Formation of discrete molecular size domains of melanoidins depending on the involvement of several α-dicarbonyl compounds:: Part 2

The correlation of several alpha-dicarbonyl compounds with the melanoidin formation and their molecular size distribution was investigated. The results point out that alpha-dicarbonyl compounds, which were formed during the Maillard reaction, are not only the most important intermediates but also the direct precursors for carbohydrate-based melanoidins. Discrete molecular size domains are detected by size exclusion chromatography (SEC-DAD/ RI), which were formed depending on the involvement of several alpha-dicarbonyls by thermal treatment of sucrose Maillard reaction solutions. By investigating sucrose Maillard reaction solutions spiked with methylglyoxal and 3-deoxyhexosulose carried on with direct melanoidin formation in aqueous solutions with alpha-dicarbonyls, molecular size domains of melanoidins could be connected for the first time with the reaction of several involved alpha-dicarbonyl compounds. High molecular size domains formed on the basis of methylglyoxal, whereas 3-deoxyhexosulose and D-glucosone promote lower molecular size domains. Concerning colour measurement methylglyoxal shows the highest browning activity followed by 3-deoxyhexosulose and D-glucosone. The reactivity of alpha-dicarbonyls and a correlated colour formation increase with rising alkaline pH-value. At a pH 5 the degradation and colour formation of alpha-dicarbonyl compounds is suppressed. The results provide new knowledge about colour formation in sucrose solutions.