Effect of the C-Ring Structure of Flavonoids on the Yield of Adducts Formed by the Linkage of the Active Site at the A-Ring and Amadori Rearrangement Products during the Maillard Intermediate Preparation

Flavonoids (dihydromyricetin, dihydroquercetin, epicatechin, and epigallocatechin) were applied to indicate the critical formation condition of the Amadori rearrangement product (ARP) in Maillard reaction performed under a two-step temperature rising process in the threonine-xylose model system. Threonine-ARP (Thr-ARP) was mixed with dihydromyricetin (DM), dihydroquercetin (DQ), epicatechin (EC), and epigallocatechin (EGC) before the heat treatment; then, the mixture was tested by liquid chromatography-mass spectrometry (LC-MS). The results showed that these flavonoids trapped the ARP and generated adducts. The A-ring of flavonoids (the meta-polyhydroxylated benzene ring) was the functional group to capture the Thr-ARP. The relative contents of the adducts of DM-Thr-ARP, DQ-Thr-ARP, EC-Thr-ARP, and EGC-Thr-ARP were compared with each other, and it was found that the structure of the C-ring of the flavonoids (the carbonyl group on C-4) significantly impeded the formation of adducts with Thr-ARP, while the number of hydroxyl groups on the B-ring had little influence. The formation of adducts delayed the degradation of Thr-ARP, decreased the production of α-dicarbonyl compounds, and suppressed Maillard browning. In this way, the flavonoids might trace the critical formation conditions of ARP during the two-step temperature rising process.