A bigel is, at its core, a marriage of two gels that normally want nothing to do with each other. One phase is a hydrogel, a network of plant-derived polymers such as proteins or polysaccharides swollen with water. The other is an oleogel, an oil continuous phase trapped inside a solid-like scaffold built from gelators such as waxes, ethylcellulose, or plant sterols. Because both phases are immobilized in their own networks, the resulting material behaves like a solid or semi-solid yet contains substantial water and oil simultaneously. That combination lets formulators replace solid fats in products like spreads, sausages, and bakery items while also using the two compartments as chemically distinct cargo holds: hydrophilic bioactives dissolve into the hydrogel, lipophilic ones dissolve into the oleogel, and neither needs a synthetic solvent to stay put.

The review’s central claim is that this biphasic architecture functions as a release-mechanism regulator rather than a passive container. Three canonical morphologies dominate the literature: oleogel-in-hydrogel, in which oil droplets gelled internally are dispersed through a polymer matrix; hydrogel-in-oleogel, the inverse arrangement; and bicontinuous systems in which both networks interpenetrate. Each geometry favors a distinct digestive trajectory. An oleogel-in-hydrogel design tends to shield the lipid phase behind a swelling polymer wall, delaying contact between dietary lipases and the oil until the bolus reaches the small intestine. A hydrogel-in-oleogel configuration instead embeds the water-based payload inside a fat continuous phase, which can protect water-soluble compounds from the acidic, protease-rich environment of the stomach. Bicontinuous morphologies, meanwhile, offer intermediate pathways whose release kinetics can be steered by tuning the connectivity of each network.

Underlying these broad patterns are specific physical mechanisms that operate during gastrointestinal transit. The review emphasizes that parameters such as the hydrogel-to-oleogel ratio, the density of the oleogel network, and the design of the interface between the two phases modulate how accessible pancreatic lipase and bile salts are to the lipid fraction. When lipase and bile salts reach the oil phase easily, lipolysis proceeds quickly and any lipophilic cargo is liberated early. When the oil is locked inside a dense crystal network or behind a robust interfacial film, lipolysis slows, and release shifts toward the intestinal phase where absorption is most effective. On the aqueous side, the swelling and erosion behavior of the hydrogel network governs how quickly hydrophilic compounds diffuse out, with crosslink density and polymer composition acting as the primary dials.

Across the studies the authors compared, two design rules emerged with unusual consistency. Denser oleogel networks and better-stabilized interfaces reliably slow lipolysis and push release into the intestinal stage, meaning bioaccessibility can be engineered rather than left to chance. Phase architecture, in turn, dictates which payload enjoys protection: the phase that surrounds the other determines whether a hydrophilic or a lipophilic compound is the one shielded from premature exposure. This reframing matters because traditional single-phase delivery systems force formulators to choose one protection strategy for all cargo. In a bigel, a single spoonful of a functional spread could, in principle, carry vitamin D in its oil phase and vitamin C in its water phase, each released on an independently controllable schedule.

Interfacial engineering adds a third, largely independent design dimension. The review highlights three strategies: Pickering stabilization, in which solid particles such as protein or cellulose nanocrystals adsorb at the oil-water boundary and form a physical barrier; amphiphilic gelators that self-assemble into interfacial films; and polysaccharide-layer modification, in which charged biopolymers are deposited onto droplet surfaces to thicken or strengthen the boundary. Because these interfacial layers control how fast lipase, bile salts, and co-solutes can penetrate, they let formulators decouple the release rate from the bulk gelator selection. A wax chosen for its melting profile or clean label status no longer locks in a single release behavior; the interface can be tuned separately to slow or accelerate lipolysis as the application demands.

These structural choices translate into measurable digestive performance. Reported applications show improved encapsulation efficiencies for both hydrophilic and lipophilic bioactives, reduced gastric pre-release of compounds that would otherwise degrade or be absorbed prematurely, and antioxidant synergism when co-encapsulated compounds regenerate or protect one another. The dual-network architecture also acts as a physical barrier against oxidation, since each gelled phase limits oxygen diffusion into the compartment holding its oxidation-sensitive payload. For plant-based food developers, the appeal is twofold: the same material that replaces saturated fat also serves as a delivery vehicle, collapsing two formulation problems into one ingredient.

The review is candid about the obstacles standing between laboratory prototypes and commercial deployment. The most significant is the absence of unified quantitative frameworks that predict release behavior from compositional inputs. Formulators currently cannot feed a bigel recipe into a model and obtain a reliable release curve; instead, each system must be characterized empirically. Compounding this, the field relies heavily on static in vitro digestion models that mimic the mouth, stomach, and intestine in sequential beakers but lack the mechanical shear, enzymatic renewal, and absorption dynamics of a living gut. Without in vivo validation, the review warns, reported bioaccessibility figures may not survive contact with real digestive physiology.

Standardization of characterization methods is a related concern the authors raise implicitly through their cross-study comparisons. Because different laboratories measure network density, interfacial coverage, and release kinetics with different protocols, pooling results across the plant-based literature is difficult, and design principles risk remaining qualitative. The review’s contribution is to organize the existing evidence into a structure-digestion framework, connecting specific formulation levers to specific digestive outcomes so that future studies can test hypotheses rather than rediscover patterns. Whether the community adopts shared benchmarks will determine how quickly the field can move from descriptive case studies to predictive design.

If those constraints are addressed, the authors argue, plant-based bigels could be systematically positioned for commercial deployment in functional foods, nutraceuticals, and pharmaceutical applications within the next decade. The vision is a new generation of plant-based products in which texture, nutrition, and delivery timing are designed together: a vegan cheese that releases vitamin B12 only in the intestine, a spread that protects polyphenols through the stomach, or a nutraceutical matrix that co-delivers fat-soluble and water-soluble actives on independent schedules. For a field long dominated by single-phase emulsions and hydrogels, the bigel’s two-network logic offers something rare in food science, a structural attribute that doubles as a control system, letting designers write the digestive itinerary of a nutrient before the food ever leaves the factory.

Subject of Research: Structural design and digestive behavior of plant-based bigels for controlled nutrient delivery

Article Title: Designing plant-based bigels for controlled nutrient delivery: structural and digestive perspectives

Article References: Shetty, P., Paulin Patricia, P., Sushmithasri, R., & Rawson, A. (2026). Designing plant-based bigels for controlled nutrient delivery: structural and digestive perspectives. Frontiers in Soft Matter, 6, Article 1888400. https://doi.org/10.3389/frsfm.2026.1888400

Image Credits: AI Generated

DOI: 10.3389/frsfm.2026.1888400

Keywords: food science, bigels, controlled release, nutrient delivery, soft matter, plant-based, gastrointestinal digestion, oleogel, hydrogel, functional foods, Designing, controlled