Stability of water-in-oil-emulsions containing phosphatidylcholine-depleted lecithin

Water-in-oil (W/O, 30/70) emulsions were prepared with phosphatidylcholine depleted lecithin [PC/(PI;PE) = 0.16] as W/O emulsifier in sunflower oil. The composition of the aqueous phase was varied by adding sodium caseinate (SC), whey protein isolate (WPI), gelatine and/or xanthan and their effect on the particle size distribution as well as on the sedimentation of the water droplets was investigated. Furthermore, the influence of the emulsion components on the interfacial tension between the oil phase (MCT-oil) and water was characterised. The additives in the aqueous phase differently influenced the water droplet size, aggregation behaviour and storage stability of W/O emulsions prepared with the phosphatidylcholine depleted lecithin. Emulsions were more stable and smaller in droplet size when they contained WPI in water. The droplet size was further reduced by combining WPI with xanthan in the aqueous phase. In contrast, the addition of gelatine or SC resulted in an increase in water droplet size and rapid sedimentation of the dispersed water. The formation and stabilisation of W/O emulsions prepared with the phosphatidylcholine depleted lecithin was supported by the addition of WPI with medium surface activity at the W/O interface. In comparison, the proteins gelatine or SC, which rapidly reduce surface tension at W/O interfaces had a detrimental effect on W/O emulsions otherwise stabilized by lecithin. (C) 2005 Elsevier Ltd. All rights reserved.