Design of bigel-based co-delivery systems for lipophilic/hydrophilic nutraceuticals: Focus on rheological properties and in vitro digestive performance

This study provides valuable insights into the structural and functional characteristics of bigels containing hydrophilic (catechin, CAT) and lipophilic (curcumin, CUR) compounds, emphasizing the relationship between their rheological properties and digestive behavior. By adjusting the oleogel-to-hydrogel (OG-to-HG) ratios, bigels were tailored to exhibit distinct mechanical properties and digestion behaviors. The bicontinuous structure formed at a 5:5 OG-to-HG ratio (sample O5H5) exhibited delayed lipolysis and enhanced bioaccessibility of CUR (68.16% ± 1.78%) and CAT (56.16% ± 1.78%). This was supported by its high thixotropic recovery rate (76.43% ± 0.10%), longest delay time (λret = 12.33 ± 0.44 s), and optimal stress-stiffness ratio (S value = 0.81 ± 0.02), outperforming other structural configurations (OG-in-HG and HG-in-OG). This structure hinders the accessibility of digestive enzymes and bile salts, thereby slowing the breakdown of the lipid phase. Correlation analysis indicated strong positive relationships between the creep recovery rate and both the free fatty acid (FFA) release rate (r = 0.98, p