Indole: A Promising Scavenging Agent for Methylglyoxal and Related Carbonyls in Tryptophan Containing Maillard Model Systems.

In situ generation of efficient carbonyl trapping agents from amino acids during food processing can be considered a useful approach to control the accumulation of harmful Maillard reaction products in food. Tryptophan is one such amino acid that can be used to generate carbonyl trapping agents. Indole, the main thermal degradation product of tryptophan, is known to react with simple aldehydes through electrophilic aromatic substitution type reactions mainly at carbon positions 2 and 3 in addition to the ring nitrogen. The ability of indole to scavenge three moles of reactive aldehydes per mole of indole such as formaldehyde, methylglyoxal, and phenylacetaldehyde was investigated using model systems containing tryptophan or indole. The model systems were either (a) heated in an aqueous solution in stainless steel reactors at specified time and temperatures and analyzed by qTOF-MS/MS or (b) directly pyrolyzed and analyzed by GC/MS using isotope labeling technique. Unlike the other aldehydes, the initial alcohol formed with phenylacetaldehyde was able to dehydrate and form an stable conjugated system with the indole. In general, indole was able to capture three moles of paraformaldehyde, three moles of methylglyoxal and three moles of phenylacetaldehyde and suppress the formation of 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) generated in a model system.