Glycine, Diglycine, and Triglycine Exhibit Different Reactivities in the Formation and Degradation of Amadori Compounds

A series of Amadori compounds of glucose were prepared from glycine (G-ARP), diglycine (DiG-ARP), and triglycine (TriG-ARP), and identified by UPLC-MS/MS and NMR. The formation rate of ARPs was TriG-ARP > DiG-ARP > G-ARP, and their activation energies were 63.48 kJ/mol (TriG-ARP), 72.84 kJ/mol (DiG-ARP), and 84.76 kJ/mol (G-ARP), respectively, suggesting that ARP was formed more easily from small peptides than from amino acid. Although 1-DG was formed much more difficultly than 3-DG, the same order of the formation of 1-DG, 3-DG, and browning was DiGly > TriGly > Gly. It was also confirmed that more methylglyoxal and glyoxal would be formed from small peptides than equimolar amino acids. Compared with free amino acid, ARP, deoxyglycosones, and their secondary degradation products were more easily formed from dipeptide and tripeptide, thereby stronger browning occurred and higher reactivity was exhibited in Maillard reaction of di- or tripeptide.