Bestimmung von Methylglyoxal in Karamel-Proben

Concentrated solutions of fructose (0.1 – 1 molfraction) in water were heated at 130 – 150 °C until 5 – 80 min in sealed test-tubes and the formed methyl-glyoxal was determined. Methyl-glyoxal reacts with o-phenylen-diamin, produces 3-methyl-chinoxalin absorbing in the UV range and gives a possibility to determine the methyl-glyoxal by HPLC. The first results show very few methyl-glyoxal since biggest part of them takes part in further reactions, too. If o-phenylen-diamin was given to the fructose solution before the heating process the methyl-glyoxal can react with it in the moment of formation. The methyl-chinoxalin was determined by HPLC and the methyl-glyoxal quantity was calculated. The formation of methyl-glyoxal from fructose takes place in a reaction of 1.5 order with an activation energy of 0.5 kJ/mol.