Influence of α-dicarbonyl compounds to the molecular weight distribution of melanoidins in sucrose solutions:: part 1

The correlations between formation of melanoidins and the content of alpha-dicarbonyl compounds and colour formation were studied in Maillard reaction model sucrose solutions at high treating temperatures (130 degrees C) corresponding to the industrial sucrose processing. Molecular weight distribution was determined by gel permeation chromatography (GPC) and alpha-dicarbonyls as high reactive intermediates of the Maillard reaction were detected by RP-HPLC and GC/MS. Referring to formation of melanoidins, new knowledge could be gained. The investigations clearly point out, that individual alpha-dicarbonyls are involved in formation of specific molecular weight fractions. 3-Deoxyhexosulose (3-DH) and methylglyoxal are the important alpha-dicarbonyl compounds in thermal-treated sucrose solutions. A low molecular weight fraction with a molecular weight range of < 5,800 g/mol preferably occurs when 3-DH is formed in high concentrations. The high increase in intensity of a low molecular weight fraction is combined with a strong colour formation. In contrast to 3-DH, methylglyoxal promotes the formation of high molecular weight fractions between 6,600 g/mol and approximately 17,000 g/mol. Furthermore, model solutions with a high intensity of high molecular weight fractions show an early colour formation during the starting period of the reaction. Indeed, this early browning is not as intensive as the colour formation caused by the low molecular weight fraction during the later stage of the browning reaction. Out of this, 3-DH can be regarded as the most important intermediate for an intensive colour formation in sucrose solutions.