## 3 Results and Discussion
### Chemical Patterns Characterizing Hazelnut Phenotype  
The goal of the first pattern recognition was to evaluate the role of cultivar and pedoclimatic conditions on the metabolome expression (phenotype). In a previous study on primary metabolites signatures of high-quality hazelnuts [37], it was found that, based on this fraction, analyzed samples were independently clustered according to cultivar/origin. In particular, Piedmont (Tonda Gentile Trilobata) and Roman (Tonda Romana) hazelnuts were connoted by the greater relative abundance of several amino acids and sugars, delineating distinctive yet discriminant signatures. On the other hand, Turkish hazelnuts, from the Ordu region, were connoted by a generalized lesser amount of primary metabolites with the exception of Gly and tartaric acid. Moreover, the discrimination between Piedmont \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Chemical Class** & **Compound Name** & \({}^{\mathbf{1}}\mathbf{t}\mathbf{R}\) **(min)** & \({}^{\mathbf{2}}\mathbf{t}\mathbf{R}\) **(sec)** & **Experimental \(\mathbf{I}^{\mathbf{T}}\)** & **Reference \(\mathbf{I}^{\mathbf{T}}\)** \\ \hline \multirow{9}{*}{Sugars} & 2-Deoxyribose 3 TMS & 33.2 & 0.9 & 1397 & 1404 \\  & Erythrose 3 TMS & 34.6 & 0.8 & 1426 & 1431 \\  & Deoxyribopyranose 3 TMS & 38.4 & 0.7 & 1504 & 1502 \\  & Ribofuranose 4 TMS & 43.0 & 0.8 & 1610 & 1625 \\  & anti-Fructose 5 TMSa & 53.0 & 0.8 & 1866 & 1867 \\  & syn-Fructose 5 TMSa & 53.4 & 0.8 & 1876 & 1878 \\  & Galactose 5 TMS & 53.7 & 0.8 & 1889 & 1896 \\  & Glucose 5 TMSa & 53.9 & 0.8 & 1891 & 1897 \\  & Mannitol 6 TMSa & 55.3 & 0.7 & 1932 & 1928 \\  & Trehalose TMS & 66.8 & 1.1 & 2302 & 2304 \\  & Sucrose 5 TMSa & 75.4 & 1.0 & 2627 & 2623 \\  & 2-\(\alpha\)-Mannobiose 8 TMS & 77.0 & 1.0 & 2693 & 2700 \\  & 3-\(\alpha\)-Mannobiose 8 TMS & 77.5 & 1.0 & 2715 & 2722 \\  & Galactino1 5 TMS & 81.3 & 0.9 & 2924 & 2926 \\  & Maltose 8 TMSa & 84.0 & 1.1 & 3062 & 2748 \\  & \(\beta\)-Lactose 8 TMS & 88.7 & 2.1 & 3269 & 3260 \\ \hline \multirow{9}{*}{Sugar acids} & \(\alpha\)-Hydroxylutaric acid 3 TMS & 41.4 & 0.9 & 1569 & 1576 \\  & \(\beta\)-Hydroxy-\(\beta\)-methylglutaric acid 3 TMS & 42.4 & 0.8 & 1596 & 1606 \\  & Galactaric acid 6 TMSa & 58.8 & 0.8 & 2037 & 2050 \\  & Galacturonic acid 5 TMSa & 68.4 & 1.0 & 2363 & 2370 \\ \hline \multirow{9}{*}{Others} & 3-Pyridinol TMS & 15.1 & 0.8 & 1032 & 1034 \\  & Diacetone alcohol TMS & 15.3 & 0.7 & 1036 & 1040 \\  & Hydroxylamine 2 TMS & 15.5 & 0.5 & 1042 & 1044 \\  & Hydroxylamine 3 TMS & 18.7 & 0.6 & 1114 & 1111 \\  & 2-Methyl-1,3-butanediol 2 TMS & 21.7 & 0.6 & 1175 & 1174 \\  & Diethylene glycol 2 TMS & 24.9 & 0.8 & 1237 & 1233 \\  & N-Butylacetamide 3 TMS & 48.9 & 0.9 & 1753 & 1755 \\  & Trypanime 2 TMS & 49.3 & 1.1 & 1764 & 1770 \\  & Glucono-1,4-lactone 4 TMS & 56.7 & 0.8 & 1972 & 1980 \\  & Pentaethylene glycol 2 TMS & 61.6 & 1.4 & 2127 & 2107 \\  & Bis-2-ethylhexyl phthalate & 69.1 & 1.4 & 2387 & 2381 \\  & Bis-(2-ethylhexyl) decanedioate & 79.2 & 1.4 & 2796 & 2792 \\  & Catechin 5 TMS & 80.5 & 1.1 & 2871 & 2861 \\  & \(\beta\)-Sitostol TMS & 88.2 & 2.1 & 3246 & 3249 \\ \hline \hline \end{tabular} Superscript letters following chemical names indicate previous studies where these compounds were described in relation to the roasting process: a indicates [PERSON] et al. [37], b [PERSON] et al. [9], and c [PERSON] et al. [10].  
\end{table} 
Table 2: _Cont._and Roman was mainly driven by glucose, galactose, maltose, and fructose, all present in higher amount in Tonda Gentile Trilobata as well as by Trp, Orn, and Tyr. In contrast, Tonda Romana hazelnuts were richer in Leu, Ile, Met, Val, Phe, Pro, and pyroglutamic acid and organic acids (lactic acid, glutararic acid, galacturonic acid, fumaric acid, tartaric acid, and oxalic acid).