Zein-gelatin-based bicontinuous bigels co-regulated by aqueous phase microenvironment and dynamic oil-to-water ratio: From intermolecular interactions to structural and fat replacement properties.

Bicontinuous bigels are promising solid fat replacers, but their inherent thermodynamic metastability easily causes phase separation and structural collapse. Existing strategies mostly rely on passive adjustment of phase volume ratios or single gelator concentrations. To address this limitation, this study proposed an active regulation strategy targeting the aqueous phase microenvironment to achieve controllable and stable bicontinuous phases. With Zein-gelatin (GA) hydrogels and beeswax-glycerol monostearate (GMS)-medium chain triglyceride (MCT) oleogels as materials, the regulatory effects of Zein-to-GA mass ratios (0:10 to 8:2) coupled with dynamic oil-to-water ratios (4:6 to 6:4) on bigel structure and properties were systematically investigated. Results demonstrated that the introduction of Zein endowed bigels with a uniform interpenetrating bicontinuous microstructure. At a 4:6 Zein-to-GA mass ratio and a 5:5 oil-to-water ratio, the system exhibited excellent mechanical and rheological properties via the synergy of hydrogen bonds, hydrophobic interactions and covalent cross-linking. The hardness (1006.93 g), cohesiveness (0.87), gumminess (874.70), water-holding capacity (WHC, 79.63%), and oil-holding capacity (OHC, 82.63%) all peaked. After application in reduced-fat chocolate sauce, the total fat content (TFC) decreased to 22.46% with a fat reduction rate (FRR) of 49.81%, and the product exhibited excellent spreadability. After 30 days of storage, the peroxide value (PV) was 0.62 meq/kg and the thiobarbituric acid reactive substances (TBARS) value was 1.89 mg/kg, indicating good lipid oxidation stability. This study confirms that aqueous phase microenvironment regulation is an effective strategy to stabilize bicontinuous bigels, providing theoretical support for their reduced-fat food applications.