## 4 Discussion  
### Volatile Aroma Composition  
As to the authors' knowledge, this is the first study to report the volatile profile from Honeycrisp juices. Substantiating our results, esters, aldehydes, and alcohols have been reported as major groups of volatile compounds in juices from different apple cultivars including McIntosh (17), Jonagold (13), Golden Delicious, Red Delicious (18), Holsteiner Cox, Ingrid Marie, and Rajka (19). Our results indicated quantitative and qualitative differences in the level of volatile compounds between the two cultivars. Esters are known for their desirable aromatic notes in apple beverages, which are often described as \"fresh apple\", \"fruity\", and \"sweet\", and it is reasonable to assume that the higher amount of total esters in Honeycrisp juices would increase its overall aroma and flavor (20). The higher content of 2-methyl-4-pentenal in McIntosh juice samples could offer desirable green grass and fruit aroma notes (15). Despite the greater content of total esters in Honeycrisp juices, the higher level of ethyl acetate in Honeycrisp juices may lead to the development of undesirable flavor as excessive amounts  
\begin{table}
\begin{tabular}{c l c c c c c} \hline \hline \multirow{3}{*}{**Treatment Combinations**} & \multicolumn{4}{c}{**Normalized Peak Area Counts \({}^{\text{a}}\)**} \\ \cline{3-7}  & \multicolumn{2}{c}{**2-Methyl-4-**} & \multicolumn{2}{c}{**(E)-2**} & \multicolumn{2}{c}{**Branched Chain**} & \multicolumn{2}{c}{**(Z)-2**} & \multicolumn{2}{c}{**Ethanol**} \\  & & **Pentenal** & **Hexenal** & **Achool** & **Hexen-1-olololololol**} & \\ \hline \multirow{3}{*}{Harvest (H)} & Comm. b  & 6.62 \(\pm\) 0.103  & 1.02 \(\pm\) 0.133  & 1.07 \(\pm\) 0.017  & 1.33 \(\pm\) 0.184  & 0.56 \(\pm\) 0.113  \\  & Late & 4.57 \(\pm\) 0.103  & 0.51 \(\pm\) 0.141  & 1.11 \(\pm\) 0.018  & 1.61 \(\pm\) 0.195  & 0.71 \(\pm\) 0.119  \\
1-MCP (M) & 1-MCP & 5.22 \(\pm\) 0.107  & 0.70 \(\pm\) 0.137  & 0.39 \(\pm\) 0.018  & 1.52 \(\pm\) 0.189  & 0.17 \(\pm\) 0.116  \\  & Control & 5.81 \(\pm\) 0.107  & 0.74 \(\pm\) 0.137  & 3.69 \(\pm\) 0.018  & 1.41 \(\pm\) 0.189  & 1.09 \(\pm\) 0.116  \\  & CA  (A) & 4.64 \(\pm\) 0.107  & 0.93 \(\pm\) 0.137  & 0.58 \(\pm\) 0.018  & 1.97 \(\pm\) 0.189  & 0.50 \(\pm\) 0.116  \\  & RA  & 6.52 \(\pm\) 0.107  & 0.56 \(\pm\) 0.137  & 2.23 \(\pm\) 0.018  & 0.97 \(\pm\) 0.189  & 0.77 \(\pm\) 0.116  \\  & Clear & & 3.37 \(\pm\) 0.107  & 0.54 \(\pm\) 0.137  & 0.66 \(\pm\) 0.018  & 0.92 \(\pm\) 0.189  & 0.41 \(\pm\) 0.116  \\  & Cloudy & 8.98 \(\pm\) 0.107  & 0.96 \(\pm\) 0.137  & 1.88 \(\pm\) 0.018  & 2.02 \(\pm\) 0.189  & 0.86 \(\pm\) 0.116  \\  & Comm. & 1-MCP & 5.59 \(\pm\) 0.146  & 0.85  
of fermentation volatiles, including ethyl acetate, which can generate off-flavors and aromas [3]. The higher concentration of butanoate esters in McIntosh juices could provide juice with a favorable fruity, ripe, and sweet aroma [2]. Due to the low odor threshold values (Table 2) of acetate and butanoate esters, these groups of esters could generate a significant contribution to the final aroma of the juice samples. Accordingly, it has been demonstrated that acetate esters, including butyl acetate, 2-methyl butyl acetate, hexyl acetate, and ethyl butanoate, are major contributors to the typical apple-like aroma and flavor in many apple cultivars [21; 22]. Similarly, hexyl acetate, butyl acetate, and ethyl butanoate were reported as the most important volatiles in Jonagold juice [23]. In addition to straight-chain esters, a branched-chain ester, 2-methyl butyl acetate, was one of the most abundant volatile compounds detected in Honeycrisp and McIntosh juices. Owing to its lower threshold value, 2-methyl butyl acetate has been described as one of the most significant odor active volatile compounds in other apple cultivars, including Gala [24]. It has been indicated that C-6 aldehydes, particularly (E)-2-hexenal and hexenal, are responsible for the fresh green aroma in apple juice [25].