Structure–Function Relationships of Bigels as Animal Fat Replacers: Phase Inversion‐Induced Structural Diversity and Corresponding Food Application Potential

ABSTRACT

Animal fat–based triacylglycerols contribute unique texture to foods, but their excessive intake poses health risks. Therefore, developing fat replacers that can mimic the plasticity and melting properties of animal triacylglycerols has emerged as a key challenge in soft matter research. In this context, bigels are promising fat replacers due to their comparable thermal and rheological properties. However, they undergo phase inversion modulated by the oil‐to‐water ratio and gelator concentration/type, which determines their final microstructure, namely oil‐in‐water (O/W), bi‐continuous, and water‐in‐oil (W/O). Clarifying the structure–function relationship is critical for designing bigels as animal fat replacers. This review presents the formation of bigels, while also indicating the factors that control their phase inversion. Moreover, the physicochemical properties, long‐term stability, and in vitro digestion behavior of phase inversion–induced bigels are compared, and current applications of these bigels are presented. Finally, this review summarizes promising research directions for developing bigels as advanced fat replacers. The key conclusions are as follows. First, hydrogelator assembly is driven by intermolecular interactions (e.g., hydrogen bonding and hydrophobic association). The structure and mechanical strength are determined by oleogelator crystallization and 3D network formation. The interface between the two phases is stabilized by emulsifiers. Second, with phase inversion induced by the oil‐to‐water ratio, W/O systems exhibit enhanced mechanical properties and low free fatty acid release, while O/W systems exhibit superior oxidative and freeze–thaw stability. Finally, W/O systems are predicted to be suitable for meat products, O/W systems for bakery products, and bi‐continuous systems for 3D‐printed foods.

1. Introduction

Animal fats in foods serve dual functions: they provide nutrition and energy to the human body, and they also influence the texture and sensory characteristics of foods. However, excessive consumption of animal fats poses health risks due to their high saturated fatty acid content, potentially contributing to obesity and cardiovascular diseases (Q. Lin et al. ²⁰²⁴). Consequently, reducing animal fat content in foods aligns with growing consumer demand for healthier dietary options. Currently, two main strategies have been developed to reduce animal fats in foods: directly reducing their content and replacing them with fat replacers. Direct reduction of animal fats in foods can negatively impact the physicochemical characteristics and sensory qualities, potentially leading to reduced consumer acceptability (Gao et al. 2024). Fat replacers are substances that can partially or completely mimic the functions and sensory characteristics of natural fats (Zhu et al. 2025). Their core functionality lies in two areas: mimicking the properties of conventional fats and providing enhanced health benefits (He et al. 2026).

Vegetable oils are promising candidates for fat replacers, as they are richer in monounsaturated and polyunsaturated fatty acids than animal fats, thus exhibiting superior nutritional value (J. Guo, Cui, et al. ²⁰²³). However, because saturated fats remain in a solid state at room temperature, simply replacing them with unsaturated fats can compromise the quality of the final foods (Cho et al. 2023; Rogers ²⁰⁰⁹). To overcome this limitation, vegetable oil crystallization can be modulated to form three‐dimensional (3D) gel networks.

Early research primarily focused on fundamental properties of fat replacers (e.g., texture, rheological properties, microstructure, and quality characteristics). Building upon these foundational studies, recent research has increasingly focused on fat‐structured systems, notably emulsion gels, oleogels, and bigels, aiming to develop optimized fat replacers with tunable characteristics. However, emulsion gels exhibit deficiencies in rigidity, viscoelasticity, and plasticity (Cen et al. 2024) and oleogels, comprising about 90% oil by weight, may contribute to high dietary fat intake (Ghiasi and Golmakani 2022). Therefore, bigels, biphasic gel systems that combine hydrogel and oleogel components (Sinha et al. 2024), have emerged as a promising alternative as fat replacers and gained considerable scientific interest.

In bigels, the hydrogel phase is formed through the cross‐linking of biopolymer chains, which can be accomplished through chemical cross‐linking (covalent bonds), physical cross‐linking (noncovalent interactions), or a combination of both (M. Sun, Wang, et al. ²⁰²⁵). The oleogel phase is a semi‐solid mixture produced by dispersing gelators in oils, resulting in a 3D network that entraps the liquid organic phase (M. Sun, Wang, et al. ²⁰²⁵). This network is mainly stabilized by noncovalent interactions such as hydrogen bonding, van der Waals forces, and hydrophobic interactions (Coelho et al. 2026). Bigels are formed by combining hydrogels and oleogels, integrating the advantageous properties of both components. They can prevent liquid droplets from escaping the 3D gel network, and provide a stable structure without aggregation or flocculation, thereby exhibiting similar thermal, rheological, and structural characteristics to animal fats, with potential as their replacement (C. Li, Xu, et al. ²⁰²⁴). However, bigels may undergo phase inversion depending on the oil‐to‐water ratio and gelator concentration/type, leading to the formation of three different systems: hydrogel‐in‐oleogel (i.e., water‐in‐oil, W/O), bi‐continuous, or oleogel‐in‐hydrogel (i.e., oil‐in‐water, O/W). Therefore, further clarifying the potential of different bigel systems as animal fat replacers is of great significance for promoting their application in low‐fat, conventional‐fat, and high‐fat foods.

This review summarizes the formation of bigels, the factors influencing their phase inversion, and the methods used for their observation. Furthermore, the functional properties of different bigel systems induced by phase inversion are compared. Accordingly, a minimal set of quantifiable and comparable metrics has been identified to characterize their functionality as fat replacers. For evaluating physicochemical properties and long‐term stability, key metrics include texture profile analysis (TPA), apparent viscosity, storage modulus (G′), loss modulus (G″), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), temperature‐dependent G′ and G″, peroxide value (POV), thiobarbituric acid reactive substances (TBARS), and solvent holding capacity. For health‐related functionality, in vitro digestion behavior characterized by free fatty acid release is employed for evaluation. Finally, the applications of different bigel systems in foods are presented and analyzed, which contributes to further clarifying the structure–function relationship of bigels as animal fat replacers.

2. Formation of Bigels

“Soft matter” refers to a class of food materials dominated by weak reversible molecular interactions, exhibiting complex rheological and structural characteristics (Pawde and Dave 2025). Within this framework, bigels, a dual‐network system comprising a hydrogel and an oleogel, are typical representatives of soft matter. During preparation, the aqueous and oil phases form single‐phase gel networks separately and the resulting biphasic mixture is then homogenized to form a stable system. Notably, this biphasic formulation is kinetically stable and fully integrated at the physical level, which qualifies as authentic bigels rather than composite materials linked by covalent chemical bonds. Fourier‐transform infrared (FTIR) spectroscopy can effectively characterize intermolecular interactions and phase compatibility of bigels. The observed characteristic peaks in FTIR spectroscopy corresponding to both the hydrogel and oleogel components confirm the biphasic structure of the bigels, while the absence of new peaks or significant shifts demonstrates no new covalent interactions, indicating that the two phases are physically integrated through hydrogen bonds, van der Waals forces, and hydrophobic interactions, with each retaining its intrinsic structure (Ebrahimi et al. 2026). Building on this structural evidence, comprehensive analysis of individual gelation processes and their synergistic interactions allows for a systematic understanding of bigel formation, which provides a theoretical basis for exploring their structural and functional properties.

2.1. Independent Formation of Pre‐Gel Systems

2.1.1. Formation of Hydrogels

Hydrogels are key 3D network structures for constructing bigels, which are mainly composed of hydrogelators (polysaccharides and proteins) and water. Therefore, the structural characteristics of polysaccharides and proteins directly regulate the microstructure and macroscopic properties of bigels.

The polysaccharides currently applied in food‐grade hydrogels include sodium alginate (Nutter et al. 2023), κ‐carrageenan (M. Zhou et al. ²⁰²⁴), and konjac glucomannan (L. Liu et al. ²⁰²³). Polysaccharides are naturally occurring polymers with excellent stabilizing ability, hydrophilicity, and biodegradability (Cen et al. 2024). Polysaccharide gelation relies on hydrogen bonding, ionic cross‐linking, molecular entanglement, and their synergistic effects (Zhu et al. 2025), among which hydrogen bonding acts as the dominant interaction. The role of polysaccharides in hydrogel formation is schematized in Figure 1A. Their functional properties as fat replacers are related to water‐holding capacity and network density. First, water‐holding capacity is attributed to the formation of hydrogen bonds between water molecules and functional groups (e.g., hydroxyl, carboxyl, and aldehyde groups) on polysaccharide molecules, which promotes the immobilization of free water on polysaccharide chains and enhances water retention (Udo et al. 2023). Second, the interaction between water molecules and other hydrogelators leads to the formation of ordered structures around polysaccharide molecules during the formation of polysaccharide‐based hydrogels, which is conducive to stabilizing the structure (Chao, Li, et al. ²⁰²⁴).

FIGURE 1.

Formation of bigels containing formation of hydrogels (A), formation of oleogels (B), and interactions between components in bigels (C).

The proteins currently used in food‐grade hydrogels are mostly gelatin (Xie et al. 2023), pea protein (Y. Yang et al. ²⁰²⁴), and whey protein isolate (L. Liu, Wang, et al. ²⁰²⁴). The role of proteins in hydrogel formation is schematized in Figure 1A. Their functional properties as fat replacers are related to texture and physicochemical properties. As a component for constructing hydrogels, proteins undergo self‐assembly mainly driven by the synergistic effects of various noncovalent interactions, namely van der Waals forces, hydrogen bonding, hydrophobic interactions, and electrostatic interactions (Gonçalves et al. 2024). Such self‐assembly behavior is usually triggered by specific environmental stimuli, among which temperature is one of the most common and effective regulatory strategies. Taking gelatin as a typical hydrogel example, the polypeptide chains of gelatin molecules exhibit a disordered random coil conformation under conditions above the solidification temperature; however, partial areas reform a triple‐helix structure when the temperature drops below the freezing point (Qiao et al. 2021). This temperature‐induced coil‐to‐helix transition is not only a rearrangement of molecular conformation but also the core mechanism by which proteins drive self‐assembly through non‐covalent interactions and further construct three‐dimensional networks.

Some polysaccharide‐protein combinations currently used in bigels include carboxymethyl cellulose and pea protein (Y. Yang et al. ²⁰²⁴), κ‐carrageenan and gelatin (Zampouni et al. 2024), as well as konjac glucomannan and gelatin (L. Liu et al. ²⁰²³), which are employed to improve texture, stability, and quality of food colloidal systems (J. Guo, Cui, et al. ²⁰²³). Such cooperative interactions between polysaccharides and proteins, facilitated through physical and chemical mechanisms, combine excellent water‐holding and thickening properties of polysaccharides with the relatively superior hydrophobicity and emulsifying properties of proteins (Xu et al. 2024). Therefore, when polysaccharides and proteins coexist in hydrogels, they achieve functional complementarity through intermolecular interactions and jointly construct the three‐dimensional network structure of hydrogels, which is essential for mimicking the structural and functional properties required for fat replacers.

2.1.2. Formation of Oleogels

The 3D crystalline network constructed by oleogelators acts as a critical scaffold for immobilizing liquid oil, which is mainly stabilized by noncovalent interactions such as hydrogen bonding, van der Waals forces, and hydrophobic interactions (Coelho et al. 2026). This crystalline network plays a decisive role in regulating the phase continuity of oleogels by inhibiting oil separation, thereby determining their structural stability and functional properties. Different oleogelators exhibit distinctive crystal morphologies, such as needle‐like and platelet‐like crystals (Figure 1B). During crystallization, needle‐like crystals exhibit a larger surface area, which promotes the contact between microstructural elements, thus facilitating efficient oil entrapment and maintaining a stable oil‐continuous phase (Blake et al. 2014; R. Qiu et al. ²⁰²²). In comparison, platelet‐like crystals can form a stable network even at low oleogelator concentrations (Holey et al. 2021), which serves to stabilize the oil‐continuous phase and enhance structural integrity at the interface. Therefore, the crystallization behavior and crystal morphology of oleogelators determine the microstructure and interfacial stability, thereby governing the phase continuity and stability of oleogels.

