Development of Novel Rice Bran Wax/Gelatin-Based Biphasic Edible Gels and Characterization of their Microstructural, Thermal, and Mechanical Properties

The aim of this study was to develop and characterize the mechanical, microstructural, and thermal behavior of a novel edible biphasic gel system also termed bigel. A combination of a gelatin hydrogel and rice bran wax (RBW)-based oleogel with soybean oil was used for bigel formulation. Bigels were prepared with four oleogel-to-hydrogel (OG:HG) ratios (50:50, 40:60, 30:70, 20:80) at three gelatin concentrations (5, 7, and 10% (w/w)). The RBW concentration remained constant at 10% (w/w). Bigels were analyzed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), confocal laser scanning microscopy (CLSM), and small deformation rheology. CSLM images confirmed an oleogel-in-hydrogel system for all bigel formulations with an increase in oleogel proportion leading to increased oleogel droplet size and enhanced stability. Rheological characterization of the systems showed all bigel formulations, regardless of gelatin concentration and oleogel to hydrogel proportion, showed more solid than liquid (G ' > G '') character and frequency independence at 20 celcius. Bigels with higher OG:HG ratios, i.e., 50:50 and 40:60, consistently exhibited greater elastic modulus (G ') values than those of gels with lower OG:HG ratios, providing evidence of increased oleogel droplet interaction leading to enhanced mechanical properties. The rheological behavior of all bigels was accurately captured by the Boltzmann Sigmoidal model. FTIR and DSC analysis showed distinct peaks for the oleogel and hydrogel phases in all bigel samples with the absence of new thermal events, indicating a lack of interactions between components of both phases. Overall, the system is a "true" bigel that benefits from its two distinct phases and is kinetically stable.