## 2 Aroma Volatile Composition and Their Biological Characteristic of Major Fruits
### Volatile Compounds and Their Biological Characteristic of Major Fruits
Six major volatile compounds were identified (hexanal, (_E_)-2-hexenal, linalool, 1-hexanol, ethyl octanoate, and hexyl acetate) in apricot fruit cv. \"Modesto\", all of which were previously reported to be major contributors to apricot aroma [69; 70]. The most abundant volatile compounds in terms of concentration were aldehydes, mainly hexanal and (_E_)-2-hexenal, and their concentration decreased during ripening with significant differences. Terpenic compounds (i.e. linalool) and alcohols (i.e., 1-hexanol) were produced at a lower concentration than aldehydes, and decreased during ripening with a similar pattern to that observed for aldehydes [69]. Grape (_Vitis vinifera_ L.) volatiles include a great number of compounds, among which monoterenes, C\({}_{13}\) norisoprenoids, alcohols, esters and carbonyls are found [71]. Grape may be divided into aromatic and nonaromatic varieties. Free terpen, for example, linalool and geraniol, have been identified as major aroma compounds in both red and white grapes [72]. Octanoic acid and alcohols, particularly 2-phenylethylanol, are recognized after crushing [72]. In addition, esters and aldehydes were also reported in \"Aleatico\" grapes [73]. The most abundant free compounds detected in muscat grape were linalool, geraniol, citronellol, nerol, 3,7-dimethyl-1,5-ocatadien-3,7-diol (diendiol I) and 3,7-dimethyl-1,7-ocatadien-3,6-diol (diendiol II). In the glycosylidically-bound fraction the major compounds were geraniol, linalool, citral, nerol, citronellol, \(\alpha\)-terpineol, diendiol I, diendiol II, _trans_-furan linalool oxide (linaloxide I), _cis_-furan linalool oxide (linaloxide II), benzyl alcohol and 2-phenylethanol. Other monoterenes potentially contributing to Muscat aroma were rose oxide, citral, geraniol, nerol and citronellol [74]. (_E_)-2-hexenal was the most abundant volatile compound in Riesling and Cabernet Sauvignon grapes, and it showed a significant increase in concentration after veraison. Benzene derivatives discriminated ripe Cabernet Sauvignon grapes, whereas monoterenes and sesquiterpenes discriminated both cultivars pre-veraison with a broader range of terpen observed in the Cabernet Sauvignon samples compared with the Riesling samples. At veraison, terpene production in both varieties was low, but Riesling grapes produced some terpen (geraniol and \(\alpha\)-murolene) post-veraison. Generally, esters and aldehydes were the major class of compounds from Riesling grapes, while Cabernet Sauvignon showed a greater tendency to form alcohols [75]. Aroma compounds in raspberry (_Rubus idaeus_ x _ursimus_) have been studied extensively. At least 200 volatile compounds have been identified in this fruit. Many compounds including raspberry ketone, \(\alpha\)-ionone, \(\beta\)-ionone, linalool, (\(Z\))-3-hexenol, geraniol, nerol, \(\alpha\)-terpineol, Furaneol, hexanal, \(\beta\)-ocimene, 1-octanol, \(\beta\)-pinene, \(\beta\)-damascenone, ethyl 2-methylpropanoate, (\(E\))-2-hexenal, heptanal, and benzaldehyde have been identified to contribute raspberry aroma. Among them, \(\alpha\)-ionone, \(\beta\)-ionone, geraniol, nerol, linalool, and raspberry ketone could be particularly important to red raspberry aroma [76]. Twenty-nine volatile compounds were quantified in \"Chilliwack\", \"Tulamenen\", \"Willamette\", \"Yellow Meeker\", and \"Meeker\" raspberries, data showed that volatile concentrations varied for different cultivars. Large variations for \(\alpha\)-ionone, \(\beta\)-ionone, geraniol, linalool, and (\(Z\))-3-hexenol were observed in different raspberry cultivars. In addition, the volatile compositions in \"Meeker\" raspberry grown at different locations also varied [77]. Although blackberry (_Rubus laciniata_) has been widely planted, the study of blackberry flavor is still very limited. The early studies focused on the volatile constituents of blackberry, and very diverse compounds have been identified.