Flavour chemistry of methylglyoxal and glyoxal
Methylglyoxal (MGO) and glyoxal (GO), known as reactive carbonyl species, can be generated endogenously and exogenously (human body and food system). They are attracting increased attention because of their relationship with diabetes and flavour generation. In this review, their characteristics relating to flavour chemistry are discussed. MGO and GO can be detected in food systems by GC and HPLC after derivatization. MGO and GO formed in the Maillard reaction play important roles as precursors of aroma and colour compounds, especially in Strecker degradation, a major flavour generation reaction. When combined with amino acids they undergo Schiff base formation, decarboxylation and α-aminoketone condensation leading to heterocyclic aroma compounds such as pyrazines, pyrroles and pyridines. They attack amine groups in amino acids, peptides and proteins to form advanced glycation end products (AGEs) and cause carbonyl stress followed by oxidative stress and tissue damage. Therefore, many studies about scavengers of MGO and GO are seen. The influence of these scavengers on flavour generation is also discussed.