INFLUENCE OF IRRADIATION TIME, PH, AND LIPID/AMINO ACID RATIO OIL PYRROLE PRODUCTION DURING MICROWAVE HEATING OF A LYSINE/(E)-4,5-EPOXY-(E)-2-HEPTENAL MODEL SYSTEM

摘要

Several lysine/(E)-4,5-epoxy-(E)-2-heptenal reaction mixtures, at various pHs and lipid/amino acid ratios, were irradiated for 15, 50, and 100 s in a microwave oven and then fractionated by high-performance liquid chromatography to better understand the nonenzymatic browning in foods by lipid peroxidation products during microwave heating. Peak areas of the characterized fractions were measured using chromatograms obtained at 250 nm. The irradiation time significantly decreased the peak area of the starting epoxyenealdehyde 1 and increased the peak areas of the formed 1-alkylpyrroles (3, 4), : 1-alkyl-2-(1'-hydroxypropyl)pyrroles (5, 6), and 1-alkyl-2-(1'-propenyl)pyrrole (7). Compounds 3, 4, and 7 showed a certain dependence on irradiation time, pH, and lipid/amino acid ratio. On the contrary, the formation of compounds 5 and 6 did not show a clear dependence on such variables, suggesting that these compounds were intermediates and were involved in further reactions. These results, and previous studies on nonirradiated samples, suggest a role of 1-alkyl-2-(1'-hydroxypropyl)pyrroles in the development of color and fluorescence in this system, when subject to microwave irradiation.