Mechanisms of Browning Degradation of d-Fructose in Special Comparison with d-Glucose-Glycine Reaction

Degradation mechanisms of d-fructose by the interaction with amino acids or organic acids in aqueous solution at initial pH 5.5 heated at 100°C were investigated and a substantial difference in mechanisms between fructose degradation and glucose-glycine reaction was presented. d-Fructose browned more intensely than did d-glucose in lower concentration of glycine and/or in earier stage of reaction period. By catalytic action of carboxylate anions without any condensation with amino groups, d-fructose was decomposed to 3-deoxy-d-erythrohexosulose, 5-(hydroxymelhyl)-2-furaldehyde, and a less amount of pyruval-dehyde through caramelization. It was considered that the main path of fructose degradation was 1,2-enolization but 2,3-enolization would also occur to a little extent.