Unraveling the formation mechanism of pyrazines and their derivatives in the glucose-glycine Maillard reaction using carbon module labeling coupled with carbonyl analysis

Previous and present studies confirm that glucose and glycine serve as key precursors for pyrazines contributing to the roasty aroma, but their formation pathways remain unclear. The formation pathways of pyrazines and their derivatives were elucidated by combining CAMOLA with carbonyls profiling. Continuous accumulation of early-stage Maillard products and melanoidins occurred during the glucose-glycine reaction at 160 °C, with 5-methyl-2-furanmethanol, hexanoic acid, and hexanoic acid pentyl ester identified as reliable reaction markers. Eight pyrazines were identified as temperature- and time-dependent products, which were dominated by unlabeled isotopologues from the recombination of glucose fragments. Products of aldol reaction and keto-enol tautomerism of 1-hydroxy-2-butanone and 1,3-dihydroxypropanone, together with glyoxal and methylglyoxal, reacted with glycine to produce aminocarbonyl intermediates. Differences in the structure and binding sites of aminocarbonyl intermediates were responsible for the formation of diverse pyrazines and their derivatives. This work provides a theoretical foundation for the targeted regulation of roasty aroma.