Model Reactions on Roast Aroma Formation. 15. Investigations on the Formation of Pyridoimidazoles during the Maillard Reaction

Article abstract of DOI:10.1021/jf00056a048

When aqueous solutions of histidine and glucose were heated to 100, 120, 150, or 180 deg C or when this mixture was roasted at 220 deg C, a total of 231 volatile compounds were identified.Among them 2-acetyl- and 2-propionylpyrido<3,4-d>imidazole were found.Their formation pathway via a reaction of pyruvic aldehyde or 2-oxobutyraldehyde with, respectively, histidine or histimine is discussed.Experiments with 13C isotope labeled glucose point out that the terminal methyl groups of both aldehydes can arise from C-1 as well as C-6 of glucose.While pyruvic aldehyde can be formed by retro aldol scission of intermediate diacetylformoin, 2-oxobutyraldehyde was obviously formed from 2,5-dimethyl-4-hydroxy-3(2H)-furanone.By reaction of 1-, 2-, or 3-methylhistidine with glucose seven more pyrido<3,4-d>imidazoles were identified, the structures of which, like the structures of the above-mentioned compounds, were unknown up to now.Keywords: Roast aromas; Maillard reaction; pyrido<3,4-d>imidazoles; isotope labeling