Bilayer electrostatic deposition: An effective strategy to enhance physical stability of double emulsion

In order to surmount the limitations of W1/O/W2 double emulsions, a novel ovalbumin fibrils (OVAF)/pectin-based bilayer-stabilized W1/O/W2 double emulsion (OP-BDE) was designed. Atomic force microscope verified the successful preparation of OVAF, and three-phase contact angle measurement showed that OVAF had great potential to stabilize W1/O/W2 double emulsions. The OVAF-based monolayer-stabilized W1/O/W2 double emulsion (O-MDE) was prepared with OVAF as the outer emulsifier, and the effects of polyglycerol polyricinoleate (PGPR) content, oil fraction and OVAF concentration on the formation of O-MDE were systematically studied. Afterwards, the OP-BDE was prepared by layer-by-layer electrostatic deposition (LBL) technology, and the effects of the ratio of pectin to O-MDE as well as pectin concentration on the formation of OP-BDE were investigated. Moreover, the physicochemical properties of O-MDE and OP-BDE were also characterized by micro-morphology, zeta potential and rheological behavior. In addition, the effects of pH, freeze–thaw cycle and heat treatment on properties of the emulsions were examined. The results revealed that the physical stability of OP-BDE was significantly improved compared with O-MDE. Besides, the storage stability of OP-BDE was the best when pH was 3.5. Rheological results indicated that the adsorption of pectin could improve the viscosity of O-MDE. This research may be of great implications for the design of new W1/O/W2 double emulsions with preferable physicochemical properties.