2.2. Interactions Between Components in Bigels

2.2.1. Molecular Interactions Between Hydrogels and Oleogels

Concerning molecular interactions (e.g., hydrogen bonding, hydrophobic interactions, and crystal–network entrapment), it is difficult from the existing literature to identify a universally dominant interaction across different systems, as their relative contributions are highly dependent on system composition and external conditions. Instead, these interactions operate synergistically rather than individually to stabilize the structure and determine the final properties. In bigels with interpenetrating hydrogel and oleogel networks, these synergistic interactions are collectively governed by polysaccharides, proteins, and oleogel‐based components, as schematized in Figure 1C.

Polysaccharides can promote hydrogen bonding formation, ionic cross‐linking, and molecular entanglement during the complexation of hydrogels and oleogels, thereby effectively improving the stability of bigels (Q. Jiang, Chen, et al. ²⁰²⁴; Zhu et al. ²⁰²⁵). Proteins play a dual role in stabilizing bigel systems. First, they adsorb at the oil–water interface, reducing interfacial tension, which is essential for stabilizing oleogel droplets. Hydrophobic amino acid residues in proteins can interact with oleogelators and the oil phase via hydrophobic interactions (Cho et al. 2023), while the hydrophobic crystalline network formed by oleogelators immobilizes free water through spatial confinement effects. Therefore, they improve water/oil retention and inhibit phase separation, thus contributing to the overall stability of bigels. Second, the temperature‐dependent triple helix restoration of proteins such as gelatin enables physical entanglement with crystal network of oleogels (Gao et al. 2026). This entanglement, involving the intertwining of helical protein domains with crystals, creates an interpenetrating network that reinforces the interfacial structural barrier and enhances stability. Therefore, multi‐component synergistic interactions effectively regulate the structural and functional properties of bigels.

2.2.2. Interfacial Interactions Mediated by Emulsifiers

The interfacial interactions between hydrogels and oleogels are critical for constructing stable bigels. Emulsifiers are amphiphilic, meaning they possess both hydrophilic and hydrophobic groups (Q. Lin et al. ²⁰²⁴), which can effectively stabilize the interface between the two phases and improve the stability of the bigels. The role of emulsifiers in promoting interactions between hydrogels and oleogels is schematized in Figure 1C. First, emulsifiers can adsorb rapidly at the oil–water interface and form a dense, viscoelastic interfacial layer that effectively prevents coalescence and phase separation, thus improving the stability of systems (Chao, Li, et al. ²⁰²⁴; Y. Liu, Wu, et al. ²⁰²⁴). Second, emulsifiers can self‐assemble into ordered micellar structures or form stable oil/water mixtures, which further regulate interfacial tension and enhance the interfacial compatibility between the two immiscible phases (Cen et al. 2024).

2.3. From Formation to Predictive Functional Performance

Building on a comprehensive understanding of their formation, the functional performance of bigels can be systematically predicted and tailored. Specifically, the key properties of hydrogelators (polysaccharides and proteins) and oleogelators that govern bigel performance are as follows. For polysaccharides, their type, concentration, and hydrophilic group density enable the targeted optimization of water‐holding capacity, lubrication properties, and network density of foods. For proteins, their type, concentration, and thermal induction condition allow precise modulation of the gelation temperature, viscoelastic behavior, and gel strength, thereby achieving a texture distinct from that of the polysaccharide‐based bigels. For oleogelators, the critical properties include crystal morphology, network compactness, hardness, smearability, and oil‐holding capacity. These properties can be precisely controlled by their type, concentration, and crystallization condition to meet the specific texture requirements of foods.

Therefore, by regulating interactions among hydrogelators, oleogelators, and emulsifiers, bigels can be endowed with favorable water‐ and oil‐holding capacities, viscoelasticity, gel strength, texture, and lubrication behavior. These characteristics enable bigels to closely mimic the physicochemical and sensory properties of natural fats.

3. Factors Controlling Phase Inversion

Two‐phase networks of bigels are synergistically constructed by proteins, polysaccharides, oils, oleogelators, and emulsifiers. Nevertheless, such systems are highly susceptible to key factors including the oil‐to‐water ratio, as well as the concentration and type of gelators. These factors can trigger the interconversion between continuous and dispersed phases, a phenomenon defined as phase inversion. Phase inversion gives rise to different bigel systems, and the significant functional differences among these systems directly determine their application potential as animal fat replacers. Therefore, a comprehensive analysis of the key factors and underlying regulatory mechanisms governing phase inversion is essential to clarify the structure–function relationship of bigels.

3.1. Oil‐to‐Water Ratio

In the interpenetrating network structure synergistically constructed by the oil and aqueous phases, phase inversion of bigels can be directly triggered by variations in the oil‐to‐water ratio, with their macroscopic properties modulated accordingly. Therefore, the regulatory mechanism of the oil‐to‐water ratio on phase inversion should be systematically analyzed to facilitate the effective application of bigels as fat replacers.

As schematized in Figure 2A, the oil‐to‐water ratio serves as a decisive factor governing phase inversion of bigels. At low oleogel concentration (< 40%), strong interactions are formed within the hydrogels owing to their high concentration, which prevents interactions within the oil phase, thereby hindering the formation of continuous oleogel networks (Bollom et al. 2020). When the oleogel concentration ranges from 40% to 70%, the hydrogel and oleogel phases reach a relatively balanced ratio. Under this condition, most of the possible interaction sites between the hydrogel and oleogel droplets are saturated, thus promoting the coalescence of oil droplets (Cho et al. 2023). The aggregation of the oleogel phase initially disrupts the hydrogel matrix, generating irregular and discontinuous gel structures (Tian et al. 2024). Subsequently, oil droplets coalesce and fuse into a continuous oleogel phase, where hydrophobic segments are located in the organic phase and polar segments are located in the aqueous phase, ultimately leading to the formation of bi‐continuous systems (Bollom, Clark, and Acevedo ²⁰²⁰). When the concentration of oleogel is increased further (> 70%), the aqueous phase changes from a continuous state to a spherical droplet state, and the oil droplets coalesce to form a large interconnected oil phase, forming W/O systems (Bruno et al. 2024; Pang et al. ²⁰²⁴).

FIGURE 2.

Factors controlling phase inversion containing oil–water ratio (A), gelator concentration (B), and gelator type (C). The images are referenced from published studies (Chen et al. 2025; Giannakaki et al. ²⁰²⁵; Guo et al. ²⁰²⁴; Ham et al. ²⁰²⁵; L. Han et al. ²⁰²⁵; Hashemi, Varidi, and Jafari ²⁰²³; Lee et al. ²⁰²⁴; Z. Liu et al. ²⁰²⁵; Xue et al. ²⁰²⁴; Zampouni et al. ²⁰²³; Zhao, Rao, and Chen ²⁰²⁶). The list includes only references not cited in the main text.

In conclusion, the oil‐to‐water ratio is not merely a compositional variable but a driver of phase inversion in bigel systems. By increasing the oleogel concentration, bigels predictably transition through three distinct systems: O/W systems at low concentration (< 40%), bi‐continuous systems at a balanced ratio, and inverted W/O systems at high concentration (> 70%). This clear, ratio‐dependent phase behavior provides a foundational framework for tailoring bigel microstructure to achieve desired textural and functional performance in various applications. It should be emphasized that the aforementioned oleogel fraction ranges (< 40%, 40%–70%, and > 70%) are general classifications summarized from published literature observations, rather than universal fixed critical thresholds applicable to all bigels. These phase inversion thresholds can shift substantially when altering the concentration and type of gelators (Fasolin et al. 2021; Su et al. ²⁰²⁴; Y. Yang et al. ²⁰²⁴), concentration and type of emulsifier (Mao and Meng 2024; Xie et al. ²⁰²³), as well as processing conditions (Fasolin et al. 2021; L. Liu et al. ²⁰²³).

3.2. Concentration and Type of Gelators

Gelators, including hydrogelators and oleogelators, serve as the structural pillars of bigel systems by stabilizing the aqueous and oil phases into semi‐solid networks, enabling their long‐term coexistence. Considering their role in governing network formation, it is crucial to elucidate the intrinsic relationship between gelators and the phase inversion behavior of bigels.

As schematized in Figure 2B,C, relevant studies indicate that phase inversion in bigels does not depend on either the gelator concentration or gelator type. Instead, phase inversion is primarily governed by the oil‐water ratio, occurring exclusively within a relatively narrow balanced range.

A plausible interpretation is that the oil‐to‐water ratio is the main parameter regulating phase inversion. At relatively balanced oil–water ratios, variations in the type and concentration of hydrogelators or oleogelators may give rise to O/W, W/O, or bi‐continuous systems. However, at low concentration (< 40%), bigels mainly form O/W systems, whereas at high concentration (> 70%), they tend to form W/O systems.

3.3. Dominant Factors Governing Phase Inversion

Among the various factors governing phase inversion, the oil‐to‐water ratio is widely recognized as the dominant driver, exhibiting a causal relationship with phase inversion behavior. In contrast, factors such as the concentration and type of gelators show only a correlative relationship, playing a secondary modulating role. Therefore, given the complexity arising from multifactorial synergistic effects, this review focuses on the oil‐to‐water ratio as the core variable, comparing different bigel systems induced by this parameter and systematically evaluating their functional performance as animal fat replacers.

4. Determination of Phase Inversion in Bigels

Previous section has systematically summarized the regulatory mechanisms underlying phase inversion in bigels, emphasizing the critical roles of formulation in directing their microstructural evolution. However, elucidating the above mechanisms relies critically on the accurate identification and characterization of phase inversion behavior. For this purpose, microscopes, 3D models, and low‐field nuclear magnetic resonance images (MRI) enable direct visualization of the aqueous and oil phase distributions. Corresponding images depicting the phase inversion of bigels are schematized in Figure 3.

FIGURE 3.

Determination of phase inversion in bigels containing optical microscope images (A), scanning electron microscopy images (B), polarized light microscopy images (C), confocal laser microscopy images (D), construction of 3D models (E), and magnetic resonance images (F). The images are referenced from published studies (J. Guo, Gu, et al. ²⁰²³; Q. Jiang, Chen, et al. ²⁰²⁴; Pang et al. ²⁰²⁴; M. Sun, Wang, et al. ²⁰²⁵; R. Zheng et al. ²⁰²³; M. Zhou, Li, et al. ²⁰²⁵). All images are reprinted with permission from Elsevier.

4.1. Microscope Imaging

4.1.1. Optical Microscope Imaging

Optical microscopes can distinguish between the aqueous and oil phases based on their colors (Figure 3A). Kaimal and Singhal (2023) observed that the oil phase appeared yellow while the aqueous phase appeared transparent in bright‐field optical microscope images, allowing identification of bigel types based on color distribution. H. Zheng et al. (2020) stained the oil phase with Sudan I, where the red regions indicated the oil phase, enabling the microstructure of bigels to be identified based on oil phase distribution.

Optical microscopy facilitates direct observation of phase morphology and droplet distribution in bigels, but has notable limitations. This method only provides two‐dimensional (2D) information on the surface microstructure and cannot obtain internal three‐dimensional details. Meanwhile, its limited resolution makes it difficult to clearly distinguish extremely small droplets and delicate interfacial structures. Furthermore, staining agents may alter the interfacial interactions and contact angle between the oil and aqueous phases, and this technique cannot be used for the quantitative analysis of key parameters such as phase distribution and interfacial strength.

4.1.2. Scanning Electron Microscopy Imaging

Scanning electron microscopy (SEM) enables the identification of O/W or W/O systems by observing the properties of the oil–water interface and the encapsulation of the oil phase within the aqueous phase (Figure 3B). Based on SEM observations, Q. Jiang, Chen, et al. (2024) concluded that oleogel droplets were embedded in a dense honeycomb‐shaped hydrogel network in O/W systems, that bi‐continuous systems could be identified by the partial dispersion and continuity of the oleogel droplets, and that W/O systems were identified by the continuous smooth oil phase and the embedded honeycomb hydrogel network.

SEM can clearly reveal the micromorphology and interface structure of bigels, but also has obvious limitations. This technology requires sample pre‐treatment such as drying and gold spraying, which can easily damage the original wet state and internal structure. Moreover, it only reveals surface morphology rather than the internal 3D phase distribution, and cannot clearly distinguish between the oil and aqueous phases. Furthermore, it allows neither dynamic observation nor quantitative characterization of interfacial properties and phase behavior.

