Food-Grade Bigels Enable Targeted Ferulic Acid Release

Researchers published a study in Food Science & Nutrition describing the development of novel bigel formulations designed to carry ferulic acid, a phytochemical found in vegetables with antioxidant and anti-inflammatory properties. The study, led by a team based in Kermanshah, Iran, focused on creating a dual-network structure that combines a chitosan and sodium caseinate hydrogel with a soy lecithin and beeswax oleogel. This approach aims to address the poor solubility, stability, and bioavailability of ferulic acid, which currently limits its incorporation into food products. The authors describe this as the first report of a bigel system integrating these specific components for targeted delivery of ferulic acid in food-grade applications.

The study utilized food-grade ingredients, specifically chitosan, sodium caseinate, soy lecithin, and beeswax, which are generally recognized as safe. Chitosan is a linear polysaccharide derived from chitin, known for its biocompatibility and antimicrobial properties, while sodium caseinate is a water-soluble protein derived from milk casein. The combination of these two biopolymers allows for a hydrogel phase that exploits polysaccharide-driven network stability and protein-mediated interfacial functionality. The oleogel phase was formed using soy lecithin and beeswax, which act as gel-forming agents to create a semisolid structure capable of encapsulating lipophilic compounds.

The experimental design involved preparing seven distinct bigel samples to systematically investigate the effects of beeswax concentration and the ratio of chitosan to sodium caseinate. Five samples contained 7% beeswax by weight, with varying chitosan-to-sodium caseinate ratios ranging from 100:0 to 0:100. Two additional samples were prepared with lower beeswax concentrations of 5% and 3%, both using a balanced 50:50 ratio of the biopolymers. This matrix allowed the researchers to isolate the impact of the oleogel strength and the hydrogel composition on the overall structural and functional properties of the bigels.

Physical characterization revealed that the bigels exhibited non-Newtonian, shear-thinning behavior, which is advantageous for processing while maintaining structural stability during storage. Rheological measurements indicated that all samples displayed elastic-dominant behavior, with the storage modulus exceeding the loss modulus. Sample BG4, which contained 100% chitosan and 7% beeswax, demonstrated the highest viscosity and structural strength, attributed to a dense, well-structured internal network. In contrast, sample BG7, with 3% beeswax and a 50:50 biopolymer ratio, showed the lowest viscosity, suggesting a weaker network formation.

Swelling ratio measurements highlighted an inverse relationship between beeswax concentration and water uptake. The sample with the highest beeswax content and pure chitosan hydrogel exhibited the lowest swelling ratio of 10.8%, while the sample with the lowest beeswax content showed the highest swelling ratio of 22.3%. The crystalline and lipophilic structure of beeswax appears to act as a physical barrier against water diffusion, restricting the expansion of the gel network. This reduced swelling in compact networks is consistent with the observed higher viscosity and elastic behavior in those formulations.

Fourier transform infrared spectroscopy provided molecular evidence of interactions between the hydrogel and oleogel phases. The spectra revealed characteristic bands from all components, with peak shifts and intensity changes suggesting the presence of secondary interactions such as hydrogen bonding and electrostatic attractions. These interactions are critical for stabilizing the physically interpenetrated dual-network structure. The presence of a peak at 3007 cm⁻¹, attributed to the phenolic structure of ferulic acid, confirmed its successful incorporation and potential for hydrogen bonding with both the hydrophilic and lipophilic phases of the bigel.

Scanning electron microscopy observations classified the bigel system as a hydrogel-continuous matrix with dispersed oleogel domains. The microstructure varied significantly depending on the formulation. Sample BG4 displayed fine, closely packed particles, indicating a highly compact gel network that likely restricts the diffusion path for ferulic acid. Conversely, sample BG7 showed a heterogeneous structure with dispersed droplets, reflecting a weaker and less stable network. These microstructural differences correlate with the rheological and swelling data, where compact and homogeneous networks exhibited higher structural strength and lower swelling.

In vitro gastrointestinal release studies assessed the performance of the bigels in simulated gastric and intestinal fluids. The release of ferulic acid was analyzed over two hours in each phase. Samples with lower beeswax content generally exhibited higher release rates in both phases, likely due to a less dense network that allows for greater fluid penetration. Kinetic modeling of the release data indicated that the process was not governed by a single transport mechanism. The Korsmeyer-Peppas model provided a high fit, with release exponent values close to unity, suggesting that polymer relaxation and structural rearrangement of the bigel matrix contributed significantly to the release of ferulic acid alongside diffusion.

The release behavior showed a distinct phase-dependent response to the biopolymer composition. During the gastric phase, higher proportions of sodium caseinate correlated with reduced ferulic acid release, possibly because the protein approaches its isoelectric point in acidic conditions, leading to aggregation and decreased matrix relaxation. In contrast, higher chitosan content enhanced release in the gastric phase due to the protonation of amino groups, which increases polymer hydration and chain mobility. This trend reversed during the intestinal phase, where higher sodium caseinate content resulted in increased release, attributed to improved hydration and enzymatic degradation of the protein by proteases.

After two hours of each digestion phase, approximately 60% to 90% of the ferulic acid was released across all samples. Sample BG7, with its lower beeswax content and porous structure, achieved the highest release rate of around 90%. Sample BG4, containing the highest chitosan content, exhibited the lowest release rate of approximately 60%, consistent with its denser polymer network that restricts molecular mobility. These findings indicate that adjusting the beeswax content and the chitosan-to-sodium caseinate ratio can effectively modulate the release profile, allowing for targeted delivery in specific gastrointestinal environments.

The study concludes that the dual-network architecture of the bigels offers a balanced combination of mechanical stability and controlled release behavior. The synergistic combination of the polysaccharide-protein hydrogel and the crystalline wax-based oleogel creates a system that is more robust than single-phase delivery systems. However, the researchers noted that encapsulation efficiency was not evaluated in this study, which is a limitation for understanding the full loading capacity of the system. Additionally, the study did not explore regulatory considerations, cost efficiency, or performance under industrial processing conditions.

Future investigations are required to validate the system under real-world conditions and assess its commercial feasibility. The use of food-grade ingredients suggests a favorable potential for large-scale production, but further studies on storage stability, thermal processing tolerance, and sensory attributes are necessary before practical industrial applications can be considered. This work highlights the potential of bigels for functional food applications where the protection and targeted delivery of bioactive compounds are essential.

Subject of Research: Development and characterization of chitosan/beeswax bigels for ferulic acid delivery

Article Title: Development and Characterization of Bigel Based on Chitosan/Sodium Caseinate Hydrogel and Soy Lecithin/Beeswax Oleogel as Carriers for Ferulic Acid

Article References: Kalantari, G., Valizadeh, F., & Abdolmaleki, K. (2026). Development and Characterization of Bigel Based on Chitosan/Sodium Caseinate Hydrogel and Soy Lecithin/Beeswax Oleogel as Carriers for Ferulic Acid. Food Science & Nutrition, 14(11), Article e72549. https://doi.org/10.1002/fsn3.72549

Image Credits: AI Generated

DOI: 10.1002/fsn3.72549

Keywords: ferulic acid, bigels, chitosan, beeswax, controlled release, food science, hydrogels, oleogels, nutraceuticals, biopolymer networks, Development, Characterization