Influence of stearylamine and dicetylphosphate on the physical properties of submicron O/W emulsions.

Stearylamine and dicetylphosphate were added to glycerol or sorbitol isotonised sunflower oil, soybean oil and medium chain triglyceride (MCT) oil-in-water submicron emulsions stabilised using egg yolk and soybean lecithins, and blends of polysorbate/sorbate with the aim to induce positive and negative electrical charges. Glycerol isotonized emulsions containing 0.3% (w/w) stearylamine could only be obtained when lecithins dosing up to 80% (w/w) phosphatidylcholine (PC) were employed, but they did not resist to long term storage up to 90 days. Sorbitol isotonized stearylamine emulsions were achieved only with lecithins having a PC content superior to 90% (w/w) without more resistance to storage. Stearylamine did not influence the stability of emulsions prepared with non-ionic emulsifiers. So, the destabilising effect of stearylamine on emulsions prepared with lecithins could be due to interaction of its cationic group with anionic lipids and was not related to the nature of the oil. Dicetylphosphate did not markedly affect emulsions supporting further the hypothesis of interaction of stearylamine with lecithin phospholipids.