4.1.3. Polarized Light Microscopy Imaging

Polarized light microscopy (PLM) enables the identification of whether the oil phase is dispersed or continuous based on the distribution and morphology of crystals (Figure 3C). Z. Chen, Bian, et al. (2023) found that transparent crystals appeared in the regions where the droplets were located, indicating the formation of O/W systems; conversely, the presence of crystals in the continuous phase suggested the formation of W/O systems.

Although PLM enables effective observation of crystalline structures in bigels, it presents notable limitations. It can only detect crystalline regions, whereas amorphous phases cannot be visualized. In addition, PLM cannot clearly distinguish the oil phase, aqueous phase, and gel network in bigels, nor can it provide quantitative information on phase distribution. Furthermore, the observation results are easily influenced by sample thickness and light intensity, making it difficult to achieve accurate and reproducible characterization.

4.1.4. Confocal Laser Microscopy Imaging

Confocal laser scanning microscopy (CLSM) is a powerful tool to characterize the interaction between aqueous and oil phases in bigels. CLSM eliminates any information outside of the focal plane by using a spatial pinhole in front of the detector to focus light at a specific depth, enabling high‐resolution imaging (H. Q. Li and Wan ¹⁹⁹⁵). CLSM can also be operated in fluorescence mode by using a different laser light source with a shorter wavelength, where the molecules absorb high‐energy light and emit low‐energy light after a short relaxation period (Pipintakos et al. 2021). Different fluorescent probes can distinguish internal, external, and various crystalline phases (Teo et al. 1998). Selective staining of oleogels and hydrogels in bigels facilitates better characterization of the interactions between the aqueous and oil phases (Figure 3D). In reported studies, the aqueous phase is generally stained with a fluorescent probe that emits blue/green fluorescence, while the oil phase is stained with a probe that emits red fluorescence. Under these specific staining conditions, O/W systems are formed when red particles are distributed within a continuous blue or green aqueous phase (Bollom et al. 2020). An interpenetrating network structure with no obvious difference between the dispersed and continuous phases, indicated by red and blue or green regions, respectively, implies the formation of bi‐continuous systems (Chao, Yan, et al. ²⁰²⁴). When blue or green spherical droplets appear in a red continuous phase of bigels, this indicates the formation of W/O systems (Q. Jiang, Chen, et al. ²⁰²⁴). Therefore, the interactions between aqueous and oil phases can be understood by analyzing the color distribution in CLSM images, thereby distinguishing the types of bigels.

Although CLSM can distinguish between aqueous and oil phases, it still has certain limitations. Fluorescent dyes may interfere with the native structure of the sample. In particular, fluorescent staining may modify the interfacial properties and alter the contact angle between the two phases. Furthermore, high‐energy laser irradiation may cause local heating and induce melting of wax crystals in the oleogel phase, thus disrupting the native crystalline network. In addition, this technique is not readily applicable for real‐time dynamic observation.

4.2. Construction of 3D Models

The optical slicing function of CLSM can be used to generate planar vertical or horizontal slices if the sample has sufficient transparency to allow for deep imaging. These slices can then be reconstructed into a 3D image of the component distribution by using software (Pygall et al. 2007). First, CLSM can obtain multiple 2D images by moving the laser‐focused focal plane (i.e., x–y plane) through the sample depth along the z‐axis at specified thickness steps (Mhaske et al. 2019). A 3D model can then be obtained from the fluorescence overlay images using Zen Blue software (Zeiss, Germany) (Q. Jiang et al. ²⁰²²), which can further determine the critical points and specific processes of phase inversion (Figure 3E). J. Guo, Gu, et al. (2023) observed that distinct O/W systems were formed when the oleogel concentration was 54 wt%, that the distribution of the aqueous phase gradually split from a continuous state into large regions when the oleogel concentration was increased to 56 wt%, and that typical W/O systems appeared when the oleogel concentration was further increased to 60 wt%. In summary, the construction of a 3D model can visualize the types of bigels more clearly and accurately compared to CLSM images, while also determining the threshold of phase inversion.

Despite the ability of CLSM to reconstruct 3D models of bigels, this approach still has several limitations. The 3D reconstruction is highly dependent on image quality and is easily affected by fluorescence noise and light scattering. In addition, the reconstruction process is time‐consuming and requires complex software processing. Most importantly, the acquired 3D model only captures partial structural information instead of the full internal phase distribution, which can be mainly attributed to two inherent technical defects of this characterization method. First, the laser penetration depth is limited, leading to severe signal attenuation in deep regions of thick samples. Second, images only visualize the fluorescently labeled phase, while the unlabeled regions remain undetectable.

4.3. Low‐Field Nuclear Magnetic Resonance

MRI enables quantitative and qualitative analysis by measuring T ₁ and T ₂ relaxation times (longitudinal and transverse relaxation), which are closely related to water content and water distribution, together with chemical shift, proton density, and 2D/3D spatial distribution (Ozel and Oztop 2021). Low‐field MRI revealed the relative distribution of aqueous and oil phases in bigels (W. Liu, He, et al. ²⁰²⁴; Marcone et al. ²⁰¹³). In Figure 3F, the color intensity corresponds to the level of hydrogen protons, and strong signals (represented in red) indicate a high density of hydrogen protons (Xie et al. 2023). Habibi et al. (2022) and M. Sun, Wang, et al. (2025) revealed that the continuity and distribution of the oil phase changed as systems transitioned from O/W to W/O. First, the red regions were encapsulated by the aqueous phase in O/W systems; second, the red regions expanded into the major continuous phase, indicating that the system transformed into W/O systems.

Beyond imaging, T ₂ relaxation time distribution analysis provides a non‐destructive tool for probing the distribution of water and oil in bigels. Water molecules in different states, such as bound water and free water, exhibit distinct T ₂ relaxation times due to differences in molecular mobility. Parameters A ₂₁, A ₂₂, and A ₂₃ correspond to the relative percentages of bound water, immobilized water, and free water relative to the total water content, respectively (Teng et al. 2026). Q. Jiang, Chen, et al. (2024) reported that the transverse relaxation time of W/O systems shifted toward lower values, accompanied by a significant increase in the peak area of A ₂₂. According to Teng et al. (2026), W/O systems exhibited a higher A ₂₂ value, whereas O/W systems showed a higher A ₂₃ value, which may indirectly reflect the occurrence of phase inversion.

MRI can visualize phase inversion of bigels, but it still has obvious limitations. The resolution of MRI is relatively low, making it difficult to observe fine microstructures and interfacial details. The imaging speed is slow, which is not conducive to real‐time monitoring of phase inversion processes. In addition, the instrument is sensitive to environmental factors such as temperature and magnetic field stability. Monitoring the evolution of T ₂ relaxation time distributions enables indirect identification of phase inversion points. However, this method lacks spatial resolution and provides only indirect structural information.

4.4. Comparative Evaluation and Combined Application of Different Techniques

Different techniques exhibit distinct advantages and limitations in observing phase inversion in bigels. A comprehensive comparison is critical for selecting appropriate analytical tools. Overall, the above techniques complement one another in observing phase inversion in bigels. Optical microscopy and PLM are suitable for preliminary observation. SEM provides morphological imaging. CLSM exhibits unique advantages in 3D structural observation. MRI and T ₂ relaxation time distribution analysis offer non‐destructive detection of phase behavior. In practical applications, a combination of multiple methods is required to comprehensively and accurately elucidate the phase inversion mechanism and microstructural evolution of bigels.

5. Functional Properties of Different Bigel Systems Induced by Phase Inversion

After clarifying the key influencing factors and determination methods governing the phase inversion of bigels, further comparison of the physicochemical properties, long‐term stability, and in vitro digestion behavior of different bigel systems is conducive to revealing the intrinsic structure–function relationship, thereby enabling the prediction and evaluation of their application potential as food fat replacers.

5.1. Physicochemical Properties

5.1.1. Appearance

As the fundamental and common indicator for evaluating the stability of bigels, appearance has the prominent advantages of simple operation and intuitive observation. Visual observation can be directly observed to quickly and accurately verify whether the prepared bigels have achieved the desired state.

From the complementary information of Table 1, it can be seen that different bigel systems showed no appearance deterioration (e.g., stratification, abnormal color). The samples presented a uniform and intact gel morphology, indicating satisfactory visual appearance for bigels. This favorable appearance can be attributed to the interactions between their internal 3D hydrogel networks and crystalline oleogel structures (Figure 1). These interactions may prevent phase separation and morphological collapse, enabling the well‐maintained appearance of bigels. However, such visual observations alone are insufficient for a comprehensive evaluation. A series of quantitative characterizations including TPA, rheology, and thermodynamic properties are provided in the following sections.

TABLE 1.

Physicochemical properties and in vitro digestion behavior of different bigel systems induced by phase inversion.

