Phospholipid-BasedReverse Micelle Structures in VegetableOil Modified by Water Content Free Fatty Acid and Temperature

摘要

Colloidal assemblies of phospholipids in oil are known to be highly sensitive to changes in system composition and temperature. Despite the fundamental biological and high industrial relevance of these aggregates, the mechanisms behind the structural changes, especially in real oils, are not well understood. In this work, small-angle X-ray scattering (SAXS) was combined with molecular dynamics simulations to characterize the effects of oleic acid, water, and temperature on self-assembled structures formed by lecithin in rapeseed oil. SAXS showed that adding water to the mixtures caused the precipitation of liquid-crystalline phases with lamellar or hexagonal geometry. The combination of SAXS and molecular dynamics simulations revealed that stable spherical reverse micelles in oil had a core radius of about 2 nm and consisted of approximately 60 phospholipids centered around a core containing water and sugars. The presence of oleic acid improved the stability of reverse micelles against precipitation due to the increase in the water concentration in oil by allowing thereverse micelle cores to expand and accommodate more water. The shapeand size of the reverse micelles changed at high temperatures, andirreversible elongation was observed, especially in the presence ofoleic acid. The findings show the interdependency of the structureof the reverse micellar aggregates on system composition, in particular,oleic acid and water, as well as temperature. The revealed characteristicsof the self-assembled structures have significance in understandingand tuning the properties of vegetable oil-based emulsions, food products,oil purification, and drug delivery systems.