroma of vegetables and grass, so they were classified as green note; all esters contributed to the characteristic fruits note; all terpene compounds, including limonene and terpinene, provided the characteristic aroma for the citrus note; linalool and hetion had the fragrance of roses and jasmine, which were classified as the note of flowers; decanal with long chain carbon had the peculiar aroma of citrus peel; trans-caryophyllene and germacrene had distinct aroma of wood and herbs, which were attributed to the woody note.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**RT**} & \multirow{2}{*}{**Compounds 1**} & \multicolumn{2}{c}{**RI 2**} & \multirow{2}{*}{**Identification 3**} & \multirow{2}{*}{**ZGC**} & \multirow{2}{*}{**Concentration (g/g) MS**} & \multirow{2}{*}{**YY**} & \multirow{2}{*}{**YX**} & \multirow{2}{*}{**QY**} \\ \cline{4-4} \cline{8-9}  & & & **DB-Wax** & & & & & & & \\ \hline A1 & 4.479 & acetaldehyde & 690 & 396 & MS, RI, Std & 0.407 \(\pm\) 0.03 & - & - & - & 0.336 \(\pm\) 0.02 \\ A2 & 5.174 & ethyl acetate & 887 & 610 & MS, RI, Std & 0.171 \(\pm\) 0.009 c 4  & 0.178 \(\pm\) 0.02 c & 0.33 \(\pm\) 0.027 b & 0.17 \(\pm\) 0.03 c & 0.479 \(\pm\) 0.05 a \\ A3 & 5.999 & ethyl propionate & 950 & 725 & MS, RI, Std & - & - & 0.0603 \(\pm\) 0  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**CPomounds 1**} & \multicolumn{2}{c}{**RI 2**} & \multirow{2}{*}{**Identification 3**} & \multirow{2}{*}{**FOOTNOTE:3]Footnote 3: footnotemark: [ENDFOOTNOTE]**} & & & & & & & & & & & & \\ \cline{3-14}  & **DB-Wax & **DB-5** & & & & & & & & & & & & \\ \hline A36 & 21.398  
We can intuitively see the percentage contribution of each note in Figure 1. The percentage contribution of citrus note was 45.57%, accounting for almost half of the whole flavor; the second was the fruity note, with a percentage of 31.39%. Both percentage contributions of the citrus and fruit notes totaled more than 70%, which were the main aroma in sweet orange juice; the floral, peely, fresh, woody, green and fatty notes accounted for 9.48%, 6.53%, 6.02%, 1.15%, 1.06% and 0.31%, respectively. Although they had a smaller percentage contribution of notes in the aroma of sweet orange, they were indispensable. They played roles in modifying the aroma of orange juice and made the aroma more full and rich. The establishment of the note contour of the sweet orange aroma can help flavorists to innovate and develop products related to sweet orange flavor, and help the fragrance companies and customers to quickly and efficiently evaluate and discuss sweet orange flavor in terms of its aroma.