Physicochemical properties and in vitro digestion behavior		Optimal system	Different bigel systems	Key formulation parameters	Performance	References
Appearance		All	W/O Bi‐continuous O/W	Hydrogel: Whey protein (15%, w/w) Oleogel: Soy lecithin: Stearic acid = 7:3 (20%, w/w) Soybean oil	● Stable	Bollom et al. (2020)
		All	W/O Bi‐continuous O/W	Hydrogel: Myofibrillar protein (40 mg/mL) Oleogel: Beeswax (10%, w/v) Corn germ oil	● Stable	L. Zhang et al. (2025a)
		All	W/O Bi‐continuous O/W	Hydrogel: Powdered grass pea protein isolate (12%, w/w) Oleogel: Carnauba wax (7% and 9%, w/w) Sesame oil	● Stable	Lotfi Shirazi and Koocheki (2025)
		All	W/O Bi‐continuous O/W	Hydrogel: Cellulose nanofibers (2.0, w/w) Oleogel: Beeswax (8.0%, w/w) Soybean oil	● Stable	Z. Liu, Hu, et al. (2025)
		All	W/O Bi‐continuous O/W	Hydrogel: κ‐carrageenan (2%, w/w) Starch (0% or 10%, w/w) Oleogel: Beeswax (20%, w/w) Soybean oil	● Stable	M. Zhou et al. (2024)
		All	W/O Bi‐continuous O/W	Hydrogel: Myofibrillar proteins (40 mg/mL) Oleogel: Glycerin monostearate Corn germ oil	● Stable	L. Zhang et al. (2025b)
		All	W/O Bi‐continuous	Hydrogel: Agar (5%) Xanthan gum (1%) Oleogel: Beeswax (15%) Soy lecithin (2%) Sunflower oil	● Stable	Ramos‐Souza et al. (2025)
		All	W/O Bi‐continuous	Hydrogel: Cellulose nanofibers (0.6%, w/w) Oleogel: Glycerol monostearate (10%, w/w) Sunflower seed oil	● Stable	Hou et al. (2024)
		All	W/O O/W	Hydrogel: Xanthan gum (1%, w/w) Agar (5%, w/w) Oleogel: Carnauba wax (15%, w/w) Lecithin (2%, w/w) Sunflower oil	● Stable	Fernandes et al. (2025)
		All	W/O O/W	Hydrogel: Flaxseed gum (1%, w/w) Oleogel: Soy lecithin (1%, w/w) Beeswax (3%, w/w) Soybean oil	● Stable	P. Li, Chen, et al. (2025)
		All	W/O O/W	Hydrogel: Wheat starch (10%, w/w) Oleogel: Ethylcellulose (10%, w/w) Sunflower oil	● Stable	Ghiasi and Golmakani (2022)
		All	W/O O/W	Hydrogel: Agar (2%, w/w) κ‐carrageenan (1%, w/w) Oleogel: Sunflower wax or Sunflower wax:Monoglyceride = 1:1 (10%, w/w) Olive oil	● Stable	Dimakopoulou‐Papazoglou et al. (2025)
		All	Bi‐continuous O/W	Hydrogel: Xanthan gum (1%, w/w) Oleogel: Glycerol monostearate (3% w/w) Lecithin (1%, w/w) Soybean oil	● Stable	Yi et al. (2025)
		All	W/O O/W	Hydrogel: Spirulina platensis protein nanoparticles (1%, w/w) Xanthan gum (1%, w/w) Oleogel: Sunflower wax (5%, w/w) Soybean oil	● Stable	J. Guo, Gu, et al. (2023)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Gelatin:Carboxymethyl chitosan = 1:1, 1:2, 2:1 (4 %, w/w) Oleogel: Beeswax (8%, w/w) Soybean oil	● Stable	L. Li, Feng, et al. (2025)
		W/O	W/O O/W	Hydrogel: Hydroxypropyl methylcellulose (3%) Oleogel: Beeswax (10%) Polyglycerol polyricinoleate (1%) Soybean oil	● Stable	Z. Chen, Bian, et al. (2023)
		Bi‐continuous	Bi‐continuous O/W	Hydrogel: Canola protein (15%, w/w) Oleogel: Candelilla wax (6%, w/w) Canola oil	● Stable	Moguiliansky et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Low acyl gellan gum (0.8%, w/w) or high acyl gellan gum (0.8%, w/w) Oleogel: Glyceryl monolaurate (10%, w/w) Rapeseed oil	● Stable	X. Wang et al. (2024)
Mechanical properties	Texture profile analysis	W/O	W/O Bi‐continuous O/W	Hydrogel: Gelatin (10%, w/w) Oleogel: Lacquer wax:Beeswax = 6:4 (20%, w/w) Camellia oil	● Hardness ↑ ● Springiness ↑ ● Gumminess ↑ ● Chewiness ↑	L. Yang et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Soy protein isolate (6%, w/v) Sugar beet pectin (4%, w/v) Oleogel: Glycerol monostearate (2%, w/w) Beeswax (6%, w/w) Soybean oil	● Hardness ↑ ● Springiness ↑ ● Chewiness ↑	Teng et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Corn silk particles (3%, w/v) κ‐carrageenan (1%, w/w) Oleogel: Candelilla wax (5%, w/w) Flaxseed oil	● Hardness ↑ ● Gumminess ↑	Cai and Lu (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Potato protein (12%, w/v) Carboxymethyl chitosan (1.5% or 3%, w/v) Oleogel: Glycerol monostearate (10%, w/v) Corn oil	● Hardness ↑ ● Chewiness ↑ ● Cohesiveness ↑ ● Gumminess ↑ ● Resilience ↑	X. Zhao, Wang, et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Chlorella pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● Hardness ↑ ● Adhesiveness ↑ ● Chewiness ↑	Q. Jiang, Chen, et al. (2024)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Hydroxypropyl methylcellulose (3%) Oleogel: Beeswax (10%) Polyglycerol polyricinoleate (1%) Soybean oil	● Hardness ↑ ● Gumminess ↑	Z. Chen, Bian, et al. (2023)
		Bi‐continuous	W/O Bi‐continuous O/W	Hydrogel: Gelatin:Carboxymethyl chitosan = 1:1, 1:2, 2:1 (4%, w/w) Oleogel: Beeswax (8%, w/w) Soybean oil	● Cohesiveness ↑	L. Li, Feng, et al. (2025)
		Bi‐continuous	W/O Bi‐continuous O/W	Hydrogel: Spirulina platensis protein nanoparticles (1%, w/w) Xanthan gum (1%, w/w) Oleogel: Sunflower wax (5%, w/w) Soybean oil	● Hardness ↑ ● Springiness ↑ ● Gumminess ↑	J. Guo, Gu, et al. (2023)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Whey protein isolate (2.5 %, w/w) Gelatin (2.5%, w/w) Oleogel: Beeswax:Plant sterol ester = 6:4 (20%, w/w) Diacylglycerol corn oil	● Hardness ↑ ● Cohesiveness ↑ ● Gumminess ↑ ● Chewiness ↑ ● Resilience ↑	Qian et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Gelatin:Carboxymethyl chitosan = 1:1, 1:2, 2:1 (4%, w/w) Oleogel: Beeswax (8%, w/w) Soybean oil	● Hardness ↑ ● Springiness ↑ ● Reilience ↑ ● Chewiness ↑ ● Gumminess ↑	L. Li, Feng, et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Soy protein isolate (6%, w/v) Sugar beet pectin (4%, w/v) Oleogel: Glycerol monostearate (2%, w/w) Beeswax (6%, w/w) Soybean oil	● Cohesiveness ↑	Teng et al. (2026)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Corn silk particles (3%, w/v) κ‐carrageenan (1%, w/w) Oleogel: Candelilla wax (5%, w/w) Flaxseed oil	● Springiness ↑	Cai and Lu (2026)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Potato protein (12%, w/v) Carboxymethyl chitosan (1.5% or 3%, w/v) Oleogel: Glycerol monostearate (10%, w/v) Corn oil	● Springiness ↑	X. Zhao, Wang, et al. (2026)
		O/W	W/O Bi‐continuous O/W	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● Cohesiveness ↑	Q. Jiang, Chen, et al. (2024)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Hydroxypropyl methylcellulose (3%) Oleogel: Beeswax (10%) Polyglycerol polyricinoleate (1%) Soybean oil	● Cohesiveness ↑ ● Springiness ↑	Z. Chen, Bian, et al. (2023)
	Rheology	W/O	W/O Bi‐continuous O/W	Hydrogel: Gelatin (10%, w/w) Oleogel: Lacquer wax:Beeswax = 6:4 (20%, w/w) Camellia oil	● Apparent viscosity ↑ ● Frequency (G′ and G″) ↑	L. Yang et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Soy protein isolate (6%, w/v) Sugar beet pectin (4%, w/v) Oleogel: Beeswax (6%, w/w) Glycerol monostearate (2%, w/w) Soybean oil	● Frequency (G′ and G″) ↑	Teng et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Corn silk particles (3%, w/v) κ‐carrageenan (1%, w/w) Oleogel: Candelilla wax (5%, w/w) Flaxseed oil	● Shear viscosity ↑ ● Frequency (G′ and G″) ↑	Cai and Lu (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Deacetyl chitosan powder (3%, w/w) Oleogel: Beeswax (5%, w/w) Perilla seed oil	● Apparent viscosity ↑ ● Strain (G′ and G″) ↑ ● Angular frequency (G′ and G″) ↑	X. Li et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Potato protein (12%, w/v) Carboxymethyl chitosan (1.5% or 3%, w/v) Oleogel: Glycerol monostearate (10%, w/v) Corn oil	● Strain (G′ and G″) ↑ ● Frequency (G′ and G″) ↑ ● Apparent viscosity ↑	X. Zhao, Wang, et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Gellan gum (1.2%, w/w) Oleogel: Glycerol monostearate (4%, w/w) Palm oil:Algae oil = 1:1	● Apparent viscosity ↑ ● Amplitude (G′ and G″) ↑ ● Frequency (G′ and G″) ↑	Wei et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Myofibrillar protein (40 mg/mL) Oleogel: Beeswax (10%, w/v) Corn germ oil	● Frequency (G′ and G″) ↑	L. Zhang et al. (2025a)
		W/O	W/O Bi‐continuous O/W	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● Frequency (G′ and G″) ↑	Q. Jiang, Chen, et al. (2024)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Gelatin:Carboxymethyl chitosan = 1:1, 1:2, 2:1 (4%, w/w) Oleogel: Beeswax (8%, w/w) Soybean oil	● Viscosity ↑	L. Li, Feng, et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Cellulose nanofibers (2.0, w/w) Oleogel: Beeswax (8.0%, w/w) Soybean oil	● Steady shear viscosity ↑	Z. Liu, Hu, et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Low acyl gellan gum (0.8%, w/w) or High acyl gellan gum (0.8%, w/w) Oleogel: Glycerol monolaurate (10 %, w/w) Rapeseed oil	● Amplitude (G′/G″) ↑ ● Frequency (G′/G″) ↑	X. Wang et al. (2024)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Gelatin (10%, w/w) Oleogel: Glyceryl monostearate (9%, w/w) Fish oil	● Strain (G′ and G″) ↑ ● Frequency (G′ and G″) ↑ ● viscosity ↑	M. Sun, Wang, et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Low acyl gellan gum (2%, w/w) Oleogel: Beeswax (2%, w/w) Algal oil	● Strain (G′ and G″) ↑ ● Frequency (G′ and G″) ↑	Chao et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Xanthan gum (1%, w/w) Oleogel: Stearic acid:Myristic acid = 2:8 (10%, w/w) Sunflower oil	● Amplitude (G′ and G″) ↑ ● Frequency (G′ and G″) ↑	R. Zheng et al. (2023)
		W/O	W/O Bi‐continuous O/W	Hydrogel: κ‐carrageenan (1.5%, w/w) Oleogel: Monoglycerides (20%, w/w) Corn oil	● Frequency (G′) ↑	H. Zheng et al. (2020)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Starch (8%, w/v) Oleogel: Monoglycerides (5%, w/v) Soybean oil	● Apparent viscosity ↑ ● Strain (G′ and G″) ↑ ● Frequency (G′ and G″) ↑	W. Liu, Liu, et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Soy protein isolate (6%, w/v) Sugar beet pectin (4%, w/v) Oleogel: Beeswax (6%, w/w) Glycerol monostearate (2%, w/w) Soybean oil	● Apparent viscosity ↑	Teng et al. (2026)
		O/W	W/O Bi‐continuous O/W	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● Steady shear viscosity ↑	Q. Jiang, Chen, et al. (2024)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Cellulose nanofibers (2.0, w/w) Oleogel: Beeswax (8.0%, w/w) Soybean oil	● Frequency (G′ and G″) ↑	Z. Liu, Hu, et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Low acyl gellan gum (0.8%, w/w) or high acyl gellan gum (0.8%, w/w) Oleogel: Glyceryl monolaurate (10%, w/w) Rapeseed oil	● Apparent viscosity ↑	X. Wang et al. (2024)
Thermodynamic properties	DSC TGA	W/O	W/O Bi‐continuous O/W	Hydrogel: Myofibrillar protein (40 mg/mL) Oleogel: Beeswax (10%, w/v) Corn germ oil	● DSC (T m) ↑	L. Zhang et al. (2025a)
		W/O	W/O O/W	Hydrogel: Powdered grass pea protein isolate (12%, w/w) Oleogel: Carnauba wax (7% and 9%, w/w) Sesame oil	● TGA (mass) ↑	Lotfi Shirazi and Koocheki (2025)
		W/O	W/O O/W	Hydrogel: Flaxseed gum (1%, w/w) Oleogel: Beeswax (3%, w/w) Soy lecithin (1%, w/w) Soybean oil	● DSC (T m) ↑	P. Li, Chen, et al. (2025)
		W/O	W/O O/W	Hydrogel: Agar (2%, w/w) κ‐carrageenan (1%, w/w) Oleogel: Sunflower wax (10%, w/w) or Sunflower wax:Monoglycerides = 1:1 (10%, w/w) Olive oil	● DSC (ΔH) ↑	Dimakopoulou‐Papazoglou et al. (2025)
		W/O	W/O Bi‐continuous	Hydrogel: Cellulose nanofibers (0.6%, w/w) Oleogel: Glycerol monostearate (10%, w/w) Sunflower seed oil	● DSC (ΔH) ↑	Hou et al. (2024)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Xanthan gum (1%, w/w) Oleogel: Stearic acid:Myristic acid = 2:8 (10%, w/w) Sunflower oil	● DSC (T m onset, T m offset, and ΔH) ↑	R. Zheng et al. (2023)
		W/O	W/O Bi‐continuous O/W	Hydrogel: κ‐carrageenan (1.5%, w/w) Oleogel: Monoglycerides (20%, w/w) Corn oil	● DSC (T onset and T peak) ↑	H. Zheng et al. (2020)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Deacetyl chitosan powder (3%, w/w) Oleogel: Beeswax (5%, w/w) Perilla seed oil	● DSC (T on, T peak, and ΔH) ↑	X. Li et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Potato protein (12%, w/v) Carboxymethyl chitosan (1.5% or 3%, w/v) Oleogel: Glycerol monostearate (10%, w/v) Corn oil	● DSC (T m and ΔH) ↑	X. Zhao, Wang, et al. (2026)
		W/O	W/O Bi‐continuous	Hydrogel: Chestnut starch (5%, w/w) Oleogel: Γ‐oryzanol:β‐sitosterol = 3:2 (10%, w/w) High oleic sunflower oil	● DSC (T p and ΔH) ↑	Ma et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● DSC (T m and ΔH) ↑	Q. Jiang, Chen, et al. (2024)
		Bi‐continuous	Bi‐continuous O/W	Hydrogel: Canola protein (15%, w/w) Oleogel: Candelilla wax (6%, w/w) Canola oil	● TGA (weight) ↑	Moguiliansky et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Myofibrillar proteins (40 mg/mL) Oleogel: Glycerin monostearate Corn germ oil	● DSC (T m) ↑	L. Zhang et al. (2025b)
		O/W	W/O Bi‐continuous O/W	Hydrogel: κ‐carrageenan (2%, w/w) Starch (0 or 10%, w/w) Oleogel: Beeswax (20%, w/w) Soybean oil	● DSC (T on and ΔH) ↑	M. Zhou et al. (2024)
	Temperature scanning	W/O	W/O Bi‐continuous O/W	Hydrogel: Gelatin (10%, w/w) Oleogel: Glyceryl monostearate (9%, w/w) Fish oil	● G′ and G″: 10°C–70°C ↑	M. Sun, Wang, et al. (2025)
		Bi‐continuous	W/O Bi‐continuous O/W	Hydrogel: Soy protein isolate (6%, w/v) Sugar beet pectin (4%, w/v) Oleogel: Beeswax (6%, w/w) Glycerol monostearate (2%, w/w) Soybean oil	● G′ and G″: 20°C–40°C W/O ↑ 50°C–80°C Bi‐continuous ↑	Teng et al. (2026)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Myofibrillar protein (40 mg/mL) Oleogel: Beeswax (10%, w/v) Corn germ oil	● G′ and G″: 25°C–45°C W/O ↑ 50°C–80°C O/W ↑	L. Zhang et al. (2025a)
		O/W	W/O Bi‐continuous O/W	Hydrogel: κ‐carrageenan (2%, w/w) Starch (0% or 10%, w/w) Oleogel: Beeswax (20%, w/w) Soybean oil	● G′ and G″: 25°C–80°C ↑	M. Zhou et al. (2024)
		O/W	W/O Bi‐continuous O/W	Hydrogel: κ‐carrageenan (1.5%, w/w) Oleogel: Monoglycerides (20%, w/w) Corn oil	● G′ and G″: 10°C–50°C W/O ↑ 60°C–80°C O/W ↑	H. Zheng et al. (2020)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Gellan gum (1.2%, w/w) Oleogel: Glycerol monostearate (4%, w/w) Palm oil:Algae oil = 1:1	● G′ and G″: 10°C–40°C W/O ↑ 50°C–70°C O/W ↑	Wei et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● G′ and G″: 80°C ↑	Q. Jiang. Chen, et al. (2024)
		O/W	O/W W/O	Hydrogel: Whey protein isolate (11%, w/v) Oleogel: Glycerol monostearate (10%, w/w) Soy lecithin (5%, w/w) Sunflower oil	● G′ and G″: 30°C–90°C ↑	Clímaco et al. (2026)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Low acyl gellan gum (2%, w/w) Oleogel: Beeswax (2%, w/w) Algae oil	● G′ and G″: 25°C–80°C ↑	Chao, Yan, et al. (2024)
		O/W	W/O O/W	Hydrogel: Hydroxypropyl methylcellulose (3%) Oleogel: Beeswax (10%) Polyglycerol polyricinoleate (1%) Soybean oil	● G' and G″: 25°C–50°C W/O ↑ 60°C–80°C O/W ↑	Z. Chen, Bian, et al. (2023)
In vitro digestion behavior		W/O	W/O Bi‐continuous O/W	Hydrogel: Whey protein isolate (2.5%, w/w) Gelatin (2.5%, w/w) Oleogel: Beeswax:Plant sterol ester = 6:4 (20%, w/w) Diacylglycerol corn oil	● Free fatty acid release ↓	Qian et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Deacetyl chitosan powder (3%, w/w) Oleogel: Beeswax (5%, w/w) Perilla seed oil	● Free fatty acid release ↓	X. Li et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Potato protein (12%, w/v) Carboxymethyl chitosan (1.5% or 3%, w/v) Oleogel: Glycerol monostearate (10%, w/v) Corn oil	● Free fatty acid release ↓	X. Zhao, Wang, et al. (2026)
		W/O	W/O Bi‐continuous O/W	Hydrogel: Gellan gum (1.2%, w/w) Oleogel: Glycerol monostearate (4%, w/w) Palm oil:algae oil = 1:1	● Free fatty acid release ↓	Wei et al. (2025)
		W/O	W/O Bi‐continuous O/W	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● Free fatty acid releasee ↓	Q. Jiang, Chen, et al. (2024)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Gelatin:Carboxymethyl chitosan = 1:1, 1:2, 2:1 (4 %, w/w) Oleogel: Beeswax (8%, w/w) Soybean oil	● Free fatty acid release ↓	L. Li, Feng, et al. (2025)
		O/W	W/O Bi‐continuous O/W	Hydrogel: Low acyl gellan gum (2%, w/w) Oleogel: Beeswax (2%, w/w) Algal oil	● Free fatty acid release ↓	Chao et al. (2025)

