Flavour precursor peptide from an enzymatic beef hydrolysate Maillard reaction-II: Mechanism of the synthesis of flavour compounds from a sulphur-containing peptide through a Maillard reaction

Abstract

This study aims to investigate the Maillard reaction products (MRPs) generated between enzymatic beef hydrolysated sulphur-containing oligopeptides and xylose subjected to heat treatment. The priority of the meat aroma contribution is Cys-Gly-Val > GSH > Leu-Cys, whereas Val-Met is relatively Maillard inert. Two peptide-specific aroma compounds, namely, 2-Isobutylpyrazine and 4-butyl-2,5-dimethylthiazole, were produced in a Leu-Cys Maillard reaction system at pH 5.5, showing that the dipeptides with Leu in the N-terminus exhibited high Maillard reactivity. The carbon source and generation pathway of the aroma-active compounds were demonstrated by carbohydrate module labelling (CAMOLA). A new pyrazine generation pathway with xylose-contributed C2 was proposed using this method specifically. Ultra-performance liquid chromatography-electrospray ionization/quadrupole-time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF MS/MS) was then used to analyse the peptide-specific MRPs to reveal the peptide cleavage, cyclization, and cross-linking with other reactants and intermediates. The main results of this study include that cross-linking between reactants and their intermediates largely occurred in a peptide-specific Maillard reaction; its oligopeptide-specific MRPs were first demonstrated; and the cross-linking products from cyclopeptides and two xyloses and/or their fragments were observed for the first time.