## 3 Results and Discussion  
### Volatile Chemical Composition  
SPME-GC/MS analysis allowed to describe the volatile fraction from the headspace of fresh _C. australasia_ peel, pulp and seeds. In total, eighteen compounds have been identified and are listed in Table 1.  
In all three samples the monoterpene content exceeds the sesquiterpene one with limonene as the main compound reaching a percentage mean value of 62.6% in the peel, 41.5% in the pulp and 40.4% in the seeds. These data are in agreement with what was previously reported. In fact, limonene was found to be the main volatile constituent present in _C. australasia_ peels although with percentage values that may vary compared to the total volatile content [7; 16]. Relevant differences were detected between the investigated samples. From a qualitative point of view, the seeds were characterized by a fewer number of components detected. As known, VOCs compounds such as monoterpenes, sesquiterpenes and their oxygenated derivatives are primarily concentrated in the peel portion of the citrus fruit; in fact, essential oils are generally extracted from the peel. In contrast, the seeds are enriched in fixed oils sugars, tocopherols, phytosterols, carotenoids and minerals [17; 18; 19]. In the present work, \(\beta\)-pinene was detected only in the peel and with a significant relative \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \(\mathbf{N}^{\circ}\) & **COMPONENT 1** & **LRI 2** & **LRI 3** & **Peel 4 (\%)** & **Pulp 5 (\%)** & **Seeds 6 (\%)** \\ \hline
1 & \(\alpha\)-thujene & 918 & 923 & 0.4 \(\pm\) 0.02 & 0.4 \(\pm\) 0.03 & 0.6 \(\pm\) 0.03 \\
2 & \(\alpha\)-pinene & 935 & 943 & 1.5 \(\pm\) 0.02 & - & - \\
3 & sabienne & 958 & 962 & - & 0.8 \(\pm\) 0.03 & - \\
4 & \(\beta\)-pinene & 981 & 986 & 32.4 \(\pm\) 0.15 & - & - \\
5 & \(\alpha\)-phellandrene & 1000 & 1005 & - & 0.5 \(\pm\) 0.02 & - \\
6 & \(\alpha\)-terpinene & 1017 & 1019 & 0.2 \(\pm\) 0.02 & - & 4.8 \(\pm\) 0.05 \\
7 & limonene & 1024 & 1023 & 62.6 \(\pm\) 0.17 & 41.5 \(\pm\) 0.20 & 40.4 \(\pm\) 0.14 \\
8 & _cis-\(\beta\)_-cimene & 1035 & 1032 & 0.2 \(\pm\) 0.02 & 0.4 \(\pm\) 0.02 & - \\
9 & \(\gamma\)-terpinene & 1049 & 1054 & 0.7 \(\pm\) 0.03 & 14.8 \(\pm\) 0.09 & 13.9 \(\pm\) 0.07 \\
10 & isotropinolene & 1078 & 1081 & 0.1 \(\pm\) 0.00 & 2.0 \(\pm\) 0.02 & 1.3 \(\pm\) 0.02 \\
11 & _trans_-sabinene hydrate & 1091 & 1098 & 0.1 \(\pm\) 0.02 & 38.4 \(\pm\) 0.20 & 35.9 \(\pm\) 0.11 \\
12 & 1,3,8-\(p\)-menthatriene & 1115 & 1118 & - & 0.7 \(\pm\) 0.20 & - \\
13 & \(\delta\)-elemene & 1341 & 1347 & 0.6 \(\pm\) 0.06 & - & - \\
14 & \(\alpha\)-cubebeene & 1355 & 1350 & 0.1 \(\pm\) 0.00 & - & - \\
15 & \(\gamma\)-elemene & 1447 & 1445 & 1.0 \(\pm\) 0.03 & - & - \\
16 & \(\alpha\)-farnesene & 1489 & 1496 & - & 0.2 \(\pm\) 0.01 & - \\
17 & guaia-1(10),11-diene & 1501 & 1505 & - & 0.3 \(\pm\) 0.02 & 3.0 \(\pm\) 0.03 \\ \hline \multicolumn{2}{c}{SUM} & & 99.9 & 100.0 & 99.9 \\ \hline  & Monoterpene & & & 98.1 & 60.4 & 61.0 \\  & hydrocarbons & & & & & \\  & Oxygenated & & & & & \\  & monoterpenes & & & & & \\  & Sesquiterpene & & & & & \\  & hydrocarbons & & & & & \\  & Others & & & & & & \\ \hline \hline \end{tabular}  
* the components are reported according to their elution order on apolar column; 2 linear retention indices measured on apolar column; 3 linear retention indices from the literature; peel 4: percentage mean values of peel components (\%); pulp 5: percentage mean values of pulp components; seeds 6: percentage mean values of seeds components—not detected; tr: traces (mean value \(<\) 0.1%). The analyses were conducted in triplicate.  
\end{table} 
Table 1: Chemical composition (percentage mean value \(\pm\) standard deviation) of _C. australasia_ peel, pulp and seeds. concentration (32.4%). Other components such as, sabinene (0.8%), \(\alpha\)-phellandrene (0.5%), 1,3,8-\(p\)-menthatriene (0.8%) and \(\alpha\)-farnesene (0.2%), were present only in the pulp.