## 3 Results and Discussion
### Identification and Determination of Volatile Compounds in Forty Apple Cultivars
In this study, differences were also observed in the total content of volatile compounds among the 40 apple cultivars, ranging from 2041.27 \(\pm\) 120.36 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW to 27,813.56 \(\pm\) 2310.07 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW (Table 3). Honey Crisps (HC) had the highest content of volatile compounds, followed by Jazz (JZ, 27,493.25 \(\pm\) 3800.46 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW) and RXH (27,015.38 \(\pm\) 2540.92 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW). In contrast, HS had the lowest volatile compound content, followed by COP (2622.09 \(\pm\) 150.74 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW) and Royal Gala (RG, 2919.26 \(\pm\) 351.23 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW). The total content of volatile compounds in Orin (OI, 16,863.94 \(\pm\) 1806.24 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW), Red General (RGL, 15,447.86 \(\pm\) 1120.35 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW), and Envy (EV, 13,286.84 \(\pm\) 1139.54 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW) were 3- to 4-fold greater than those in Granny Smith (GS, 3930.31 \(\pm\) 328.94 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW), Starkrimson (SR, 3784.77 \(\pm\) 327.05 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW), and Fuji (FJ, 3562.94 \(\pm\) 310.02 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW). The above analysis indicates that the volatiles were dependent, to a great extent, on the cultivars, which is consistent with a previous study [18]. Golden Delicious (GD) has been reported to have the high volatile compound content [24]. However, the total content of volatiles in cultivar GD in this study (4436.74 \(\pm\) 425.36 \(\mathrm{\SIUnitSymbolMicro g}\)/kg FW) was not high. This result might be attributed to geographical variations, such as territory, climate, water and other environmental factors. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Code*** & **Compounds** & **CAS No b** & **Odour Description c** & **RT d** & **RI***/RI f** & **Content (\(\mathrm{\SIUnitSymbolMicro g}\)/kg FW)** \\ \hline Ketenes & & & & & & \\ C1 & 1-Penten-3-one & 1629-88-9 & Mushroom & 12.07 & 1022/1020 & 1.45 (0–15.07) \\ C2 & 1-Octen-3-one & 4312-99-6 & Mushroom & 20.22 & 1305/1305 & 3.74 (0–44.64) \\ C3 & 6-Methyl-5-hepten-2-one & 110-93-0 & Earthy, strawberry & 21.26 & 1355/1348 & 3.38 (0–33.26) \\ Acids & & & & & & \\ D1 & 2-Methylbutanoic acid & 116-53-0 & Fatty & 29.37 & 1670/1670 & 38.34 (0–201.97) \\ \hline Others & & & & & & \\ O1 & (E)-2-Pentenal & 1576-87-0 & Green & 15.23 & 1142/1140 & 0.09 (0–3.78) \\ O2 & Dodecane & 112-40-3 & Oily & 16.79 & 1187/1187 & 6.96 (0–127.3) \\ O3 & Tetradecane & 629-59-4 & Oily & 22.49 & 1398/1398 & 30.38 (0–129.62) \\ O4 & Cogene & 3865-25-5 & Wood, terpeny & 25.56 & 1503/1505 & 2.88 (0–20.71) \\ O5 & Hexadecane & 544-76-3 & Oily & 27.59 & 1581/1581 & 12.00 (0–88.67) \\ O6 & Estragole & 140-67-0 & Anise & 29.66 & 1687/1687 & 293.26 (0–2012.56) \\ O7 & \(\alpha\)-Regamote & 1769-05-7 & Green & 30.37 & 1694/1695 & 343.04 (0–191.69) \\ O8 & a-Farnesene & 502-61-4 & Green, oily, fatty & 30.75 & 1725/1754 & 850.09 (0–76.2919.09) \\ O9 & Thiophene & 470-40-6 & Resonous & 31.48 & 1747/1760 & 19.75 (0–97.63) \\ O10 & Anethe & 25679-28-1 & Anise & 32.40 & 1780/1780 & 47.93 (0–492.16) \\ \hline \hline \end{tabular}  
* Compound codes. b CAS number. c Colour description in the literature [25; 26; 27; 28]. d Retention time (min). e Retention index in the HP-INNOWax column. f Retention index in the database ([[http://www.flavournet.org](http://www.flavournet.org)]([http://www.flavournet.org](http://www.flavournet.org)): [[http://webbook.Nist.gov/chemistry](http://webbook.Nist.gov/chemistry)]([http://webbook.Nist.gov/chemistry](http://webbook.Nist.gov/chemistry)), accessed on 13 April 2021) and the literature [19; 25; 26; 27; 28]. FW: fresh weight  
\end{table} 
Table 2: _Cont._  
\begin{table}