Effect of W/O pre-emulsion prepared with different emulsifiers on the physicochemical properties of soy protein isolate-based emulsion films

The effects of incorporating a water-in-oil pre-emulsion based on different emulsifiers with similar hydrophilic-lipophilic balances on the physicochemical properties of soy protein isolate-based emulsion films were investigated. Confocal laser scanning microscopy images indicated that the oil droplet size in the polyglycerol polyricinoleate and lecithin pre-emulsions was larger than that in the glycerol monostearate, span, and sucrose ester pre-emulsions. By contrast, the oil droplet size in the film-forming emulsions had opposite orders. After drying, the polyglycerol polyricinoleate and lecithin emulsion films contained small and evenly distributed oil droplets and demonstrated a small difference of upper and lower surfaces in oil concentration and contact angle. The water vapor permeability of emulsion films prepared by polyglycerol polyricinoleate and lecithin pre-emulsion was 2.35 × 10 −10  g m −1  s −1  Pa −1 and 2.32 × 10 −10  g m −1  s −1  Pa −1 , respectively, lower than that of other emulsion films. The control emulsion films had the highest tensile strength of 7.43 MPa, whereas polyglycerol polyricinoleate emulsion films had the lowest tensile strength of 4.87 MPa. Furthermore, the polyglycerol polyricinoleate emulsion films had the lowest glass transition temperature among the prepared emulsion films. This study concluded that the properties of film-forming emulsions could be affected by pre-emulsions based on different emulsifiers, resulting in different physicochemical properties of the emulsion films.