Phase inversion regulates the rheology, 3D printability, and co-delivery functions of cellulose nanofibril/beeswax bigels.

Abstract

Bigels are promising for functional foods, 3D printing, and the co-delivery of hydrophilic and hydrophobic bioactives. Therefore, regulating their properties is important for practical applications. In this work, cellulose nanofibril (CNF)/beeswax bigels were constructed, and the relationships between continuous phase and their microstructure, rheological properties, 3D printability, and delivery performance were investigated. Microscopic observations showed distinct phase organizations, while spectroscopic analysis indicated no evident new covalent bonding during bigel formation. Rheological and textural analyses demonstrated that different continuous phase organizations resulted in distinct mechanical responses of the bigels. With increasing oleogel content, hardness increased from 10.00 ± 0.22 g to 14.50 ± 0.36 g, whereas springiness decreased from 1.83 ± 0.15 mm to 1.03 ± 0.08 mm, reflecting the transition from flexible and recoverable structures to more rigid and supportive structures with increasing oleogel dominance. All bigels showed desirable 3D printability and relatively high encapsulation efficiencies for curcumin (Cur) and proanthocyanidins (PAC), with values above 86% and 75%, respectively. O/W-type bigels exhibited stable extrusion at relatively lower pressure (0.032 MPa), whereas W/O-type bigels required higher pressure (0.036 MPa) with enhanced structural support. W/O-type bigels showed stronger photothermal protection and slower release behavior, with final Cur and PAC releases of 54.4% and 60.7%, respectively, whereas O/W-type bigels showed faster release (84.0% for Cur and 81.2% for PAC). The biphasic bigel exhibited balanced printing and delivery performance. These findings provide a strategy for designing 3D printed food matrices with tunable properties and release behaviors through adjustment of bigel phase structures.