Role of exogenous xylose during its co-heating with alanine-xylose Amadori compound: Competitively promoting 2-furfural formation and limiting pyrazines generation

Exogenous xylose (Xyl) could promote 2-furfural formation but inhibit pyrazines generation during its co-heating with alanine (Ala)-Xyl Amadori rearrangement product (AX-ARP). The activation energy of AX-ARP formation from Ala and Xyl was considerably lower than that of pyrazine formation from Ala and glyoxal (GO). Accordingly, the preferential interaction of exogenous Xyl with regenerated Ala triggered a continuous cycle of consumption and regeneration of Ala in AX-ARP-Xyl model. In this way, functioning as a catalyst, regenerated Ala facilitated the continuous conversion of AX-ARP into deoxyxylosones (DXs). However, exogenous Xyl accelerated the pH drop during the thermal treatment of AX-ARP, which favored the conversion of DXs into 2-furfural while limiting the transformation of their α-dicarbonyl fragments into pyrazines. Model reactions of AX-ARP-[ 13 C 5 -Xyl] further confirmed that exogenous Xyl was progressively converted into 2-furfural, while its downstream products, such as GO and methylglyoxal (MGO), did not exhibit an enhanced tendency to form pyrazines.