Fabrication of nanocrystal/β-lactoglobulin complexes stabilized W1/O/W2 emulsions: Structure, stabilization mechanism and application for co-encapsulation of curcumin and EGCG

Compared with traditional single emulsions, the distinct three-phase and two-interface structures of double emulsions enable them to simultaneously encapsulate and deliver hydrophilic and lipophilic compounds, which significantly broadens their applications. Here, cellulose nanocrystal (CNC)/β-lactoglobulin (β-LG) complexes and polyglycerol polyricinoleate (PGPR) were used to fabricate water-in-oil-in-water (W/O/W) emulsions. We first examined the influence of different PGPR concentrations (1.0, 3.0, 5.0, and 7.0 wt%) and O:W 1 mass ratios (9:1, 8:2, 7:3, and 6:4) on the stability of the primary W 1 /O emulsions. Building on this, the influence of different W 1 /O:W 2 mass ratios (1:9, 2:8, 3:7, and 4:6) on W 1 /O/W 2 emulsions was studied. We then utilized laser confocal microscopy to explore the internal environment of the emulsions and employed urea and sodium dodecyl sulfate as interventions to analyze the interactions at their interfaces. Finally, curcumin and epigallocatechin gallate were selected as model hydrophobic and hydrophilic nutrients, respectively, to confirm the promising applications of the W 1 /O/W 2 emulsion. Their encapsulation efficiencies reached 95.7 % and 86.8 % when co-loading in the W 1 /O/W 2 emulsion. Additionally, in vitro simulated digestion revealed that nutrients remained protected throughout oral and gastric stages, with controlled release occurring upon intestinal arrival, and their bioaccessibility was enhanced to 65.1 % and 71.6 %, respectively. The W 1 /O/W 2 emulsions we prepared and the elucidation of their underlying mechanisms have presented new possibilities for developing food and delivery systems in the future.