CHARACTERIZATION OF THE PRODUCTS FORMED DURING MICROWAVE IRRADIATION OF THE NONENZYMATIC BROWNING LYSINE (E)-4,5-EPOXY-(E)-2-HEPTENAL MODEL SYSTEM

Previous studies have shown that a lysine/(E)-4,5-epoxy-(E)-2-heptenal model system may help to elucidate the nonenzymatic browning produced in foods by lipid peroxidation products during microwave heating. As a continuation of those studies, this research was undertaken to isolate and characterize the different compounds that are produced in the above system in order to elucidate the mechanisms that take place at the molecular level upon microwave irradiation. Six pyrrole derivatives were isolated and characterized by H-1 and C-13 nuclear magnetic resonance spectroscopy and mass spectrometry. They were 1-[5'-amino-(1' and 5')-carboxypentyl]pyrrole (3 and 4, respectively), 1-[5'-amino-(1' and 5')-carboxypentyl]-2-(1''-hydroxypropyl)pyrrole (5 and 6, respectively), and 1-(5'-amino-1'-carboxypentyl)-2-[(Z and E)-1''-propenyl]pyrrole (7 and 8, respectively). Two of these compounds (7 and 8) were not previously found during thermic heating at low or moderate temperatures. A possible mechanism that explains the formation of all these compounds is suggested and discussed in relation to the formation of color and fluorescence in this system.