## 3 Results and Discussion
### Active Odorants  
The odor thresholds of the aroma compounds detected in Shine Muscat grapes and their odor activity values are presented in Table 3. A total of 44 volatile aroma compounds (10 alcohols, 6 aldehydes, 1 ester, 5 ketones, and 22 monoterenes) were detected in Shine Muscat grape berries using GC/MS analysis. Among them, only eight compounds, (\(E\))-2-hexen-1-ol, 1-hexanol, (\(Z\))-3-hexenal, (\(E\))-2-hexenal, hexanal, (\(E\))-linalo oxide, (\(E\))-\(\beta\)-damascenone, and linalool, were found to be active odorants (OAV > 1). Thus, these eight volatile compounds seemed to be key aroma compounds responsible for the overall aroma characteristics of grape berries. However, the other compounds with OAV less than 1 and glycosidic aroma compounds could affect the aroma characteristics. For example,  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & \multirow{2}{*}{**Aroma Compounds**} & \multirow{2}{*}{**1**} & \multirow{2}{*}{**RI**} & \multicolumn{6}{c}{**Weeks After Full Bloom**} \\ \cline{6-9}  & & & **12** & **14** & **16** & **18** & **20** & **22** \\ \hline \multirow{9}{*}{Alcohol} & 2-Ethyl-1-hexanol & 1510 & 4.0(0.3) \({}^{\circ}\) & 4.4(0.2) \({}^{\circ}\)k & 4.7(0.3) \({}^{\circ}\)b & 5.4(0.1) \({}^{\circ}\) & 5.4(0.3) \({}^{\circ}\) & 4.6(0.2) \({}^{\circ}\)k \\  & 1-Hephenol & 1472 & 0.30(0.03) \({}^{\circ}\)b & 0.5(0.1) \({}^{\circ}\) & 0.4(0.1) \({}^{\circ}\)b & - & - & - \\  & 1-Hexanol & 1373 & 168.6(65.2) \({}^{\circ}\)d & 366.9(18.8) \({}^{\circ}\) & 724.3(18.4) \({}^{\circ}\)b & 938.7(56.1) \({}^{\circ}\) & 653.8(98.6) \({}^{\circ}\) & 403.1(39.5) \({}^{\circ}\) \\  & (\(E\)-2)-Hexen-1-ol & 1426 & 294.7(79.6) \({}^{\circ}\)d & 893.6(41.1) \({}^{\circ}\)a & 623.1(84.0) \({}^{\circ}\)b & 439.2(28.5) \({}^{\circ}\) & 279.1(48.7) \({}^{\circ}\) & 279.5(19.9) \({}^{\circ}\) \\  & (\(E\)-3)-Hexen-1-ol & 1382 & - & 90.0(0.3) \({}^{\circ}\)b & - & 30.0(0.2) \({}^{\circ}\)b & 0.8(0.1) \({}^{\circ}\) & 0.5(0.1) \({}^{\circ}\) \\ Alcohol & (\(Z\))-3-Hexen-1-ol & 1400 & 33.1(1.4) \({}^{\circ}\)c & 42.9(0.3) \({}^{\circ}\)b & 54.2(5.) \({}^{\circ}\)b & 45.1(3.1) \({}^{\circ}\)b & 29.1(0.6) \({}^{\circ}\) & 173.1(0.4) \({}^{\circ}\) \\  & 1-Nomanal & 1679 & 0.2(0.01) \({}^{\circ}\)b & 0.1(0.01) \({}^{\circ}\)b & 0.1(0.01) \({}^{\circ}\)b & 0.1(0.03) \({}^{\circ}\)b & 0.1(0.002) \({}^{\circ}\) & 0.1(0.01) \({}^{\circ}\) \\  & (\(E\)-2)-Hepten-1-ol & 1529 & - & 0.1(0.01) \({}^{\circ}\)b & 0.1(0.01) \({}^{\circ}\)b & - & - & - & - \\  & 1-Octanol & 1577 & 0.5(0.03) \({}^{\circ}\)b & 0.6(0.1) \({}^{\circ}\)b & - & - & 0.30(0.08) \({}^{\circ}\)b & 0.5(0.1) \({}^{\circ}\) \\  & 1-Octanol-3-ol & 1472 & 0.1(0.02) \({}^{\circ}\)b & 0.2(0.04) \({}^{\circ}\)b & 0.2(0.02) \({}^{\circ}\)b & 0.1(0.03) \({}^{\circ}\)b & 0.1(0.03) \({}^{\circ}\) & 1.0(0.03) \({}^{\circ}\) \\  & (\(E\)-2)-Pentent-ol & 1335 & - & 0.5(0.04) \({}^{\circ}\)b & 0.3(0.  
aroma glycosides undergo hydrolysis by \(\beta\)-glucosidase in the mouth, enhancing the fruit flavor [28]. The OAV of (E)-2-hexen-1-ol, the only active compound representing the fruity scent, tended to decrease with ripening, while 1-hexanol with an herbal scent was highest in berries harvested at 22 WAFB. The OAVs of aldehyde compounds, including (_Z_)-3-hexenal, (_E_)-2-hexenal, and hexanal, responsible for green and herbaceous scents, were relatively higher than those of other volatile compounds. The OAVs of linalool and its derivative (linalool oxide furanoid), representing a floral scent, tended to increase with ripening. (_E_)-\(\beta\)-Damascenone, a floral volatile, is an important active odorant primarily contributing to the flavor of Shine Muscat grape despite its presence in very low to trace amounts due to its very low odor threshold (0.002 ug/L in water). This result is in agreement with that of a previous report [18].