2 Different approaches to produce the same molecule
Pyrazines are formed by the condensation of two molecules of α-aminocarbonyls such as amino acids or amino sugars (Maillard reaction) [18]. The two aminocarbonyl compounds firstly react to form a dihydropyrazine and subsequently undergo aromatization by oxidation with air or elimination of a hydroxyl group to form the side chain. Pyrazines can be extracted and distilled in low amounts directly from natural sources such as vegetables, coffee, cocoa and nuts, most of them deliberately formed at elevated temperature in roasting processes in the case of coffee and cocoa [17, 19] (Figure 3, C ) or unintentionally in refining processes of e.g. white sugar [20].