Relationship between the Emulsion Stability and Phospholipid Distribution in the Aqueous Phases Inside and Outside of an Emulsion Droplet

Abstract

The distribution of phospholipids between the inside and outside of an emulsion droplet was studied in relation to the emulsion stability. The emulsion was prepared with various mixtures of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC), n-decane and water containing HC1, NaCl or NaOH. ¹³P-NMR spectra of the emulsion in the presence of lanthanide ion Pr³⁺ allowed quantitative measurement of the phospholipids in the internal and external aqueous phases, and in multilamellar vesicles. By a phospholipase A₂ treatment of PC facing the continuous aqueous phase, most of the internal phospholipids were suggested to be composed of PC. The ratio of the phospholipids inside and outside changed with the emulsifying conditions, and was well correlated with the emulsion stability. Thus, it is suggested that the phospholipid distribution in the emulsion of PC and LPC showed the change of their hydrophile-lipophile balance and of the interfacial absorption force.