## 2 Results
### Aroma Profile of the Ripe Berries of Two Varieties of Grapes
#### 2.1.1 Free-Form Aroma Compounds in Two Varieties  
Table 1 displays the concentrations of free-form aroma compounds in commercially harvested 'Marselan' and 'Merlot' grapes. Out of the 42 components, 22 aroma compounds showed higher concentrations in the 'Marselan' grapes compared to the 'Merlot'. These compounds include seven C6/C9 compounds, three straight-chain aliphatics, four aromatic compounds, six terpenes, and two norisoprenoids. Notably, the concentrations of the majority of C6/C9 compounds in the 'Marselan' grapes were approximately 2-3 times higher than those in the 'Merlot'. In particular, (_E_)-2-hexen-1-ol and (_Z_)-3-hexen-1-ol reached levels that were approximately about 5 times and 63 times higher, respectively. Although C6/C9 compounds, also known as green leaf volatiles (GLVs), have a typical \"grass flavor\", \"green leaf flavor\" and other characteristics [13; 22], their direct contribution to red wine aromas is limited. This is because they can be rapidly conversed during fermentation and have high sensory thresholds.  
Terpenes and norisoprenoids exhibit significant varietal differences, with a greater variety of free-form components found in 'Marselan'. Furthermore, 'Marselan' grapes were found to contain \(\alpha\)-terpinene, \(\gamma\)-terpinene, terpinolene, and \(\alpha\)-ionene, which were not detected in 'Merlot'. With the exception of L-menthol, the levels of aroma compounds detected in both varieties were significantly higher in 'Marselan' grapes. Notably, (_E_)-\(\beta\)-damascenone was the most abundant isoprenoid-derived aroma compound in both varieties, with a concentration in 'Marselan' approximately three times higher than that in 'Merlot'. Grape-derived terpenes and norisoprenoids significantly contribute to the varietal typicality of wine, providing floral and citrus, tropical fruit and violet aromas, respectively [3]. The difference in terpenes and norisoprenoids between 'Marselan' and 'Merlot' grapes may potentially affect aroma characteristics of their respective wines.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Aroma Components**} & \multirow{2}{*}{**Retention**} & \multirow{2}{*}{**Standards**} & \multirow{2}{*}{**Quantitative Methods**} & \multicolumn{2}{c}{**Concentrations (ug/kg)**} \\ \cline{3-5}  & & & & **Masselan** & **Merlot** \\ \hline \hline C6/C9 compounds & & & & & \\
1-Hexanal & 1090.2 & Hexanal & A.Q. & 6271.59 \(\pm\) 821.86 *** & 3793.55 \(\pm\) 302.11 \\
3-Hexenal & 1142.1 & Hexanal & R.Q. & 439.67 \(\pm\) 51.74 ** & 191.92 \(\pm\) 35.84 \\ (_E_)-2-Hexenal & 1227.4 & (_E_)-2-Hexenal & A.Q. & 8507.44 \(\pm\) 929.72 ** & 4190.59 \(\pm\) 316.91 \\
1-Hexen-3-ol & 1247.3 & (_Z_)-3-Hexenol & R.Q. & 21.85 \(\pm\) 3.12 & 13.12 \(\pm\) 8.58 \\
1-Hexanol & 1349.2 & 1-Hexanol & A.Q. & 392.91 \(\pm\) 22.53 * & 138.11 \(\pm\) 21.36 \\ (_Z_)-3-Hexen-1-ol & 1381.7 & (_Z_)-3-Hexenol & A.Q. & 592.3 \(\pm\) 49.64 ** & 9.28 \(\pm\) 1.54 \\
1-Nonanal & 1397.9 & Nonanal & A.Q. & 2.64 \(\pm\) 0.39 & 2.01 \(\pm\) 0.46 \\ (_E_)-2-Hexen-1-ol & 1402.4 & (_E_)-2-Hexenol & A.Q. & 1031.45 \(\pm\) 288.38 ** & 298.84 \(\pm\) 42.68 \\ (_E_)-2,4-Hexadienal & 1410.5 & (_E_),Z_)-2,6-Nonadien & R.Q. & 53.54 \(\pm\) 6.01 ** & 30.33 \(\pm\) 2.61 \\ (_E_)-2-Nonneal & 1543.1 & (_E_)-2-Nonneal & A.Q. & 0.30 \(\pm\) 0.05 & 0.29 \(\pm\) 0.01 \\ (_E_)-2,6-Nonadienal & 1594.8 & (_E_),Z_)-2,6-Nonadien & A.Q. & 1.17 \(\pm\) 0.23 & 1.08 \(\pm\) 0.15 \\
1-Nonanol & 1659.3 & 2-Nonanol & R.Q. & 0.25 \(\pm\) 0.03 & 0.22 \(\pm\) 0.05 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of free-form aroma compounds between ‘Marselan’ and ‘Merlot’ grapes.