Exogenous xylose trapped threonine to regenerate Amadori compounds and accelerated pH decline impeding pyrazines formation upon thermal treatment of Amadori compounds revealed by Isotope labeling

The isotope labeling method was adopted to reveal the mechanism by which exogenous xylose inhibited pyrazine compounds generation during thermal processing of Thr-ARP in this study. The [ 13 C 5 ]-D-xylose/Thr-ARP model reaction system was heated, the reaction products under 120°C and an initial pH 7.5 were tracked and determined by UPLC-MS, the ion fragmentation mechanism indicated [ 13 C 5 ]-Thr-ARP was formed. It was proposed [ 13 C 5 ]-D-xylose trapped threonine regenerated from Thr-ARP and then underwent Amadori rearrangement to form [ 13 C 5 ]-Thr-ARP. Thr-ARP's regeneration delayed the release of regenerated threonine and partially hindered Strecker degradation to generate pyrazine compounds. In addition, the self-cleavage of exogenous xylose caused an increase in the concentrations of 1-deoxyxylosone and 3-deoxyxylosone. The organic acids generated from the cleavage of deoxyxylosones led to an accelerated decrease in pH, reducing regenerated threonine’s nucleophilicity. The synergistic effect of the above two factors led to a reduction in the concentration and variety of pyrazine compounds produced by the thermal degradation of Thr-ARP. • Xylose inhibited pyrazines formation during Amadori compounds (ARP) degradation. • Isotope labeling revealed that [ 13 C 5 ]-xylose and threonine formed [ 13 C 5 ]-ARP. • Xylose accelerated rate pH decline rate during the ARP degradation. • ARP‘s reforming and pH accelerated decrease jointly inhibited pyrazines formation.