Evaluation of different emulsification methods in double emulsion systems: Response surface optimization approach and emulsion properties

Abstract

Double emulsions have been the focus of several studies due to their advantages such as trapping dispersed phase droplets, delaying the release, masking taste-odor, and providing protection against oxidation. In this study, double emulsions (w/o/w) were prepared by different emulsifying methods including one-step, two-steps and membrane methods to assess their emulsion yield and stability. Results showed that one-step method was preferable for zeta potential and polydispersity index but similar in droplet size as in membrane method. Due to its simplicity and ease of use, one step method was further studied in an optimization study to evaluate factors affecting droplet size and polydispersity index. Under optimum conditions (oil ratio: 35.1%, emulsifier ratio: 6.9%, homogenization speed: 15000 rpm and homogenization time: 5 min), droplet size and polydispersity index were 180.7±6.6 nm and 0.13±0.01, respectively. pH of the resultant emulsion was 2.89±0.01, conductivity was 9.65±0.05 mS/cm, emulsion stability was 8.02±0.66%, and zeta potential was -50.30±1.70 mV. This study demonstrated that nano-scale emulsion and highly stable emulsions can be obtained for various applications in the food industry under optimum conditions by a single-step method.