Carob-Based Bigel Microstructure Modulates the Gastrointestinal Release of D-Pinitol, Phenolics and Lipids

Carob-based bigels (BGs) were developed as structured fat replacers and delivery systems for bioactive compounds during gastrointestinal digestion. Four formulations combining different hydrogel (HG)/oleogel (OG) ratios and selective incorporation of two carob extracts—an inositol-rich extract (I-CFE) in the HG phase and a phenolic-rich extract (P-CFE) in the OG phase—were evaluated to determine the influence of microstructure on digestive behavior and bioactive release. Confocal microscopy showed that BG structure was mainly governed by the OG network, while alginate-rich aqueous domains remained dispersed and confined to different extents depending on formulation. This organization strongly influenced hydration, enzyme accessibility and matrix breakdown during digestion. D-Pinitol remained stable throughout gastrointestinal digestion, and its release depended on the accessibility of hydrated aqueous domains. Phenolic release and antioxidant activity were also modulated by matrix architecture and extract localization, with BG-70/30-I+P showing the most efficient and sustained antioxidant response. Lipid digestion and fatty acid bioaccessibility were similarly influenced by BG structure: less compact OG networks promoted greater lipase accessibility and higher bioaccessibility of unsaturated fatty acids, whereas more structured lipid matrices partially restricted lipolysis. Overall, BG functionality was governed primarily by microstructural organization rather than composition alone.