Effect of carboxymethyl cellulose incorporation to gelatin-sunflower oil bigel on the physicochemical and structural properties

Bigels are innovative and appealing heterogeneous matrices composed of two structured-gel (hydrogel and oleogel) phases, which suitable for the entrapment of both hydrophilic and lipophilic active agents. As structuring the bigel phases using convenient materials can enhance the main characteristics, this study aimed to develop bigel system based on a hybrid hydrogel consisting of gelatin and carboxymethylcellulose (CMC). The impact of incorporating various concentrations of CMC (0, 0.5, 1, 2, and 3% w/w) into gelatin-based hydrogel at a constant organogel/hydrogel ratio of 60:40 was investigated on bigel properties. The integration of gelatin and CMC significantly affected the solvent holding capacity (SHC), microstructure, rheology, thermal, and textural properties. The results showed that bigel samples containing gelatin-CMC had lower SHC compared to gelatin-based samples. The integration of CMC to bigel formulation resulted in a significant decrease in hardness, cohesiveness, and adhesiveness also smooth texture. Differential scanning calorimeter (DSC) analysis of the bigels showed a descending trend in melting point from 99.07 to 98.60°C for bigel samples as the CMC concentration increased from 0% to 2%. This was followed by an increase in melting temperature (100.95°C) in the bigel containing 3% CMC. Particle size distribution data indicated that the droplet sizes of the bigels increased with the incorporation of CMC into the hydrogel phase, without displaying a distinct concentration-dependent trend. The rheological characteristics of strain sweep, frequency sweep, and loss factor affected by gelatin/CMC concentration. Overall obtained results highlight that CMC incorporation to gelatin plays a crucial role in bigel offering different textural, rheological and thermal properties. So that carefully selection and optimization of gelatin and CMC concentrations in hydrogel phase are essential for tailoring the mechanical strength and stability of bigels for various applications such as drug delivery, cosmetic, and food industries. Regarding the desired properties of CMC, it could be recommend to use by combination with gelatin to create a structure–function aimed bigels.