Synergistic stabilization of O/W/O double emulsions: Role of gelatin and beeswax-soybean oil in enhancing structural integrity and rheological properties

The stabilization of double emulsions (e.g., oil-in-water-in-oil or water-in-oil-in-water emulsions) remains a research challenge due to their simultaneous possession of two distinct oil-water interfaces. In this study, a novel oil-in-water-in-oil (O/W/O) double emulsion was constructed utilizing a beeswax-soybean oil oleogel as the continuous phase, while a gelatin-stabilized oil-in-water (O/W) emulsion served as the dispersed phase. The effects of gelatin concentration, beeswax content, and the volume fraction of the dispersed phase on the stability, microstructure, and rheological properties of the O/W/O double emulsions were investigated. The results indicated that the emulsion droplet size reduced from 10.08 ± 2.29 μm to 6.92 ± 1.82 μm by elevating the gelatin concentration. In addition, the solidification of the O/W/O double emulsion into an oil-solid-solid interface structure induced by thermal treatment and subsequent storage at room temperature, which resulted in improved stability and modulus. Following freeze-thaw cycles, the stability of the double emulsions remained unaffected by varying concentrations of beeswax (ranging from 2 to 8 wt%). Destabilization was observed only when the volume fraction of the O/W emulsion reached 55 % v/v, suggesting that double emulsions with lower internal dispersed-phase contents (e.g., 10 % v/v and 25 % v/v) exhibited superior freeze-thaw stability. These findings highlight the potential of this innovative formulation for producing interfacially stable O/W/O double emulsions with enhanced physical properties, thereby offering a promising strategy for applications that necessitate long-term stability and structural integrity.