## 1 Introduction
### Grape and Wine Volatile Compounds
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Carbonyl compounds** & **Esters** & **Norisopenroids** \\ acetaldehyde & ethyl 2-methylpropanoate & TDN (1,1,6-trimethyl-1,2-dihydronaphthalene) \\ isobutyraldehyde & ethyl 2-methylbutanoate & \(\beta\)-damascone \\
2-methylbutanal & ethyl 3-methylbutanoate & \(\beta\)-damascenone \\ isovaleraldehyde & ethyl 2-hydroxypropanoate & vomifoliol \\
1-octen-3-one & ethyl 3-hydroxybutanoate & dihydroxycomifoliol \\ (_E_)-2-heptenal & ethyl 4-hydroxybutanoate & 3-hydroxy-\(\beta\)-damascone \\ methional & diethyl succinate & 3-oxo-\(\alpha\)-ionol \\ (_E_)-2-octenal & diethyl malate & 3-hydroxy-7,8-dihydro-\(\beta\)-ionol \\ hexanal & ethyl butanoate & \(\alpha\)-ionol \\ (_E_)-2-hexenal & ethyl hexanoate & \(\beta\)-ionol \\ (_Z_)-3-hexenal & ethyl octanoate & \(\alpha\)-ionone \\ (_Z_)-2-nonenal & ethyl decanoate & \(\beta\)-ionone \\ furfural & ethyl benzoate & actinidols \\
5-methylfurfural & isoamyl octanoate & vitispiranes \\
1H-pyrrole-2-carboxyaldehyde & ethyl furoate & Riesling acetal \\ gerani & ethyl dihydrocinnamate & hydroxy-megastigmen-2-one \\ neral & ethyl cinnamate & hydroxy-megastigmen-3-one \\ acetoin & methyl vanillate & 4-oxo-isoophorone \\ diacetyl & ethyl vanillate & \(\beta\)-isophorone \\ glyoxal & ethyl acetate & 4-oxo-2,3-dehydro-\(\beta\)-ionol \\ methylglyoxal & isobutyl acetate & \(\beta\)-cyclocitral \\ glycolaldehyde & isoamyl acetate & \\ hydroxypropandial & ethyl 2-phenylacetate & \\
2,4-nonadienal & hexyl acetate & \\
2,6-nonadienal & & \\ \hline
**Lactones** & **Nitrogen compounds** \\ \(\gamma\)-butyrolactone & 3-isobutyl-2-methoxypyrazine \\ \(\gamma\)-hexalactone & 3-sec-butyl-2-methoxypyrazine \\ \(\gamma\)-nonalactone & 3-isopropyl-2-methoxypyrazine \\ \(\gamma\)-decalactone & 3-ethyl-2-methoxypyrazine \\ _cis/trans_ oak lactone & \\ sotolon & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._Figure 1: Principal monoterepenes identified in grapes. In brackets, the odor descriptor is reported [24]. Figure 2: Principal C\({}_{13}\)-norisoprenoids identified in grapes. In brackets, the odor descriptor is reported [24]. Main wine volatiles are ethyl esters, acetates, and higher alcohols. Esters are produced by the yeasts during fermentation. Principal are ethyl esters characterized by fruity and floral notes, such as ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl dodecanoate, isoamyl acetate, hexyl acetate, and 2-phenylethylly acetate [32,33]. Contents of hexanoic, octanoic, and decanoic acid in wine depend on the yeast strain, fermentation conditions and grape must composition [27]. Higher alcohols are formed by the yeast sugar metabolism (anabolic pathway) as well as _via_ the catabolic or Ehrlich pathway of amino acids [27,34,35]. [PERSON] and [PERSON] reported that a higher alcohols concentration below 300 mg/L is desirable for the aroma complexity of wine whereas a concentration exceeding 400 mg/L can have a detrimental effect [36]. Volatile phenols, such as 4-vinylphenol (aroma descriptors: spicy, pharmaceutical), 4-vinylguaiacol (smoke, phenolic), 4-ethylphenol (horse stable, medicinal), and 4-ethyl guaiacol (spice, phenolic), are produced during alcoholic fermentation by some microorganisms (_Brettanonyces_ yeasts and bacteria) by decarboxylation of hydroxycinnamic acids present in must [32,33,37].