# Effects of Table Grape Cultivars on Fruit Quality and Aroma Components
## 3 Results and Discussion
### Aroma Profiles of Different Table Grape Varieties
The contents of C6 compounds in _Italia_, _Manicure Finger_, and _Ruby Seedless_ were higher than 2000 ug/L. The content of (E)-2-hexenal was the highest, followed by hexanal, hexanol, and (Z)-2-hexenol, while the content of 3-hexenol and 3-hexenal was lower. Levels of (E)-2-hexenal in all varieties were higher than levels of 3-hexenal, which is consistent with the findings of [PERSON] et al. [29]. This result illustrates that, in most plants, compounds with a (3Z)-aldehydes structure are rapidly isomerized by (3Z, 2E)-aldehydes isomerase to form the (2E)-aldehydes [30]. The alcohols detected in this study included heptanol, octanol, nonanol, benzyl alcohol, phenylethyl alcohol, 1-octen-3-ol, and 2-ethyl hexanol. The proportion of alcohols in total  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Aroma**} & \multicolumn{5}{c}{**Grape Varieties**} \\ \cline{3-8}
**Compounds** & **Aroma Type** & \multicolumn{2}{c}{**Jumeigui**} & **Shine-Muscat** & **Hutai \# Hao** & **Heiseliancai** & **Zitianwue** & **Summmer Black** \\ \hline Linalool & & \(139.53\pm 0.15\,^{\ast}\) & \(10.04\pm 1.05\,^{\text{h}}\) & \(19.82\pm 1.30\,^{\text{i}}\) & - & \(20.13\pm 0.22\,^{\text{i}}\) & - \\ \hline Neral & Grass & \(11.78\pm 1.36\,^{\text{a}}\) & \(17.51\pm 1.11\,^{\text{i}}\) & - & - & - & \(5.48\pm 0.06\,^{\text{h}}\) \\ \hline Geranial & \multirow{2}{*}{Rose} & \(10.86\pm 0.24\,^{\text{i}}\) & \(1.44\pm 0.03\,^{\text{i}}\) & \(6.72\pm 0.20\,^{\text{h}}\) & \(17.67\pm 1.32\,^{\text{i}}\) & \(7.03\pm 0.06\,^{\text{g}}\) & \(1.91\pm 0.01\,^{\text{i}}\) \\ \cline{2-8} \cline{5-8}  
aroma content was not high, and the content of alcohols in all varieties did not exceed 30 \(\upmu\)g/L. Phenylethyl alcohol and 2-ethyl hexanol were found in high concentrations in the 17 grapes, particularly in _Meixiangbao_, _Zaoheihao_, and _Sweet Sapphire_. However, the alcohol had a high threshold of odor inactivation and did not produce the expected floral aroma. The esters detected in this study were ethyl acetate, ethyl butyrate, ethyl heptanoate, ethyl pentanoate, ethyl 2-methylbutyrate, ethyl 3-methylbutanoate, and ethyl hexanoate. The content of ethyl acetate was the highest, and the ethyl acetate had a considerable celery flavor. However, the deactivation threshold was approximately 4700 \(\upmu\)g/L, without a significant effect on the overall aroma of the grape. The activity threshold of ethyl 2-methylbutyrate and ethyl 3-methylbutanoate was less than 1 \(\upmu\)g/L, and the fruity aroma can be expressed by both of them. Ethyl 2-methylbutyrate and ethyl 3-methylbutanoate contribute significantly to the aromas of _Hutai 8 hao_, _Heibaladuo_, _Sunnmter Black_, _Ruby Seedless_, and _black beet_ varieties. Among them, aldehydes and esters were the main volatile components of _Hutai 8 hao_, which is consistent with [PERSON] et al. [31]. Most of the organic acids in grapes are produced through the long-term respiration of the green plants before the color change of the berries, and most of them are found in the peel and seeds. In this study, _Sunnmter Black_, _Jumeigui_, _Hutai 8 hao_, and _Black beet_ belonging to the _Kyoho_ grapevine series were used due to their advantages including large fruit, bright color, and disease resistance. These cultivars occupy the largest acreage in China. In addition, esters were detected in the four cultivars of the Kyoho grape series, consistent with the results of [PERSON] et al. [14]. In the experiment, only three types of organic acids were detected: hexanoic acid, nonanoic acid, and 2-hexanoic acid. Although the detected organic acids produced unpleasant odors, such as putrefaction and perspiration, they contributed little to the overall aroma. The terpene aroma compounds measured in this study were the most abundant among all the aroma compounds. Our findings show that the terpenes are the characteristic compounds of the four varieties of Muscat grape, consistent with the findings of [PERSON] et al. [15]. Terpene forms the basis of the classification of grape cultivars [14].