## 2 Aroma Volatile Composition and Their Biological Characteristic of Major Fruits
### Volatile Compounds and Their Biological Characteristic of Major Fruits
In the non-aromatic varieties they occur as aldehydes and alcohols. Strawberry has one of the most complex fruit aromas, made up of approximately 350 volatile compounds [5, 46]. The furanones 2,5-dimethyl-4-hydroxy-3(2_H_)-furanone (furaneol) and its methyl derivative 2,5-dimethyl-4-methoxy-3(2_H_)-furanone (mesifurane) are considered the dominating aroma compounds [47]. They contribute to the typical caramel-like, sweet, floral and fruity aroma. Esters, which are the most important group of strawberry aroma compounds, cover 90% of the total number of volatiles in ripe strawberry fruit [47]. Among the major esters are methyl and ethyl butanoate, butyl acetate, methyl and ethyl hexanoate. Other key aroma compounds are linalool, \(\gamma\)-decalactone and 2,3-butanedione though some of these key compounds tend to be cultivar-specific [47, 48]. Finally, aldehydes and alcohols such as hexanal, _trans_-2-hexanal and _cis_-3-hexen-1-ol are important for the green, unripe notes in strawberry aroma. Their concentrations are also cultivar and ripeness dependent [47]. Although more than 250 volatile components have been identified in banana [49], the banana fruity top notes are from volatile esters, such as isoamyl acetate and isobutyl acetate [50]. The concentrations of acetates and butanoates increased during ripening of banana fruit [49]. In addition, isoamyl alcohol, isoamyl acetate, butyl acetate, and elemicine were detected by olfactometric analyses as characteristics of banana odor [51]. The main volatile compounds found in \"Cavendish\" banana were (_E_)-2-hexanal and acetoin, in \"Plantain\": (_E_)-2-hexanal and hexanal, and in \"Frayssinette\": 2,3-butanediol and two diastereomeric solerols. The most abundant aglycones were 3-methyl butanol, 3-methyl butanoic acid,solerol (two diastereomers) and acetovanillone. This compound, rarely identified in fruits, was detected for the first time in conjugated volatile compounds of fruits. The abundance of these two diastereomer in the extracts of \"Frayssinette\" seemed to be characteristic of this variety of banana [52]. Citrus volatiles have been extensively examined over the past several decades. Esters are important as they are responsible for the flavor characteristic [27].While the major esters are ethyl esters of C\({}_{3}\) to C\({}_{4}\) organic acids, linalool is by far the most important alcohol. However, ketones, carvone, diacetyl, and acetoin are off-flavors. Volatile compounds in citrus fruits accumulate in oil glands of flavedo and in the oil bodies of the juice sacs. Over 100 volatile compounds have been identified for the first time in the juice of four varieties of citrus (Powell Navel orange (_Citrus sinensis_ L.), Clemenules mandarine (_C. reticulate_ [PERSON]), Fortune mandarine (_C. reticulate_ [PERSON]) and Chandler pummelo (_C. maxima_ [PERSON])). The differences in the volatile profile in citrus juice are mainly quantitative, and only a few compounds are variety-specific. In Chandler the most characteristic volatiles were principally aliphatic aldehydes, sesquiterpenes such as nootkatone and monoterenes such as 2-carene. Powell Navel orange showed the highest levels of esters such as nonyl acetate and of monoterenes such as 3-carene. Clemenules showed the highest levels of ketones 3-pentanone and \(\beta\)-ionone and Fortune showed the highest levels of some acetate esters such as ethyl and propyl acetate, this latter almost Fortune-exclusive [53]. Moreover, a total of 58 volatile components were identified and quantified in Dortyl oeryli orange juice, terpen quantitatively and qualitatively represent the main group of the volatile fraction. d,l-limonene was the major terpene component, followed by valencene. After terpen, terpen were clearly the dominant constituents. Linalool, terpinen-4-ol and \(\alpha\)-terpineol were the most abundant among the terpenol compounds. In terms of aroma contribution to orange juice, 12 compounds were prominent based on the odour activity values (OAVs).