Pro‐oxidant activity of Fe²⁺ in oxidation of cod phospholipids in liposomes

Abstract

This work examines how different factors such as temperature, amount of injected Fe 21, lipid concentration, pH, concentration of NaCl and concentration of dissolved oxygen influenced the lipid oxidation rate of liposomes made from cod phospholipids. The rate of lipid oxidation was measured by consumption of dissolved oxygen by liposomes in a closed vessel. The rate of oxygen consumption in liposomes was proportional to the concentration of iron and the lipid concentration in the assay mixture. The oxygen consumption rate was dependent on pH, with a maximum observed between pH 4 and 5. The addition of salt (final concentration 0.04-0.8 M) decreased the rate of oxygen consumption. The rate of oxidation was independent of the concentration of dissolved oxygen (in the range of 230-5 mM). The oxygen consumption rate followed Arrhenius kinetics, and the variation in activation energy found (60-87 kJ/ moles6K) might be due to variations in the composition of raw materials used in the experiments and different susceptibility to oxidation.

Oxidation of cod phospholipids in liposomes: Effects of salts, pH and zeta potential

“…Mabrouk and Dugan [23] explained the inhibition effect of NaCl on the oxygen uptake rate in emulsions by a decreased solubility of oxygen. However, in these studies, and as reported in our earlier studies, the oxygen uptake rate was constant at oxygen concentrations between 200 and 5 mM [14], and the reduction in the concentration of dissolved oxygen at 0.15 M NaCl is only 5% [24]. Mei et al [4] proposed that the ability of NaCl to decrease oxidation, at low iron concentration, could be due to the ability of NaCl to remove iron from the emulsion surface.…”

“…Lipid classes were determined by thin-layer chromatography (TLC) [15] and detected by an Iatroscan TLC-flame ionisation detector (FID) system (TLC-FID analyser TH-10 MK-IV; Iatron Laboratories, Tokyo, Japan) as described by Mozuraityte et al [14]. Two replicate analyses were performed and the results were expressed in area% as the mean value.…”

“…Phospholipids were isolated from total lipids using the acetone precipitation method [13], with a few modifications as described by Mozuraityte et al [14].…”

“…Liposomes were made as described by Mozuraityte et al [14]. Phospholipids were sonicated in a 5 mM 2-morpholinoethanesulfonic acid (MES; Sigma) buffer, pH 5.5, with an MSE Ultrasonic Disintegrator Mk2 (MSE Scientific instruments, Sussex, UK), at a lipid concentration of 30 mg/mL.…”

Production of High Quality Fish Oil by Thermal Treatment and Enzymatic Protein Hydrolysis from Fresh Norwegian Spring Spawning Herring By-Products

“…The decrease in stability from 60 to 80 °C could be explained by the increase in lipid oxidation rate with increasing processing temperature (Carvajal et al, 2009;Mozuraityte et al, 2006). Lipid oxidation leads to the formation of peroxides that can decompose to lipid radicals and lead to formation of secondary products, thus shortening the induction period.…”