Phosphatidylcholine-depleted lecithin as low-HLB emulsifier in double emulsions: A sensitivity analysis

Abstract

Phosphatidylcholine-depleted (PC-depleted) lecithin is characterized by a lower phosphatidylcholine/phosphatidylethanolamine (PC/PE) ratio, favoring the formation of water-in-oil (W/O) emulsions, and thus can be applied in water-in-oil-in-water (W/O/W) double emulsions (DEs). However, up to now, only a limited number of studies have described the use of PC-depleted lecithin in double emulsions. In this study, the influence of the formulation and processing conditions on the formation and stability of PC-depleted lecithin stabilized-DEs was investigated. The characterizations of DEs involved morphology, droplet size, viscosity, and entrapped water yield. The experimental results indicated that the incorporation of glucose in the water phase instead of potassium chloride (KCl) increased both the droplet size and the entrapped water yield in DEs, whereby the latter was increased by around 65% as compared to DEs containing 100 mM KCl. Reducing the salt content also facilitated the formation of DEs. Moreover, a correlation between the oil type and the 1st homogenization method was found: whereas DEs formulated with high oleic sunflower oil were always unstable irrespective of the emulsification method used, stable DEs were produced by the combination of medium-chain triglyceride oil and a rotor-stator system whereby microfluidization caused phase inversion. In addition, PC-depleted lecithin could stabilize up to 60% of water in oil. Meanwhile, stable DEs with a maximum internal water fraction of 24.1% were obtained by adjusting the original W/O/W ratio to 25/25/50. Finally, DEs stabilized by PC-depleted lecithin showed a comparable stability to those stabilized by polyglycerol polyricinoleate (PGPR) during 28 days of storage. To sum up, this work provides a better understanding of the sensitivity of PC-depleted lecithin-stabilized W/O/W emulsions towards the applied formulation conditions.