Preparation and Stability of Pickering Double Emulsion Based on Xanthoceras sorbifolia Bunge Oil and Nanocellulose

A type of Pickering double (W₁/O/W₂) emulsion system based on Xanthoceras sorbifolia Bunge oil and nanocellulose was developed, and its stability was evaluated. A 1% (w/v) sodium alginate solution, polyglycerol polyricinoleate, Xanthoceras sorbifolia Bunge oil, and nanocellulose were used as the inner aqueous phase (W₁), inner interfacial emulsifier, intermediate oil phase, and outer emulsifier, respectively. The whole emulsion system was dispersed in the outer aqueous phase (W₂). Evaluation indicators included the microstructure, apparent viscosity, thermal stability, centrifugal stability, freeze-thaw stability, and layered appearance of the double emulsion. The five variable factors were polyglycerol polyricinoleate concentration, the volume ratio of the inner aqueous phase (W₁) to the oil phase (O), the volume ratio of the first emulsion (W₁/O) to the outer aqueous phase (W₂), and the types and concentrations of nanocellulose. Obvious differences in the microstructure and hydrophobicity of nanocelluloses were observed using a scanning electron microscope and contact angle measuring instrument. The cellulose nanofiber, possessing a large aspect ratio and network-like structure, displayed the strongest hydrophobicity. The double emulsion system displayed a high encapsulation rate and stable structure under the following conditions: concentration of polyglycerol polyricinoleate of 2.5% (w/v), W₁:O ratio of 3:7 (v/v), (W₁/O):W₂ ratio of 2:8 (v/v), and concentration of cellulose nanofiber as the outer emulsifier of 0.3% (w/w). When compared to two other types of cellulose nanocrystals, the cellulose nanofiber showed a stronger emulsification stability of the double emulsion. The successful construction and structural stability of the double emulsion were then proven by laser scanning confocal microscope observation, and the chemical stability was verified by the acid value and peroxide value of oil in the double emulsion. The Pickering double emulsion with solid microparticles of nanocellulose as the emulsifier and Xanthoceras sorbifolia Bunge oil as the encapsulated oil phase could serve as an effective delivery vehicle for novel functional ingredients.