## Results and Discussion  
### Comparing VOCs in Kernels and Craft Beers  
A total of 149 and 31 VOCs were identified in wheat kernels and wheat craft beers, respectively (data not shown). Since the aim of this research work was to find relationships and differences between raw materials and their respective processed food on the basis of aroma profile, a description focused on the individual dataset was avoided. However, a complete list of the molecules (listed in Table S1), their putative origin, and biosynthesis were described in the previous paper independently for wheat kernels [5; 10; 11] and wheat craft beers [16]. The datasets obtained from the two matrices were somewhat different, both in terms of numbers and chemical compounds, confirming the radical impact of this type of food process on the aroma profile of raw materials. Wheat kernels revealed a volatile profile considerably more complex but relative less intense considering the absolute area under the curve in the chromatograms. On the contrary, the wheat craft beers presented a limited number of compounds, but with higher peak area mostly due to ethyl ester compounds generally found at elevated concentrations in beer [18; 19]. The most numerous chemical group in wheat kernel was terpenes, which became the least represented VOC in wheat beer, with only \(\beta\)-Linalool identified, a hop-marker compound deriving partially from the oxidation of \(\beta\)-Myrce during the boiling process [20]. However, it has been demonstrated that during boiling and fermentation, due to oxidation and enzymatic phenomena, the majority of hop-derived volatiles, especially terpenes, are transformed or even lost [21; 22]. It is reasonable to assume that the same process could affect the terpenes deriving from other raw ingredients such as ground wheat. Concerning wheat beer, the most important chemical group is represented by esters. These compounds are known to derive from yeast metabolism by the enzymatic chemical condensation of fatty acids with ethanol or with higher alcohols (also known as fused alcohols), which in turn are synthesized along the Ehrlich pathway through transamination, decarboxylation, and the reduction of amino acids [23]. Thus, wheat kernel may influence the final esters composition of beers both because it contains already higher alcohols such as 2-Methyl propanol, 2-Methyl butanol, 3-Methyl butanol, and Phenethyl alcohol and also because it affects the nutritional composition of the word from which yeasts obtain nutrients. In order to enhance as much as possible the contribution of wheat volatiles to the beer flavor profile, the craft beers were made with reduced concentrations of hops and yeast and with the maximum level (40%) of wheat allowed by Italian legislation (Legge n. 1354/1962, art.1, c. 4). This technological approach permitted obtaining wheat beers having 14 VOCs in common with wheat kernels (Table 1) of which were: five alcohols, three organic acids, two aldehydes, and two esters. In order to better visualize and describe this dataset, a PCA was computed. In particular, Figure 1 shows the results of a PCA highlighting a clear separation between kernels and beers on the basis of common volatiles along the first component (accounting for the 69.9% of the total variance). Wheat kernels were characterized by Decanoic acid (fatty odor), Pentanoic acid (cheesy odor), 2-Nonanone (fruity odor), 1-Hexanol-2-ethyl (citrus odor), 1-Octanol (waxy odor), Nonanal (aldehydic odor), Decanal (aldehydic odor), 1-Decanol (fatty odor), and Ethyl dodecanoate (waxy odor), whereas Styrene (balsamic odor), Phenylethyl alcohol (sweet odor), 1-Butanol-2-methyl (roasted odor), Octanoic acid (fatty odor), and Ethyl decanoate (waxy odor) characterized wheat beers. Wheat kernels were distinguished by mainly oxidative compounds (alcohols and aldehydes) that in beers were found in a relatively lower amount.