NONENZYMATIC BROWNING AND FLUORESCENCE DEVELOPMENT IN A (E)-4,5-EPOXY-(E)-2-HEPTENAL LYSINE MODEL SYSTEM

As a model system for studying oxidized lipid/protein browning, the reaction between (E)4,5-epoxy-(E)-2-heptenal (a secondary oxidation product of omega-3 pentaenoic acids) and lysine was studied. CIELAB L*a*b* and fluorescence followed zero-order kinetics, and were always correlated, as a function of time, pH, temperature and epoxyaldehyde/lysine ratio, suggesting parallel reactions for producing brown macromolecular pigments and fluorescent products. Activation energy, according to the Arrhenius equation, was 66.5 and 50KJ/mol for color difference and fluorescence intensity, respectively. This model system may help understand the non-enzymatic browning produced by lipids.