Browning of Maillard reaction systems containing xylose and 4-hydroxy-5-methyl-3(2H)-furanone.

Pentose is involved in the browning through the Maillard reaction of food derived of plant origin. During research on the Maillard reaction between xylose (Xyl) and lysine (Lys), we detected 4-hydroxy-5-methyl-3(2H)-furanone (HMFO) as a major decomposition product of Xyl. To clarify the chemical pathway of the browning of pentose system, the formation and decomposition of dicarbonyls from HMFO and Xyl were examined. In the HMFO system, HMFO was oxidatively hydrolyzed to form 2-hydroxy-3,4-dioxopentanal, which leads to the formation of methylglyoxal (MGO) and then diacetyl (DA). In the Xyl system, MGO was also the major dicarbonyl degradation product from 1-deoxyxylosone (1-DX). Among Xyl, HMFO, MGO, and DA, MGO turned brown most rapidly in the presence of Lys and formed melanoidin-like brown pigments. In the Xyl system, MGO derived from HMFO and 1-DX most contributed to the browning, although some low-molecular-weight pigments, a colorless polymer, and fluorescent substances were also formed.