## 3 Results and Discussion
### Volatile Profiles of Fruits in Four Different Apricot cultivars  
It is known that volatile compounds play a dominant role in contributing to the overall flavor of fruits. HS-SPME-GC-MS/MS was used to detect volatile compounds in four different apricot cultivars (Figure S1). A total of 63 volatile compounds were identified from the four apricots. According to their functions, compounds were grouped into 14 alcohols, 6 acids, 6 esters, 15 aldehydes, 13 ketones and 9 terpen (Table S1). These volatile classes were considered to be the central components that distinguished plums from apricots [32; 33]. The result was different from a previous study that found 208 volatile substances in 14 apricot cultivars from the Xinjiang region [5]. In this study, the total content of volatiles in the YOU apricots was the highest, followed by the LPH, DBY and XB apricot varieties (Figure 1a). Moreover, it was observed that the composition of volatile compounds was different among the four apricot varieties (Figure 1b). The proportion of terpen in DBY, YOU and LPH apricots was relatively higher among overall compounds. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Apricot** & \multicolumn{3}{c}{**Soluble Sugars (mg/g FW)**} \\ \cline{2-4}
**Cultural** & **Fructose** & **Sorbitol** & **Glucose** & **Sucrose** \\ \hline DBY & 9.85 \(\pm\) 0.65 b  & 4.47 \(\pm\) 0.15 c  & 12.18 \(\pm\) 1.67 c  & 42.49 \(\pm\) 1.51 c  \\ LPH & 15.84 \(\pm\) 2.10 a  & 10.43 \(\pm\) 0.23 a  & 24.82 \(\pm\) 2.58 b  & 63.02 \(\pm\) 3.52 b  \\ YOU & 9.52 \(\pm\) 0.96 b  & 6.27 \(\pm\) 0.69 b  & 13.44 \(\pm\) 0.50 c  & 30.92 \(\pm\) 2.02 d  \\ XB & 16.58 \(\pm\) 0.93 a  & 11.04 \(\pm\) 0.72 a  & 28.89 \(\pm\) 2.85 a  & 77.58 \(\pm\) 5.36 a  \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The composition and content of soluble sugars in four different apricot cultivars. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Apricot** & \multicolumn{4}{c}{**Organic Acids (mg/100 g FW)**} \\ \cline{2-4}
**Cultural** & **Quinic Acid** & **Malic Acid** & **Ascorbic Acid** & **Citic Acid** & **Succinic Acid** \\ \hline DBY & 49.58 \(\pm\) 2.30 a [FOOTNOTE:a]Footnote a: The different superscripts in the column mean significant differences (\(p<0.05\), Duncan’s test) for different apricot cultivars. Values are presented as mean \(\pm\) standard deviation (\(n=3\)It was noteworthy that alcohols and aldehydes were the dominant volatile compounds in XB apricots, which led to considerable differences between XB apricots and the other three apricot samples. The results suggested that the composition and content of volatiles clearly varied in different apricot varieties. However, there were still 12 volatiles that occurred in all four apricot cultivars (Figure 2). In addition, the alcohol compounds with a high concentration were ethanol and 1-dodecanol, which were present in all four apricots (Table S1). The concentrations of ethanol and 1-dodecanol were more than 2.00 ug/kg in all apricot cultivars except 1-dodecanol in XB apricots. It is worth mentioning that 2-decen-1-ol, 1-octanol, myrcenol, nonanol and 2_4_-dimethyl-cyclohexanol were only found in the LPH, XB, LPH, XB and YOU cultivars, respectively. Interestingly, no acids in the XB apricots were detected, but they were generally present in the other three apricots. The ester compound with the highest level was ethyl acetate, with an excess of 21.00 ug/kg in LPH apricots. It has been reported that the maximum content of hexanal in some apricot cultivars was 1475.30 ug/kg [34]. In this work, the highest concentration of hexanal was only 2.37 ug/kg in DBY apricots. Another C6 aldehyde (i.e., 2-hexenal) was detected at a higher level. The content of 2-hexenal exceeded 12.00 ug/kg in the four apricots. Those C6 compounds were considered  
Figure 1: The content (**a**) and relative composition (**b**) of volatile compounds in four different apricot cultivars. DBY, Dabaiyou apricot; LPH, Luopuhongdaike apricot; YOU, You apricot; XB, Xiaobai apricot.