5.1.2. Mechanical Properties

5.1.2.1. Texture Profile Analysis

Texture analysis simulates the mechanical action of the tongue and teeth, thereby reflecting the sensory attributes of bigels (Y. Yang et al. ²⁰²⁴). TPA parameters, including hardness, springiness, cohesiveness, chewiness, and elasticity, are key textural properties of bigels that are closely related to their chewing behavior (Zampouni et al. 2024).

As summarized in Table 1, the textural properties of bigels were strongly dependent on their structures, with W/O and O/W systems exhibiting distinct mechanical profiles. W/O systems presented higher hardness, gumminess, and chewiness. This can be attributed to two synergistic factors (Figure 4A). At the structural level, the higher concentration of oleogels in the continuous phase provides abundant crystallization sites, facilitating the formation of a more continuous and stronger crystal network (X. Zhao, Wang, et al. ²⁰²⁶). At the molecular level, the increased oleogel concentration strengthens hydrogen‐bonding interactions, which restricts the mobility of the liquid phase and consequently forms a more solid‐like gel matrix (X. Lin, Liu, Ma, Li, and Zheng ²⁰²⁵). In contrast, O/W systems exhibited superior springiness and cohesiveness. Unlike the densely packed crystal network in W/O systems, the gel network in O/W systems avoids excessive densification, which favors efficient elastic recovery after deformation and imparts higher flexibility to the system (M. Sun, Wang, et al. ²⁰²⁵).

FIGURE 4.

Texture profile analysis and rheology (A) and thermodynamic properties (B) of different bigel systems induced by phase inversion.

5.1.2.2. Rheology

Rheology quantifies the responses of materials between ideal solids and Newtonian fluids in soft matter, revealing how weak molecular interactions govern their macroscopic dynamic behavior (Pawde and Dave 2025). The viscosity of a fluid represents friction, and an increase in viscosity indicates an increase in resistance during the extrusion process (Hashemi et al. 2024). This parameter is critical in extrusion‐based additive manufacturing techniques such as 3D printing (Z. Guo, Chen, et al. ²⁰²³). The viscoelastic behavior of bigels is characterized by G′ and G″, which are closely related to the internal microstructure and deformability of the material. G′ represents the resistance to elastic deformation and the ability to store mechanical energy, while G'″ reflects the energy dissipated through viscous flow during deformation.

As summarized in Table 1, W/O systems exhibited higher apparent viscosity, G′, and G″, which are closely related to their internal microstructure (Figure 4A). With the increase of oleogel concentration, the intermolecular interactions are enhanced, and the entanglement and kinking of microstructural segments become more intensive, forming a more stable and solid spatial network structure, which greatly improves the resistance to shear deformation (M. Sun, Wang, et al. ²⁰²⁵; X. Zhao, Wang, et al. ²⁰²⁶). Furthermore, crystal size decreases and crystal number increases with increasing oleogel concentration, leading to a more ordered structure (Pang et al. 2024; Sharifi, Ghiasi, Zare, Hedayati, and Abbasi ²⁰²⁵).

5.1.3. Thermodynamic Properties

Food processing typically involves heating steps (e.g., baking, cooking, sterilization), so evaluating the thermodynamic properties of bigels is of great significance for predicting their suitability in foods.

As summarized in Table 1, W/O systems exhibited higher melting temperature (T _m) and enthalpy change (ΔH), which result from multiple factors, including fatty acid contents and crystal substances, as well as underlying regulatory factors such as crystal polymorphs and oleogelator compositions. For W/O systems, higher fatty acid contents supply a sufficient lipid matrix for oleogelator crystallization, which in turn generates abundant crystalline structures. These crystalline structures induce tight packing of the dispersed phase and synergistically promote the formation of a compact network (Q. Jiang, Chen, et al. ²⁰²⁴; P. Li, Chen, et al. ²⁰²⁵). Furthermore, such a compact network structure can effectively restrict the thermal motion of molecular chains upon heating, delay the thermally induced relaxation and collapse of the network, thereby improving the thermal degradation resistance of bigels (Figure 4B). Beyond fatty acid and crystal contents, studies on oleogels have demonstrated that crystal polymorphs and oleogelator compositions exert regulatory effects on thermal properties. Although rarely explored in bigels, this principle reasonably applies. Lipid crystalline phases commonly form three typical crystal polymorphs with distinct thermal behavior. The α‐crystal possesses a low melting point and poor stability; the β‐crystal features a high melting point, coarse crystal morphology, and superior stability; and the β′‐crystal acts as a metastable intermediate between the α‐ and β‐crystals (Y. Han et al. ²⁰²⁶). These inherent structural differences among three polymorphs are directly reflected in their T _m and ΔH: α‐crystal exhibits low T _m and minor ΔH, β‐crystal shows high Tm and ΔH, while β′‐crystal displays intermediate characteristics. Furthermore, the thermal behavior is modulated by oleogelator compositions via altering crystal polymorphs. Wax‐based oleogels are dominated by β′‐crystal with compact microstructures, fatty acid‐based lipids tend to generate larger crystals based on β‐crystal, whereas composite oleogels typically exhibit more complex mixed polymorphs due to component interactions that interfere with nucleation during crystallization (Y. Han et al. ²⁰²⁶). Combined with the above regulatory mechanism, it can be inferred that the continuous oil phase of W/O systems, which contains abundant oleogel components, enables the formation of an interconnected and dense crystalline network through the regulation of crystal polymorphs. This ordered crystalline skeleton contributes to the improved thermal stability of W/O systems.

Notably, the temperature sweep results showed that G′ and G″ of O/W systems remained high at high temperatures, whereas those of W/O systems decreased more rapidly, indicating that the mechanical properties of W/O systems are highly temperature‐sensitive (Figure 4B). This behavior can be explained by the fact that the crystalline network is primarily responsible for immobilizing the oil phase; however, this network melts at elevated temperatures, causing softening of the oil phase and collapse of the internal crystalline skeleton, thereby weakening the overall gel structure (Santamaría et al. 2026; Teng et al. ²⁰²⁶).

5.2. Long‐Term Stability

Foods often require a certain storage period during actual circulation and consumption. Therefore, systematically analyzing the long‐term storage stability of bigels under different storage conditions is of crucial significance for further clarifying their application value in the food industry.

5.2.1. Oxidative Stability

Bigels comprise both oil and aqueous phases, making them susceptible to lipid oxidation, which can lead to the formation of off‐flavors, discoloration, and the degradation of bioactive components, thereby adversely affecting their functionality and overall shelf life. Therefore, evaluating oxidative stability is essential for assessing the long‐term storage performance of bigels.

