Non‐Enzymatic Browning Reactions of Phospholipids

Abstract

B y R J H i d a l g o , R . Z a m o r a , M . A l a i z , M . P . M a z a , R M i l l a n andE. V i o q u e "The formation and properties of the fluorescent compounds originated in the browning reactions of phospholipids have been investigated. The compounds exhibited fluorescence with excitation maximum 345-350 nm and emission maximum at 420630 nm, which were similar to those of lipofuscin and fluorescent substances derived from the reaction of oxidized fatty acids with glutathione. The fluorescence of the compound was affected neither with the pH 2-11 nor by treatment with sodium borohydride. The fluorescent compounds formed in the browning reaction of peroxidized phosphatidylethanolamine are produced, mainly, by interaction of the amine group of phosphatidylethanolamine and saturated aldehydes produced through the decomposition of fatty acid hydroperoxides of phosphatidylethanolamine. Phospholipids do not interact per se with bovine serum albumin, and their interaction is similar to that of polyunsaturated fatty acid hydroperoxides: the phospholipids give secondary products (aldehydes) that subsequently react with protein.

Changes Produced in the Antioxidative Activity of Phospholipids as a Consequence of Their Oxidation

“…Phospholipid Oxidation. The peroxidation of the phospholipids was achieved as described previously (11). Briefly, the phospholipid solution was evaporated to dryness under vacuum so that the phospholipid formed a thin layer on the inside surface of a round-bottom flask, which was then incubated under air in the dark at 60 °C.…”

“…In an attempt to clarify the consequences of oxidative processes in phospholipids, the present study determines the antioxidative activities of the three major phospholipids of soybean lecithin when added to soybean oil in both their native forms and after oxidation. In addition, the nonenzymatic browning of phospholipids with oxidation was also studied because of the well-known contribution of phospholipids to nonenzymatic food browning ( , ) and the formation in these reactions of heterocyclic residues () with antioxidant properties ( , ).…”

Browning and fluorescence development during microwave irradiation of a lysine/(E)-4,5-epoxy-(E)-2-heptenal model system

“…Nonenzymatic browning reactions are one of the major chemical reactions occurring in foods (Karel, 1984), and although it has been commonly associated with the interaction between reducing sugars and proteins (Maillard reaction), the interaction between oxidized lipids and proteins has been suggested to play a role into the above process (Eriksson, 1987;Hidalgo et al, 1990). The results obtained in this study show a great similarity between color and fluorescence developed after 100 s of microwave irradiation in both epoxyaldehyde/lysine and glucose/ lysine systems and, therefore, suggest a contribution of oxidized lipid/amino acid reactions to the final color and fluorescence developed in foods during microwave heating.…”