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

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 isola te and characterize the different compounds that are produced in the a bove system in order to elucidate the mechanisms that take place at th e molecular level upon microwave irradiation. Six pyrrole derivatives were isolated and characterized by H-1 and C-13 nuclear magnetic reson ance spectroscopy and mass spectrometry. They were 1-[5'-amino-(1' and 5')-carboxypentyl]pyrrole (3 and 4, respectively), 1-[5'-amino-(1' an d 5')-carboxypentyl]-2-(1''-hydroxypropyl)pyrrole (5 and 6, respective ly), and 1-(5'-amino-1'-carboxypentyl)-2-[(Z and E)-1''-propenyl]pyrro le (7 and 8, respectively). Two of these compounds (7 and 8) were not previously found during thermic heating at low or moderate temperature s. A possible mechanism that explains the formation of all these compo unds is suggested and discussed in relation to the formation of color and fluorescence in this system.