# Aroma Volatiles in Litchi Fruit: A Mini-Review
## 3 Characteristics of VOCs in Litchi Fruit
### **Litchi cultivars**
\begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{**CAS**} & \multirow{2}{*}{\
\begin{tabular}{l} **Volatile Organic** \\ **Compounds** \\ \end{tabular} } & \multicolumn{2}{l}{
\begin{tabular}{l} **Number** \\ **of** \\ **Hits** \\ \end{tabular} } & \multicolumn{1}{l}{\multirow{2}{*}{**Scent Descriptions**}} & \multirow{2}{*}{**Substance Classifications**} \\ \cline{1-2} \cline{4-4}  & & & & \\ \hline
78-70-6 & Linalool & 21 &
\begin{tabular}{l} Floral scent of lilac, lily of the valley \\ and rose \\ \end{tabular} & Monoterpenses \\ \hline
106-24-1 & Geraniol & 20 &
\begin{tabular}{l} Rose-like aroma \\ \end{tabular} & Monoterpenses \\
138-86-3 & DL-Limonene & 18 & Orange and lemon-like aroma & Monoterpenses \\ \hline
586-62-9 & Terpinolene & 17 &
\begin{tabular}{l} Lemon, woody and slightly sweet \\ citrus-like aroma \\ \end{tabular} & Monoterpenses \\
111-27-3 & 1-Hexanol & 17 &
\begin{tabular}{l} fruitly-like aroma \\ \end{tabular} & Alcohols \\
106-22-9 & \(\beta\)-Citronellolol & 17 & Sweet rose-like aroma & Monoterpenses \\
99-87-6 & \(P\)-Cymene & 16 & Aromatic smell & Monoterpenses \\
106-25-2 & Nerol & 16 &
\begin{tabular}{l} Rose and orange-like aroma \\ \end{tabular} & Monoterpenses \\
60-12-8 & 2-Phenylethanol & 16 &
\begin{tabular}{l} Rose-like aroma \\ \end{tabular} & Primary alcohol benzes \\
98-55-5 & a-Terpinol & 15 &
\begin{tabular}{l} Clove aroma \\ \end{tabular} & Monoterpenses \\
111-87-5 & Octanol & 15 & Strong only and citrus aroma & Saturated fatty alcohol \\
876-17-5 & \(cis\)-Rose oxide & 15 &
\begin{tabular}{l} Rose-like aroma \\ \end{tabular} & Monoterpenses \\
104-76-7 & 2-Ethylehexanol & 15 & Special aroma & Primary alcohol \\
123-35-3 & \(\beta\)-Myorene & 14 & Light balsamic aroma & Monoterpenses \\ \hline
3391-86-4 & 1-Octen-3-ol & 14 &
\begin{tabular}{l} Mushroom, lavender, rose, and hay aroma \\ \end{tabular} & Aliphatic unsaturated alcohol \\ \hline
562-74-3 & 4-Terpinol & 14 &
\begin{tabular}{l} Warm peppery, lighter earthy, and \\ aged wood aroma \\ \end{tabular} & Monoterpenses \\ \hline
5392-40-5 & Citral & 14 & Intense lemon scent & Monoterpenses \\
141-78-6 & Ethyl acetate & 14 & Fruity aroma & Esters \\
513-86-0 & Acetoin & 13 & Pleasant creamy aroma & Methyl ketone \\ \hline
556-82-1 & Premol & 13 & Fruity aroma & Alkenyl alcohol \\
106-26-3 & Neral (_cis_-Citral) & 13 & Lemon-like aroma & Monoterpenses \\ \hline \hline \end{tabular}
\end{table} 
Table 2: List of 21 VOCs commonly found in litchi fruit and their aroma description. the main source of the flower scent, and the terpenoid production in litchi flowers was closely associated with the expression level of TPS gene family members [51; 52; 53]. Whether the activity of TPS has an impact on aroma formation in litchi fruit needs further studies. Alcohols could be derived from multiple biosynthesis pathways, including the oxidation lipoxygenase pathway, terpenoid pathway, methyl-branched pathway, and phenylalanine pathway [54]. As shown in Table 2, 1-hexanol, 2-phenylethanol, octanol, 2-ethylhexanol, 1-octen-3-ol, and phenol were the most common alcohols (occupying 28.6%) in litchi fruit. Among them, 1-hexanol, octanol, and phenol might produce a citrus scent, and 2-phenylethanol and 1-octen-3-ol might provide a rose scent [55; 56; 57]. In addition, 2-phenylethanol was reported to be the key VOC in the NMC, \"Mauritius\", \"Brewster\", and \"Hak Ip\" cultivars [32; 39], and 1-octen-3-ol was the important VOC in FZX, GYL, ZF, XL, and JZL [24; 35]. These findings suggest that the aroma characteristics of alcohols might play an important role in regulating aroma formation in litchi fruit.