## 3 Results and Discussion
### Specie Variability between Tuber borchii and Tuber mesentericum
In particular, in decreasing order of quantity for _Tuber mesentericum_, there were volatile aromatic compounds, alcohols, aldehydes, volatile phenols, ketones, sulphur compounds, and volatile acids (Figure 2). In _T. borchii_, alcohols were the dominant VOCs, followed by aldehydes, ketones, sulphur compounds, and volatile acids. Alcohols have previously been identified as the most abundant compounds in _Tuber borchii_[26]. It is reported that the order of VOC levels of different truffles is from highest to lowest for black truffle, wh \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**Odour Descriptor**} & \multicolumn{2}{c}{**Peak Area (\%)**} \\ \cline{3-4}  & & _T. borchii_ & _T. mesentericum_ \\ \hline Aromatic compounds & & & \\
4-ethyl-5-methylthiazole & Nutty & 0.44 \(\pm\) 0.03 a & 0.01 \(\pm\) 0.00 b \\ pyrrole & Nutty & 0.03 \(\pm\) 0.01 a & 0.01 \(\pm\) 0.00 b \\
2-methylmercaptoethanol-benzothiazol & & 0.02 \(\pm\) 0.00 b & 0.14 \(\pm\) 0.03 a \\
3-methylanisole & Floral, spicy & 11.96 \(\pm\) 1.47 b & 66.63 \(\pm\) 2.38 a \\ p-ethylanisole & Naphthyl & 0.02 \(\pm\) 0.00 b & 0.54 \(\pm\) 0.04 a \\ benzaldehyde & Almond & 0.89 \(\pm\) 0.04 a & 0.16 \(\pm\) 0.03 b \\ phenylacetaldehyde & Green, floral & 0.60 \(\pm\) 0.03 a & 0.04 \(\pm\) 0.01 b \\
2,3-dimethoxyytoluene & & 0.18 \(\pm\) 0.00 a & 0.14 \(\pm\) 0.04 a \\
1,4-dimethoxy benzene & Nut-like & 1.32 \(\pm\) 0.10 a & 0.04 \(\pm\) 0.00 b \\
1,3-dimethoxy benzene & Coconut, hazelnut, earthy & 0.09 \(\pm\) 0.01 a & 0.04 \(\pm\) 0.01 b \\
2,5-dimethoxyytoluene & Floral & 0.05 \(\pm\) 0.01 b & 8.49 \(\pm\) 2.04 a \\
3,4-dimethoxyytoluene & & 0.01 \(\pm\) 0.00 b & 0.95 \(\pm\) 0.23 a \\
3,5-dimethoxyytoluene & & 0.15 \(\pm\) 0.03 b & 0.88 \(\pm\) 0.14 a \\ Z-2-phenyl-Z-2-butenal & Musty, cocoa & 0.08 \(\pm\) 0.01 a & 0.02 \(\pm\) 0.00 b \\
3,4,5-trimethoxytoluene & & 0.03 \(\pm\) 0.00 b & 0.05 \(\pm\) 0.01 a \\ \hline Volatile phenols & & & \\
4-methylguaiacol & Spicy, smoky & 0.03 \(\pm\) 0.01 a & 0.03 \(\pm\) 0.00 a \\ m-cresol & Phenolic, medicinal-leathery, smoky & n.d. & 2.13 \(\pm\) 0.21 \\
4-methoxy-3-methylphenol & Phenolic & 0.02 \(\pm\) 0.00 a & 0.02 \(\pm\) 0.00 a \\ \hline Volatile acids & & & \\ octanoic acid & Musty, pungent & 0.13 \(\pm\) 0.02 a & 0.03 \(\pm\) 0.00 b \\ nonanoic acid & Waxy & 0.17 \(\pm\) 0.09 a & 0.06 \(\pm\) 0.01 a \\ \hline \hline \end{tabular}  
* The values are reported as the mean followed by the standard deviation of three replicates. Values are indicated as peak area percentages (%). Different letters indicate statistically significant differences (\(p<\) 0.05). n.d.: not detected.  
\end{table} 
Table 2: _Cont._  
Figure 2: Relative quantities of chemical classes of volatile compounds quantified in the headspace of _Tuber borchii_ and _Tuber mesentericum_. truffle, respectively, with black truffle reportedly producing over 100 times more aromatic compounds than others [3], as we observed between the black and the bianchetto truffle. These qualitative and quantitative differences in terms of VOCs contributed to the classification and discrimination of _Tuber mesentericum_ and _Tuber borchii_ into two distinct groups, as highlighted by the cluster analysis visualised as a heatmap (Figure 3). Figure 3: Heatmap of significantly different (\(p<0.05\)) volatile compounds of _T. borchii_ and _T. mesentericum_ samples. Volatile compounds were plotted on the Y axis, while the X axis had the samples. Results are displayed as negative (\(-1\)) to positive (\(+1\)) correlation of the volatile compounds in the permuted matrix for the respective truffle samples. This subdivision is due to the diversity of VOCs present in the two truffle species. In fact, two main clusters of volatile compounds have been identified. One was mainly related to volatile phenols and volatile aromatic compounds, mostly present in _T. mesentericum_. A second cluster was mainly formed by aldehydes, ketones, and alcohols, more representative of _T. borchii_. In _T.