A bigel is a biphasic system that is composed of an organogel and hydrogel. Bigel advantages in comparison to both types of gels alone include greater stability, better skin compatibility, and the ability to carry lipophilic and hydrophilic substances. The objective of this study was to characterize the thermal, mechanical and structural properties, as well as chemical interactions between components of formulated bigels. A combination of a gelatin hydrogel and rice bran wax-based organogel with soybean oil as the continuous phase was used for bigel preparation. Bigels were formulated with different hydrogelator (gelatin) concentrations and organogel to hydrogel (OG:HG) ratios. Two gelatin concentrations (5 and 7 wt%) were used to prepare four bigels (for each concentration) of varying OG:HG ratios (50:50, 40:60, 30:70, 20:80). The organogelator concentration remained as 10 wt% rice bran wax for all samples. Bigels were analyzed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), confocal laser scanning microscopy (CLSM) and small deformation rheology. Confocal microscopy images confirmed an organogel-in-hydrogel system for all OG:HG ratios. An increase in organogel content increased the interaction between organogel droplets, leading to a more structured bigel. This was also confirmed by rheology frequency sweeps where 50:50 and 40:60 ratios had the highest storage (G’) modulus values. FTIR and DSC showed no unique peaks from interaction between components meaning the system is a “true” bigel that is kinetically stable. A modified Boltzmann Sigmoidal equation fit the model rheological behavior of the samples. The successful characterization of this system can be used to tailor its properties for specific applications in the food, pharmaceutical and cosmetic industries.
