Effect of the dispersed state of phospholipids on emulsification—Part 1. Phosphatidylcholine

In this study the effect of the dispersed state of soy phosphatidylcholine on emulsification is investigated. The emulsifier is either dispersed in the aqueous phase (coarsely, as small vesicles, as large vesicles), or it is dispersed in the oil phase. Oil-in-water emulsions are prepared with the emulsifier present in the different dispersed states. High-pressure homogenization is used for the emulsification and the impact of pressure, number of passes through the homogenizer and emulsifier concentration is investigated by determination of droplet size and surface loads. Pre-emulsions made using a rotor-stator mixer have a smaller average droplet diameter when the emulsifier is dispersed in the oil phase than in the aqueous phase whereas the smallest droplets are obtained with small vesicles when high-pressure homogenization and repeated passages is used. Moreover, the droplet size can be significantly decreased by increasing the number of passages while an increased pressure has a smaller effect on droplet size. Hence, for a slow adsorbing emulsifier, repeated passages through the homogenizer may be more efficient since successive adsorption can occur. The surface loads, adsorption yields and emulsification efficiencies are observed to depend on the emulsification conditions and dispersed state of the emulsifier. The results from this study illustrates that the dispersion of the emulsifier may have a significant impact on emulsification and, hence, it may be important to consider the dispersed state of the emulsifier in order to achieve desired emulsion properties.