Nonenymatic Browning, Fluorescence Development, and Formation of Pyrrole Derivatives in Phosphatidylethanolamine/ Ribose/Lysine Model Systems

Abstract

ABSTRACTBrowning, fluorescence, and pyrrole formation were determined in 4 mixtures of phosphatidylethanolamine (PE), ribose (RI), and/or lysine (lys) incubated at 60°C to study the contribution of lipid oxidation to food browning when lipid oxidation products are formed in the presence of other food components. The 4 assayed systems (PE/lys, PE/RI, RI/lys, and PE/RI/lys) were also extracted with chloroform‐methanol (2:1) to distinguish between the nonenzymatic browning produced with the amino group of PE and that produced with the amino groups of lys. Under the assay conditions, both the RI and the oxidized products produced in the fatty acid chains of PE contributed to the development of browning in the assayed systems. However, RI and oxidation products of PE exhibited different reactivities for the different amino groups involved in these reactions. Thus, the oxidized lipids reacted with the amino group of PE with preference for the amino group of lys, and this preference was reversed for RI. These results suggest that the contribution of both carbohydrates and lipid oxidation products to food browning may be distinguished. In addition, determination of oxidized lipid/ethanolamine derivatives in phospholipids may be an alternative procedure to evaluate oxidative damage in foods.