Sequestering and exchange of metal ions in edible oils containing phospholipids

Metal ions (Zn 2+ and Fe 3+ ) are transferred from water into vegetable and marine oils when these oils contain phospholipids. Ions present in the oil may be exchanged with the same or with other kinds of cations in a water phase in contact with the oils. Radioactive isotopes of zinc and iron were used for measuring the exchange rate. The sequestering action by the oil strongly depends on the contents of phospholipids and reaches a maximum (ions v/s phospholipids) in the concentration range between 3 and 60 ppm of phospholipids (0.1–2 ppm of phosphorus) in the oil. The same sequestering effect is demonstrated when purified phospholipids (phosphoethanolamine and acetone‐refined soybean lecithin) are added to edible oils from which the natural content of phospholipids has been removed. Free fatty acids do not appear to sequester multivalent ions nor to influence the sequestering action by the phospholipids when added to the oil.