Bigels as co-delivery system for dysphagia food: Effects of the wax oleogelator type and bigel structure on the gastrointestinal release behaviour of bioactive compounds

This study investigated the design of bigel co-delivery systems employing gelatin hydrogel and oleogels with lacquer wax (LW), beeswax (BW) or mixed wax (MW) as an oleogelator. The typical T 2 relaxation signals in low-field NMR analysis and microscopic observations indicated that the bigels transitioned from O/H to H/O structure as the hydrogel/oleogel ratio decreased from 8:2 to 6:4, and utilizing MW could obtain bicontinuous structure at a hydrogel/oleogel ratio of 7:3 under our experimental conditions. Polarized microscopic images and XRD analysis revealed that BW-based bigels formed larger needle-like lipid crystals with a β′ form, whereas LW induced smaller β crystals and MW promoted the formation of both β and α polymorphs with intermediate size. This led to the greater elastic modulus (3518-463600 Pa) and hardness (237-1347 gf) of BW-based bigels compare to those containing LW (elastic modulus: 2255-256600 Pa; hardness: 172-317 gf). FTIR analysis indicated no chemical interactions between the gelatin hydrogel and different oleogels. All the bigels presented textural attributes and standardized dysphagia test results (level 6: soft & bite-sized) satisfying the requirement of dysphagia-friendly foods. In vitro digestion assays demonstrated that lower hydrogel/oleogel ratio and the use of BW contributed to reduced release rates of EGCG and Cur. However, when the hydrogel/oleogel ratio was fixed at 7:3, the use of MW resulted in the lowest release rates of EGCG (40.87% ± 0.48%) and Cur (15.15% ± 1.78%) due to the bicontinuous microstructure. These findings provide broader ideas for developing functional foods to accommodate the needs of dysphagia patients.