Identification of the Maillard reaction intermediates as divalent iron complexes in alanine/glucose/FeCl2 model system using ESI/qTOF/MS/MS and isotope labelling technique

Abstract

Due to their high reactivities and short half-lives, the detection of Maillard reaction intermediates is relatively difficult to achieve in a single analytical run. In this study, the formation of Maillard reaction intermediates from heated alanine/glucose mixtures (110 ​°C for 2 ​h) was investigated through their complexation with divalent iron using electrospray ionization/quadrupole time-of-flight mass spectrometry and isotope labeling techniques. Analysis of the mixtures indicated that this approach allows the simultaneous detection of many important labile and reactive Maillard reaction intermediates along with unreacted alanine and glucose in addition to various other Maillard reaction products, such as glyceraldehyde, erythrose, ribose, acetol, glycolaldehyde, fructosamine, glucosone, osones, deoxyosones, and Amadori products. Some osones and deoxyosones also formed their corresponding Schiff bases with alanine. The above mentioned Maillard reactions intermediates were detected either as binary metal complexes with alanine or with other enediol generating species including self-complexation adducts and they formed positively charged ions such as [M + H]+, [M + Na]+, [M + K]+, [M ​+ ​Fe35Cl]+, and [M ​+ ​Fe37Cl]+, that can be detected using the positive ionization mode.