As summarized in Table 2, POV and TBARS results indicated that O/W systems exhibited better oxidative stability. The higher oxidative stability observed in O/W systems can be attributed to several factors (Figure 5A). At the interfacial level, interfacial proteins usually contain antioxidant amino acids such as cysteine, which can act as free radical quenchers and metal chelators, thereby facilitating the formation of a compact interfacial barrier (Liao et al. 2026). Moreover, the physicochemical properties of emulsifiers govern the formation and stability of the interfacial layer. These emulsifiers can rapidly adsorb at the oil–water interface to form a compact interfacial film (L. Liu, Yang, et al. ²⁰²⁵), which acts as a physical barrier and further hinders the diffusion of pro‐oxidative components from the aqueous phase to the oil phase. Regarding the spatial localization of pro‐oxidants and antioxidants, water‐soluble antioxidants enriched at the oil–water interface can act as preferential sacrificial sites for pro‐oxidants, thereby hindering the diffusion of pro‐oxidants, protecting critical amino acids and the protein backbone from oxidation, and further effectively retarding lipid oxidation (J. Chen, Liang, et al. ²⁰²³). In conclusion, the superior oxidative stability of O/W systems is governed by a synergistic interplay of multiple factors rather than a single mechanism.

TABLE 2.

Long‐term stability of different bigel systems induced by phase inversion.

Long‐term stability	Optimal system	Different bigel systems	Storage conditions	Key formulation parameters	Performances	References
Oxidative stability	W/O	W/O Bi‐continuous O/W	25°C for 35 days	Hydrogel: Gellan gum (1.2%, w/w) Oleogel: Glycerol monostearate (4%, w/w) Palm oil:Algae oil = 1:1	● POV and TBARS ↓	Wei et al. (2025)
	O/W	W/O Bi‐continuous O/W	50°C for 14 days	Hydrogel: Gelatin: Carboxymethyl chitosan = 1:1, 1:2, 2:1 (4 %, w/w) Oleogel: Beeswax (8%, w/w) Soybean oil	● POV and TBARS ↓	L. Li, Feng, et al. (2025)
	O/W	W/O O/W	5°C for 63 days	Hydrogel: Agar (2%, w/w) κ‐carrageenan (1%, w/w) Oleogel: Sunflower wax (10%, w/w) or Sunflower wax: Monoglycerides = 1:1 (10%, w/w) Olive oil	● POV ↓	Dimakopoulou‐Papazoglou et al. (2025)
	O/W	W/O Bi‐continuous O/W	12 days	Hydrogel: Low acyl gellan gum (0.8%, w/w) or high acyl gellan gum (0.8%, w/w) Oleogel: Glyceryl monolaurate (10%, w/w) Rapeseed oil	● POV and TBARS ↓	X. Wang et al. (2024)
	O/W	W/O O/W	40°C for 14 days	Hydrogel: Gelatin (10%, w/w) Oleogel: Glyceryl monostearate (9%, w/w) Fish oil	● Stable appearance ● POV and TBARS ↓	M. Sun, Wang, et al. (2025)
Freeze–thaw stability	W/O	W/O Bi‐continuous O/W	−20°C for 24 h, 25°C for 24 h	Hydrogel: Whey protein isolate (2.5%, w/w) Gelatin (2.5%, w/w) Oleogel: Beeswax:Plant sterol ester = 6:4 (20%, w/w) Diacylglycerol corn oil	● Stable appearance ● Oil binding capacity ↑	Qian et al. (2025)
	W/O	W/O Bi‐continuous O/W	−20°C for 6 h, 25°C for 6 h, 12 cycles	Hydrogel: Potato protein (12%, w/v) Carboxymethyl chitosan (1.5% or 3%, w/v) Oleogel: Glycerol monostearate (10%, w/v) Corn oil	● Solvent holding capacity ↑	X. Zhao, Wang, et al. (2026)
	O/W	W/O Bi‐continuous O/W	−20°C for 24 h, 28°C for 24 h, three cycles	Hydrogel: Low acyl gellan gum (0.8%, w/w) or High acyl gellan gum (0.8%, w/w) Oleogel: Glyceryl monolaurate (10%, w/w) Rapeseed oil	● Stable appearance ● Oil holding capacity ↑	X. Wang et al. (2024)
	O/W	W/O Bi‐continuous O/W	−20°C for 22 h and ambient temperature for 2 h, three cycles	Hydrogel: Carboxymethyl cellulose (6%, w/w) Oleogel: Ethyl cellulose (15%, w/w) Canola oil	● Solvent holding capacity ↑	Perera et al. (2026)
	O/W	Bi‐continuous O/W	−20°C for 24 h and room temperature for 24 h, three cycles	Hydrogel: Gelatin (10%, w/w) Oleogel: Beeswax (6%) Rice bran wax (4%) Soybean oil	● Oil holding capacity ↑	Zhou et al. (2025)
	O/W	W/O Bi‐continuous O/W	−20°C for 24 h and room temperature for 24 h, three cycles	Hydrogel: κ‐carrageenan (2%, w/w) Starch (0% or 10%, w/w) Oleogel: Beeswax (20%, w/w) Soybean oil	● Oil holding capacity ↑	M. Zhou et al. (2024)
	O/W	W/O Bi‐continuous O/W	−20°C for 4 h, 25°C for 6 h, four cycles	Hydrogel: Gelatin (10%, w/w) Oleogel: Glyceryl monostearate (9%, w/w) Fish oil	● Stable appearance and water distribution	M. Sun, Wang, et al. (2025)

FIGURE 5.

Oxidative stability (A), freeze–thaw stability (B), and in vitro digestion behaviors (C) of different bigel systems induced by phase inversion.

5.2.2. Freeze–Thaw Stability

The water in hydrogels undergoes crystallization when exposed to freezing temperatures. Ice not only occupies a larger volume than water, thereby reducing the space between oil phases and allowing oil droplets to accumulate closely, but can also severely destroy the entire network structure, causing interfacial collapse and phase separation during thawing (Cho et al. 2023; M. Zhou et al. ²⁰²⁴). The gel network accommodates liquid oil, which will leak out upon rupture of the gel network, leading to structural deterioration. Therefore, comparing the freeze–thaw stability of different bigel systems can promote the application of bigels in foods.

As summarized in Table 2, O/W systems exhibited better freeze–thaw stability than W/O and bi‐continuous systems. The superior freeze–thaw stability of O/W bigels may be attributed to the following reasons, as schematized in Figure 5B. At the structural level, O/W systems exhibited excellent springiness (Table 1), endowing them with favorable deformability and buffering capacity during freezing, which allow them to effectively counteract the volume expansion induced by ice crystal growth, thereby achieving rapid structural recovery after thawing. Furthermore, the presence of hydrogels can provide additional structural support for oleogels, thus reducing the leakage of liquid oil (M. Zhou et al. ²⁰²⁴).

5.3. In Vitro Digestion Behavior

The digestion and release kinetics of lipids directly regulate postprandial lipid response and energy metabolism, and a moderately delayed release rate of free fatty acids is more beneficial for metabolic health when applied as fat replacers. Therefore, comparing the release rates of free fatty acids in different bigel systems is of great scientific significance for clarifying the intrinsic relationship between their structure and health effects.

As summarized in Table 1, W/O systems exhibited lower free fatty acid release during in vitro digestion, suggesting their potential as fat replacers for achieving slow lipid digestion. This can be attributed to the mechanisms illustrated in Figure 5C. W/O systems present a more continuous and stable crystalline network (X. Zhao, Wang, et al. ²⁰²⁶). This network acts as a physical barrier that renders them more resistant to disintegration during simulated digestion, thus hindering bile salt‐mediated lipid emulsification, delaying bulk oleogel breakdown, and limiting lipase accessibility, which ultimately results in reduced lipid digestion (Q. Jiang, Chen, et al. ²⁰²⁴).

5.4. Comprehensive Evaluation on the Properties of Different Bigel Systems and Their Application Prospects in Fat Replacers

In summary, different bigel systems exhibit differences in functional properties. Specifically, W/O systems show higher hardness, chewiness, viscosity, G′, G″, T _m, and ΔH, together with a lower release rate of free fatty acids. In contrast, O/W systems present superior springiness, cohesiveness, high‐temperature structural stability, oxidative stability, and freeze–thaw stability. Bi‐continuous bigels exhibit intermediate properties between hydrogels and oleogels in all aspects. Accordingly, these structure‐dependent functional differences endow different bigel systems with distinct application potentials in foods (Figure 6A).

FIGURE 6.

Comparison of the functional performances of different bigel systems as animal fat replacers (A) and current status and trends (B). The images are referenced from published studies (Hernández‐Nolasco et al. ²⁰²⁵; Q. Jiang, Chen, et al. ²⁰²⁴; Kang and Imm ²⁰²⁵; Sharifi et al. ²⁰²⁵; Wu et al. ²⁰²⁵; Zennoune et al. ²⁰²²). All images are reprinted with permission from Elsevier.

Overall, W/O systems exhibit promising potential in oil‐loading capacity, structural stability and health‐related properties, indicating they may act as candidate fat replacers for meat product development. First, W/O systems exhibit a high oil‐loading capacity and could function as effective carriers for flavor compounds, which have the potential to enrich the aroma intensity and taste complexity of meat matrices and optimize overall sensory attributes. Second, W/O systems possess favorable structural strength and physical stability. They can maintain a well‐defined 3D network structure during meat product processing, effectively preventing oil migration and exudation, thereby improving the texture and flavor of the products. Third, G′ and G″ decrease under high‐temperature heating, which may contribute to juicier and tenderer mouthfeel of cooked meat products. Finally, the low release rate of free fatty acids observed during in vitro digestion implies their potential to mitigate health risks associated with excessive lipid intake. This characteristic makes W/O systems consistent with the development concept and market demand for modern healthy meat products. Notably, direct investigations into the application of W/O systems in meat products remain quite limited. The aforementioned favorable characteristics and potential health benefits are only inferences supported by indirect evidence, not definitive conclusions. Systematic verification with meat matrices is required in future studies.

O/W systems possess excellent springiness, cohesiveness, as well as high‐temperature, oxidative, and freeze–thaw stability, which meets the key demands of processing and storage for bakery products. First, their superior springiness and cohesiveness contribute to enhanced dough extensibility, enabling bakery products to exhibit a regular morphology and uniform texture. Second, their outstanding high‐temperature structural stability ensures structural integrity during baking, effectively suppressing collapse, cracking, and excessive shrinkage. Third, their excellent oxidative stability effectively mitigates lipid oxidation and rancidity in bakery products, thereby prolonging shelf life and preserving flavor. Finally, semi‐finished bakery products (e.g., frozen dough and frozen cakes) frequently undergo repeated freeze‐thaw cycles, and the outstanding freeze–thaw stability of O/W systems prevents product cracking and water exudation, thus ensuring desirable quality after thawing.

Bi‐continuous systems possess interconnected 3D gel networks, which combine the properties of hydrogels and oleogels, exhibiting significant advantages in 3D‐printed foods. First, their excellent extrudability ensures a continuous and smooth printing process without nozzle clogging or filament breakage. Second, their appropriate structural strength and self‐supporting capacity enable the accurate shaping of printed products, preventing collapse or layer separation. Therefore, bi‐continuous systems are more suitable as ideal inks for high‐precision and high‐stability 3D‐printed foods.

6. Applications of Different Bigel Systems in Foods

As a typical class of soft matter, bigels exhibit functional properties that reveal how their microstructures regulate practical application performance, thereby establishing the inherent structure–function–application relationship. To design suitable bigel systems for specific foods, it is essential to comprehensively balance the key factors, including food categories, functional requirements, optimal bigel system, applied foods, key formulation parameters, and performances. On this basis, the applications of different bigel systems in foods are compared in the following section (Table 3).

TABLE 3.

Comparison of the functional performances of different bigel systems as animal fat replacers in different food matrices.

