Viscosity of phosphatidylcholine (lecithin)

Abstract

The viscosities of egg lecithin dispersed in water have been measured by means of a Couette viscometer. The more concentrated dispersions are thixotropic, but below 1·8% w/w of lecithin the sols become Newtonian. From the extrapolated ratio of specific viscosity to volume fraction, the dispersed particles are considered to be of an elongated rod-like shape. When the coarse dispersions of lecithin are irradiated ultrasonically, an irreversible clearing of the sols occurs, accompanied by a big decrease in viscosity. None of the irradiated sols examined was thixotropic and the extrapolated viscosity ratio indicated a low asymmetry and degree of hydration for the dispersed particles. The effect of ultrasonic irradiation is not only to reduce size and asymmetry of the aggregates but also to expel water from them.