## Results and Discussion  
### Volatile Profile of Different Peach Cultivars Using GC-MS  
#### 3.1.1 The Construction of VOCs Profiling for Eight Peach Cultivars  
By searching the NIST database and the chemical standard, a total of seventy VOCs were tentatively identified and quantified for eight peach cultivars using GC-MS. They were categorized into ten groups, including nine aldehydes, ten esters, eleven terpenoids, nine alcohols, six lactones, five ketones, five alkanes, eleven aromatic hydrocarbons, two furans and two other compounds (Figure 2, Table 2). Twenty-three VOCs were commonly identified in all cultivars, including hexanal, nonanal, benzaldehyde, 2-hexenal, butyl acetate, hexyl acetate, linalool, \(\beta\)-myrcene, D-limonene, 1-hexanol, 3-hexenol, 2-hexenol, 2-ethyl-1-hexanol, \(\gamma\)-octalactone, \(\delta\)-decalactone, \(\gamma\)-hexalactone, \(\gamma\)-decalactone, \(\gamma\)-dodecalactone, \(\beta\)-ionone, 2-octanone, 2-ethylfuran and 2,4-ditert-butyl phenol. More than 40 VOCs were identified in HJML (44), DTML (42), HH (42) and JC (43). Fewer than 35 volatile compounds were identified in XFML (35), JXIU (29), JXIANG (35) and JG (32). Seventeen unique compounds were identified only in one cultivar. Differences were observed in the total content of volatile compounds among the eight peach cultivars (Table 2 and Figure 2). Aldehydes were regarded as one of the most significant contributors to the peaches' green and grassy flavor, and have been reported to exist widely in immature plums, apples and pears [19; 20]. The aldehydes detected in this experiment include hexanal, nonanal, benzaldehyde, 2-hexenal, 3-hexenal, (E)-2-nonenal, (E)-2-hexenal, (E)-2-heptenal and heptanal (Table 1). Among these, hexanal, nonanal, 2-hexenal and benzaldehyde were identified as major components and were detected in all the samples, which is consistent with previous studies [20; 21]. Notably, the highest content of 2-hexenal among all samples was 5132.24 \(\mathrm{\SIUnitSymbolMicro kg}\) in HH, while the lowest was 589.96 \(\mathrm{\SIUnitSymbolMicro kg}\) in HJML; therefore, this compound may be the most important factor responsible for the differences in aldehydes among the samples. It is also clear from Figure 2 that the total content of aldehydes is highest in HH and lowest in HJML. Alcohols are a group of compounds other than aldehydes that give peach fruit a green aroma. In this study, nine alcohols were found, namely 2-ethyl-1-hexanol, 3-methyl-3-nonanol, carbitol, 3-hexenol, hexanol, 2-hexenol, 3-methyl-3-buten-1-ol, \(\alpha\)-terpineol and geraniol. Among them, 3-hexenol, hexanol, 2-hexenol and 2-ethyl-1-hexanol were detected in all samples at high levels (Table 2). JC had the highest level of alcohols and JXIANG had the lowest (Figure 2). Figure 2: The total contents of each category of VOCs in eight peach cultivars. 3.1.2 Cluster Analysis of VOCs of eight peach cultivars. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Component**} & \multicolumn{1}{c}{**CAS**} & \multicolumn{1}{c}{**Identification**} & \multicolumn{1}{c}{**XJML**} & \multicolumn{1}{c}{**HAML**} & \multicolumn{1}{c}{**DTML**} & \multicolumn{1}{c}{**HH**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} & \multicolumn{1}{c}{**JML**} \\ \hline
**Latence** & 100+97 & MS, BP, SP4 & 31.82 + 2904 & 152.72 + 5823 & 57.2 + 2.36b & 30.87 + 1.45b & 14.66 + 1.60d  
Esters are the main flavor components of most ripe fruits and provide the fruity notes, and particularly (Z)-3-hexen-1-yl acetate and hexyl acetate are considered to contribute significantly to the aroma characteristics of peaches [6; 22; 23]. A total of ten esters were detected in the eight peach cultivars.