Food categories and functional requirements	Optimal system	Different bigel systems	Applied foods	Key formulation parameters	Performances	References
3D‐printed foods ▸Flowability and extrudability ▸Adequate mechanical strength and self‐supporting ability ▸Health	W/O	W/O Bi‐continuous O/W	Inks	Hydrogel: Carrageenan:Xanthan gum = 1:1 (1.5%, w/w) Oleogel: Beeswax (15%, w/w) Corn oil	● Excellent self‐supporting and shape‐retaining properties	R. Qiu et al. (2022)
	Bi‐continuous	W/O Bi‐continuous O/W	Inks	Hydrogel: C. pyrenoidosa protein (10%, w/v) Xanthan gum (0.5%, w/v) Oleogel: Beeswax (4%, w/v) Camellia oil	● Excellent self‐supporting characteristics and printing accuracy	Q. Jiang, Chen, et al. (2024)
	Bi‐continuous	W/O Bi‐continuous O/W	Inks	Hydrogel: Carboxymethyl cellulose (6%, w/w) Oleogel: Ethyl cellulose (15%, w/w) Canola oil	● Shape inconsistency factor ↓ ● Deformation factor ↑ ● Grid‐like architecture with minimal sagging or strand fusion	Perera et al. (2026)
	Bi‐continuous	W/O Bi‐continuous O/W	Inks	Hydrogel: Low acyl gellan gum (2%, w/w) Oleogel: Beeswax (2%, w/w) Algae oil	● Smooth and complete appearance with minimal printing unevenness ● Height and length closely matched the target shape	Chao, Yan, et al. (2024)
	O/W	O/W Bi‐continuous W/O	Inks	Hydrogel: Hydroxypropyl methylcellulose (3%) Oleogel: Beeswax (10%) Polyglycerol polyricinoleate (1%) Soybean oil	● Superior performance in models with small‐area monolayer structures ● Extrusion‐stable without damage	Z. Chen, Bian, et al. (2023)
Meat products ▸Flavor and sensory properties ▸Excellent juiciness after heating ▸High hardness and viscoelasticity ▸Excellent storage stability ▸Health	W/O	W/O	T1: Model meat product T2: Hamburger‐type meat product	Hydrogel: Potato starch (10% w/w) κ‐carrageenan (2% w/w) Oleogel: Beeswax (10% w/w) Canola oil	75% (Replacement: 0%, 25%, 50%, 75%, and 100%) ● T1: greater cooking loss and shrinkage ● T2: improved thermal stability	Hernández‐Nolasco et al. (2025)
	W/O	W/O	Low‐fat burgers	Hydrogel: Wheat starch (10%, w/w) Oleogel: Ethylcellulose (10%, w/w) Sunflower oil	75% (Replacement: 0%, 25%, 50%, and 75%) ● Excellent mechanical properties ● Lower cooking shrinkage and loss ● Comparable color, odor, flavor, appearance, and general acceptability to the control	Ghiasi and Golmakani (2022)
	Bi‐continuous	Bi‐continuous	Meat patties	Hydrogel: Gelatin (1% w/w) Sesbania gum (3.0%, w/w) Oleogel: Beeswax (10%, w/w) Flaxseed oil	● Mechanical resilience well maintained ● Higher lightness and lower yellowness ● Overall acceptability comparable to the control	X. Liu, Ma, et al. (2025)
	O/W	O/W	Tender fish balls	Hydrogel: Gelatin (17%) Oleogel: Beeswax (10%, w/w) Sunflower oil (w/w)	50% (replacement: 0%, 25%, 50%, 75%, and 100%) ● Increased moisture content, freshness, and flavor richness, without affecting texture and water activity ● Improved the microstructure during freeze–thaw cycles	Gao et al. (2025)
	O/W	O/W	Semi‐dry sausages	Hydrogel: κ‐carrageenan (2%, w/w) Gelatin (4%, w/w) Oleogel: Monoglycerides (15%, w/w) Olive oil	50% (replacement: 0% and 50%) ● Comparable hardness, cohesiveness, and liking scores to the control, no undesirable sensory attributes	Zampouni et al. (2024)
Bakery products ▸Excellent structural stability during baking ▸Excellent extensibility enables effective retardation of dough hardening ▸Excellent storage stability ▸Health	W/O	W/O	Bread	Hydrogel: Chestnut starch (5%, w/w) Oleogel: γ‐oryzanol:β‐sitosterol = 3:2 (10%, w/w) High oleic sunflower oil	50% (Replacement: 0%, 25%, 50%, 75%, and 100%) ● Similar pore structure, cohesiveness, and elasticity to the control ● Sensory score closest to the control	Ma et al. (2025)
	Bi‐continuous	Bi‐continuous	Cookies	Hydrogel: Cellulose nanofibers (0.6%, w/w) Oleogel: Glycerol monostearate (10%, w/w) Sunflower seed oil	25% (Replacement: 0%, 25%, 50%, 75%, and 100%) ● Similar L*, a*, diameter, and thickness to the control	Hou et al. (2024)
	Bi‐continuous	Bi‐continuous O/W	Bread	Hydrogel: Hydroxypropyl methylcellulose (2%, w/w) Oleogel: Beeswax (0 and 8%, w/w) Diacylglycerol	50% (Replacement: 0% and 50%) ● Similar shape, texture, and total scores to the control ● Highest ratings and greatest similarity to the control in characterization and sensory scores	X. Lin et al. (2025)
	O/W	O/W	Bread	Hydrogel: Locust bean gum (2% w/w) κ‐carrageenan (1% w/w) Oleogel: Soy protein isolate:Citrus fiber = 90:10 (6.25%, w/w) Flaxseed oil	● Increased specific volume, reduced crumb hardness, and enhanced cohesiveness.	Kang and Imm (2025)
	O/W	O/W	Cookies	Hydrogel: κ‐carrageenan (1%, w/w) Oleogel: Monoglyceride (10%, w/w) Sunflower oil	25% (replacement: 0%, 25%, 50%, 75%, and 100%) ● Comparable cooking loss to the control ● Excellent oxidation stability	Sharifi et al. (2025)

6.1. 3D‐Printed Foods

3D printing, as a technology that converts digital designs into three‐dimensional objects through three key stages, namely 3D modeling, path planning, and physical printing, enables highly flexible and intelligent printing without mechanical machining or molds, thus optimizing production models (X. Zhou, Ge, et al. ²⁰²⁵). Benefiting from this merit, food 3D printing has emerged as a promising strategy for personalized nutrition and customized food geometries. However, the application of this technology highly depends on the printability of food‐grade materials, which are required to exhibit excellent extrudability, flowability, self‐supporting ability, and post‐printing shape retention (Cen and Meng 2024). Crucially, these printing performances are governed by the well‐balanced viscoelasticity and structural rigidity of materials (Y. Zhao, Shi, et al. ²⁰²⁶). Traditional plastic fats possess the above properties to meet printing performance requirements, but their high saturated fatty acid content contradicts the current concept of healthy eating. In this context, bigels, as a composite gel system co‐constructed by oil and aqueous phases, have emerged as ideal inks for 3D‐printed foods.

As summarized in Table 3, bi‐continuous systems are more suitable for 3D‐printed foods. Ink viscosity is crucial for 3D printing as high viscosity can enhance shape retention and layer stability, but may lead to nozzle clogging; low viscosity can make ink flow smoother, but may affect structural integrity (Hanbeyoglu‐Akturk et al. ²⁰²⁵). Therefore, compared with W/O and O/W systems, the moderate viscosity, G′, and G″ of bi‐continuous systems enable them to achieve a balance between extrusion smoothness and structural retention. Nevertheless, this observation should not be generalized as a universal principle. In fact, appropriately formulated W/O and O/W systems can also achieve excellent printing performance. For instance, R. Qiu et al. (2022) reported that W/O systems, formulated as printing inks consisting of carrageenan/xanthan gum‐based hydrogel (1.5%, 1:1) and beeswax‐based oleogel (15%), exhibited excellent self‐supporting and shape‐retaining properties. Z. Chen, Bian, et al. (2023) demonstrated that O/W systems, formulated as printing inks consisting of hydrogel containing hydroxypropyl methylcellulose (3%) and oleogel containing beeswax (10%) and PGPR (1%), showed superior performance in small‐area monolayer structures with stable extrusion. These findings indicate that, in addition to bi‐continuous systems, well‐formulated W/O or O/W systems can also serve as viable high‐precision 3D printing inks.

6.2. Meat Products and Bakery Products

Traditional meat products require large amounts of fat to achieve the desired texture, taste, and flavor (X. Hu et al. ²⁰²³). Similarly, in the processing of bakery products, margarine and shortening, as typical viscoelastic semi‐solid raw materials, play a crucial role (Rohm et al. 2018). Given the high fat content in meat products and bakery products, together with the associated health risks, the development of effective fat replacers has become an inevitable trend. Bigels are ideal candidate materials in this field owing to their unique structural and functional properties.

As shown in Table 3, it is difficult to identify the optimal bigel systems for meat products and bakery products. The main reason is that existing studies have not applied different bigel systems to the same foods for parallel comparison, but have directly adopted the suitable systems determined by preliminary experiments. In contrast to research on 3D‐printed foods, studies focusing on meat and bakery products place more emphasis on the effects of fat replacement ratio on product quality.

Partial fat replacement with bigels enables the production of high‐quality foods, whereas complete fat replacement negatively impacts product quality. First, when the fat replacement ratio is high, the oxidation of products during storage increases significantly (Sharifi et al. 2025), which may be attributed to the high unsaturated fatty acid content in bigels. Second, an increase in fat replacement ratio results in deterioration of appearance, indicating discontinuity of the internal matrix (Hou et al. 2024). Finally, an excessive fat replacement ratio exerts significant negative effects on product texture and reduces sensory scores for flavor and odor (Ghiasi and Golmakani 2022).

7. Trends

Based on the above overview and analysis of the functional properties and current applications of bigels, future development trends are illustrated in Figure 6B.

7.1. Interactions Between Bigels and the Components in Foods

Gao et al. (2025) evaluated the efficacy of bigels prepared using a two‐step cold‐set method as partial replacers of pork fat in tender fish ball formulations. J. Hu et al. (2025) prepared bigels using potato starch‐based hydrogels and walnut oil/candelilla wax‐based oleogels to produce low‐fat margarine. At present, research on bigels as fat replacers mainly adopts the direct application method; in other words, bigels are directly incorporated into foods (e.g., meat products, dairy products, and baked goods) to explore their impacts on physicochemical properties, sensory quality, and nutritional functions. This approach enables direct assessment of bigels’ efficacy as fat replacers in food applications. However, it often lacks a comprehensive analysis of interfacial interactions, phase behavior dynamics, and structure–function relationships. Other types of fat replacers have been systematically studied to clarify the structure–function relationships between fat replacers and major components of food matrices (such as proteins, carbohydrates, and lipids) from the perspective of molecular interactions. For example, C. Huang et al. (2024) explored the effects of polysaccharide addition on the gel properties, microstructure, and digestive properties of myofibrillar proteins. X. Zhou et al. (2019) studied the effects of fat type and concentration on fish myofibrillar protein–lipid composite gels. However, the interactions between bigels and other food components remain relatively unclear. Subsequent research should systematically analyze the molecular interactions between bigels and primary constituents in the food matrix (proteins, carbohydrates, and lipids) to establish their fat‐mimetic mechanisms.

7.2. Interrelationship Between Sol–Gel Transition Temperatures of Proteins/Polysaccharides and Crystallization Temperatures of Oleogels

Current research on bigels has mainly focused on the optimization of component ratios and preparation processes, while systematic research on the temperature synergy mechanism remains insufficient. The intrinsic relationship between the sol–gel transition temperatures of polysaccharides/proteins and the crystallization temperature of oleogels has not been systematically elucidated.

Polysaccharides exhibit characteristic sol–gel transition temperatures. Similarly, proteins possess thermally induced or cold‐set gelation temperatures, while oleogels formed by waxes, monoglycerides, and other components show corresponding crystallization and melting temperatures. Whether the characteristic temperatures of these components are matched directly determines the interpenetrating degree of the networks and interfacial stability. A stable interpenetrating network structure is more likely to be formed when the gelation temperature of polysaccharides or proteins is close to the crystallization temperature of oleogels, resulting in denser and more stable bigels. Conversely, an excessive temperature difference among these components tends to cause phase separation and network destruction, ultimately leading to a significant decrease in the physical stability. Therefore, the design and construction of highly stable bigels with temperature synergy and compatibility as the core strategy exhibit broad research prospects and application potential.

