LC/MS analysis and antioxidative efficiency of Maillard reaction products from a lactose-lysine model system

Aqueous solutions of lactose and lysine were refluxed for up to 4 h without pH control. Samples were collected every hour, and the reaction was monito red by measuring the pH, the optical density at 420 nm, and the relative an tioxidative efficiency (RAE). The greatest change in optical density and an tioxidative efficiency occurred for the mixture heated for 4 h. The 4 h sol ution was separated into three fractions according to the molecular weights of the components and tested for RAE. The high molecular weight fraction w as more colored, and it had the highest antioxidative activity. The low mol ecular weight fraction was separated by high-performance liquid chromatogra phy (HPLC). RAE values were measured for each purified compound. HPLC coupl ed with diode array and electrospray mass spectrometry allowed a rapid scre ening of the solutions and a tentative identification of several peaks. Nuc lear magnetic resonance analysis allowed the identification of galactosylis omaltol and pyrraline. The resonance assignments for these compounds were r evised.