Cui et al. (2026) found that adjusting the concentration of (−)‐epigallocatechin‐3‐gallate could affect the sol–gel transition of tamarind seed polysaccharide. Specifically, with increasing concentration, the sol–gel transition temperature increased, and the network cross‐linking density gradually increased during the cooling process. L. Qiu et al. (2024) prepared temperature‐responsive gel inks using κ‐carrageenan, fenugreek gum, rose extracts, and sucrose. The results showed that the addition of fenugreek gum increased the gelation temperature of the inks from 39.7°C to 44.7°C–49.6°C. These findings provide a theoretical and experimental basis for the temperature regulation and structural design of bigels.

7.3. Enhancement of Bigel Stability via Physical and Chemical Strategies

To improve the physical stability of bigels, physical modification strategies are proposed to enhance the functional properties of proteins, with a particular focus on plant proteins. Owing to their complex structure, high density, and strong sensitivity to external factors, plant proteins generally exhibit poor functional properties that hinder their processing and application in the food industry, thereby driving a growing number of studies focused on improving these properties via physical modification techniques (Kong et al. 2025). Among these, heating modification has become a common method for the physical modification of plant proteins due to its low cost, simple operation, and high cost‐effectiveness (Kong, Chen, et al. ²⁰²⁶). C. Li et al. (2023) investigated the effect of different heat treatment times at 80°C on the structural and functional properties of Phaseolus vulgaris L. protein and confirmed that heat treatment modified its structure and improved its foamability, emulsification, and digestibility. In addition, emerging physical technologies such as ultrasound, high pressure, cold plasma, pulsed electric field, and ionizing irradiation modifications can also effectively improve the functional properties of plant proteins (Kong et al. 2025). However, the application of the above‐mentioned emerging physical modification technologies in bigels remains insufficient, which presents promising research and application prospects.

Furthermore, chemical modification mainly improves the solubility, emulsification, and foaming capacity of plant proteins by altering their secondary and tertiary structures (Kong, Liu, et al. ²⁰²⁶). The enhanced solubility and emulsification contribute to better gelation performance of proteins, thereby improving the physical stability of bigels.

J. Guo, Gu, et al. (2023) prepared S. platensis protein nanoparticles/xanthan gum‐based bigels. Tian et al. (2023) used a combination of konjac glucomannan and gelatin as the hydrogel component in bigels. At present, strategies for improving the stability of bigels mainly rely on the synergistic interactions among polysaccharides and proteins, while the role of polyphenols is often overlooked. Polyphenols have been widely applied in other fat replacers. X. Han, Niu, et al. (2025) prepared Pickering emulsions stabilized by Flammulina velutipes protein, F. velutipes soluble polysaccharide, and tea polyphenol particles, which exhibited favorable thermal, centrifugal, storage, and oxidation stability. Z. Zhang et al. (2023) indicated that the addition of sodium alginate led to more stable soybean protein isolate–quercetin complexes with improved emulsifying, foaming, and antioxidant properties. Therefore, exploring the binding between polyphenols and proteins, as well as the binding among polyphenols, polysaccharides, and proteins, is crucial for improving the stability of bigels in the future.

7.4. Processing Stability of Bigels Under Different Processing Conditions

Ionic strength, pH value, and homogenization conditions (i.e., speed and time) are key process parameters for regulating the quality of bigels. Their changes directly affect the microstructure, interfacial stability, and macroscopic physical properties of bigels. Therefore, systematically investigating the effects of the above conditions on the stability of bigels can provide a theoretical basis for optimizing the preparation process and improving the stability of product quality.

H. Wang et al. (2026) investigated the stability of bigels under different ionic strengths (0, 100, 500 mM) and pH values (2 and 7). L. Li, Feng, et al. (2025) observed the encapsulation efficiency of bigels under cyclic pH conditions. Gao et al. (2025) investigated the properties of bigels under different pre‐dispersion speeds and times, along with different homogenization times. The aforementioned studies have conducted valuable explorations on the environmental stability of bigels. However, they still have certain limitations: most studies focus on the environmental stability of a single bigel system, and fail to systematically compare the differences between different bigel systems and analyze the underlying mechanisms. This makes it difficult to reveal the intrinsic correlation between structural characteristics and environmental stability. Future research can further focus on investigating the environmental stability of different bigel systems under varying ionic strength, pH value, and homogenization conditions.

7.5. Comprehensive and Objective Sensory Evaluation of Bigels

M. Sun, Wang, et al. (2025) conducted a preference test to evaluate the acceptability of low‐fat mayonnaise prepared from fish oil‐based bigels. Zampouni et al. (2024) conducted a sensory evaluation using a 9‐point hedonic scale rating test to assess semi‐dry sausages with bigels as fat replacers. The sensory panel ranked the sausage samples according to preference.

While sensory evaluation is crucial for assessing consumer acceptance, it has several notable limitations, including insufficient investigation into flavor and taste mechanisms. Advanced analytical techniques, including e‐nose and e‐tongue, offer significant advantages in measurement precision and objectivity compared to conventional sensory methods. In addition, oral tribology, which measures the friction coefficient between the tongue and palate, provides critical insights into the lubrication properties of fat replacers. Integrating e‐nose, e‐tongue, and oral tribology with sensory evaluation is essential for establishing a reliable relationship between instrumental measurements and human sensory perception.

Gao et al. (2025) used an e‐tongue to assess the taste characteristics of tender fish balls with bigels as fat replacers. Du et al. (2025) investigated the oral tribology of natural oleanolic acid‐based W/O Pickering emulsions. Du and Meng (2025) determined the oral tribology of a Pickering O/W/O emulsion gel‐based fat analogue. Therefore, future research should prioritize developing standardized instrumental methods (e‐nose, e‐tongue, and oral tribology) for assessing the sensory properties of bigel‐based fat replacers in foods.

7.6. Emerging Advanced Characterization Techniques for bigels

While this review has focused on established methods such as CLSM, SEM, PLM, and MRI, emerging techniques offer new opportunities for understanding bigel structure. Micro‐computed tomography (micro‐CT) is a non‐destructive characterization technique, which enables the visualization of internal microstructures in materials by reconstructing 3D volume data across various spatial scales (Olakanmi et al. 2023). It enables the quantification of porosity and pore size, connectivity, pore structure, and tortuosity in 3D space, which combines the 3D visualization and morphological parameter extraction to study microstructure at high resolution (G. Li, Li, et al. ²⁰²⁴). Micro‐CT has been successfully used to characterize related foods, such as fried potato chips (J. Zhang et al. ²⁰²⁴), sponge cake (Zennoune et al. 2022), and so on. Although its application in phase inversion of bigels has not yet been reported in the literature, it exhibits promising application prospects and great potential in this field.

Although current rheological characterization encompasses conventional parameters such as apparent viscosity, G′, and G″, more accurate quantitative rheological indices, such as linear viscoelastic region (LVR) and Boltzmann sigmoidal model should be adopted in future studies. The LVR refers to the low‐deformation regime where G′ and G″ remain essentially constant (X. Zhang et al. ²⁰²⁶). The end of the LVR is generally defined as the critical strain point at which the G′ falls to 5% below its plateau value measured at low strains, beyond which the internal network structure begins to undergo irreversible breakdown and the material enters the nonlinear viscoelastic region (Ryu and McClements ²⁰²⁵; X. Zhang et al. ²⁰²⁶). In general, a wider LVR indicates that the material can maintain structural integrity over a broader strain range, reflecting stronger structural stability (Cofelice et al. 2023). However, despite the widespread application of the LVR as a quantitative rheological parameter in various fat replacers, research on the LVR of bigels remains limited. Applications of Boltzmann sigmoidal model are primarily focused on non‐food systems, such as conformational transitions in polymer solutions (Bouali et al. 2026), multi‐phase flows (Lautenschlaeger et al. 2022), and solute transport in dual‐permeability media (J. Huang et al. ²⁰²³). In contrast, the application of the Boltzmann sigmoidal model in foods, particularly in fat replacers, remains extremely limited. Nevertheless, this model quantitatively characterizes the recovery behavior of bigels post‐shear, thereby simulating the recovery of their native texture after oral processing. Therefore, future research should gradually focus on validating the practical applicability of this model for bigels.

7.7. Bigel‐Based Scaffolds for Mimicking Adipose Tissue in Cultured Meat

The sustained growth of the global population, coupled with rising living standards, has driven an increasing demand for high‐protein meat products (Z. Sun, Yin, et al. ²⁰²⁵). However, conventional livestock production is a resource‐intensive process that requires substantial inputs of land, water, and energy (Chiu et al. 2025). In this context, cultured meat, which is produced by proliferating and differentiating animal cells in vitro, has emerged as a promising alternative (Que et al. 2025). Notably, its commercialization faces the challenge of high production costs. To reduce production costs, cultured meat, which should ideally be composed of mature muscle fibers, connective tissue, and adipose tissue, can be combined with economical and scalable biomaterials that serve as scaffolds to support cell growth and provide desirable texture (Geurs et al. 2025). Therefore, the development of biomaterial scaffolds has become the most critical technical bottleneck in this field (L. Li, Zhang, et al. ²⁰²⁵).

Protein‐based materials have attracted increasing attention in cultured meat due to their high cytocompatibility and biodegradability, while polysaccharides are widely used in scaffolds owing to their natural porosity, biocompatibility, and chemical modifiability (Qin et al. 2026). Pei et al. (2025) prepared dual‐crosslinked protein‐based hydrogel scaffolds via a two‐step crosslinking method. These scaffolds exhibited superior structural and physical properties, promoted myocyte adhesion, proliferation, and differentiation, and produced products with texture close to natural pork. Kim et al. (2025) prepared edible gelatin/chitosan cryogel scaffolds with porous structures. These scaffolds have sustainable raw materials and tunable physicochemical properties, which can effectively support the growth of bovine muscle cells and form cultured meat with structure and texture similar to natural steak.

Various protein‐ and polysaccharide‐based hydrogels exhibit sufficient mechanical properties and cytocompatibility to support myocyte culture. However, cultured meat often lacks the effective integration of adipose tissue, which directly limits the texture, flavor, and mouthfeel of products (Sajib et al. 2026). Sajib et al. (2026) constructed bigel scaffolds with suitable hardness and excellent biocompatibility, which can effectively support cell proliferation and differentiation, and this lipid integration strategy exhibited great potential in regulating the texture, flavor, and nutritional properties of whole‐cut cultured meat. Notably, differing from conventional hydrogel scaffolds, bigels feature a distinctive biphasic structure that permits independent tuning of the mechanical behavior of the hydrogels and the lipid profile of the oleogels, thus conferring prominent superiority for adipose tissue engineering applications. Therefore, although research on bigels as scaffolds remains relatively limited, the above studies clearly indicate their great potential as promising candidate scaffold materials.

8. Conclusion

Compared to direct fat reduction and conventional fat replacers, bigels exhibit superior performance as animal fat replacers. The formation of bigels is collectively governed by hydrogelator assembly, oleogelator crystallization, and emulsifier‐stabilized interfaces. Meanwhile, the functional properties of bigels are governed by their phase inversion behavior, which is mainly modulated by the oil‐to‐water ratio. Among different bigel systems, W/O systems exhibit enhanced texture and rheological properties, and low free fatty acid release, while O/W bigels exhibit superior oxidative and freeze–thaw stability. Regarding the application of bigels as fat replacers in foods, bi‐continuous systems have shown favorable suitability for 3D‐printed food, whereas the optimal system for application in meat and bakery products remains difficult to identify. Finally, based on the current research, this review summarizes the emerging trends in this field, including interactions between bigels and food components, temperature matching between hydrogel and oleogel formation, improvements in stability and processability, advanced sensory and characterization techniques, as well as applications of bigel‐based scaffolds for adipose tissue engineering in cultured meat. Such advancements open new possibilities for formulating low‐fat foods that achieve optimal texture and sensory appeal.

Author Contributions

Yuexin Li: investigation, writing – original draft, writing – review and editing. Yuhang Fan: conceptualization, writing – review and editing. Qian Chen: writing – review and editing. Qian Liu: supervision, writing – review and editing. Hui Wang: investigation, writing – review and editing. Haotian Liu: conceptualization, writing – review and editing. Baohua Kong: conceptualization, supervision, funding acquisition, project administration, writing – review and editing.

Conflicts of Interest

The authors declare no conflicts of interest.