Besides existing as an emulsion, complex colloidal materials can also exist as gels. Oil-in-water (O/W) emulsions based on fluids can be transformed into soft-solids known as emulsion gels or emulgels (EGs), which can be conceptualized as either a network of cross-linked polymers with embedded emulsion droplets (referred to as emulsion-filled gels, or EFGs), or as a network made of flocculated droplets [1] with different physicochemical and physiological properties. EGs can be used as fat substitutes and are the fundamental building blocks of numerous meals, including cheese, yogurt, and sausage [2]. For bioactive components like β-carotene, vitamins, probiotics, etc., EGs are effective delivery vehicles [[2], [3], [4]]. The restricted mobility of the embedded components is made possible by the tight gel networks, which can also serve as a deterrent to outside attacks. In contrast to EGs, which have gained more attention over the past ten years due to their advantages such as the prolongation of gastric and/or intestinal transit time due to the gel's protection [5], and more resistance during storage since the EG can build natural barriers to oil movement and create obstructed oxygen transport within the lattice [[6], [7], [8]], emulsions delivery systems have only a little scope for enhanced in vivo bioavailability of nutraceutical compounds [9].

The gel matrix is made up of substances with the power to form unique gels, primarily proteins, and polysaccharides. According to the differences in the gel matrix, EGs can be separated into three types: bulk EGs, EG particles, and fluid EGs [10]. Lipid droplets in EGs can be categorized as active and inactive fillers [11] depending on how they interact with gelling agents and emulsifiers to change the properties of EGs [12]. The kind, concentration, structure, and interactions of an EG's structural constituents, e.g., oil droplets, proteins, polysaccharides, and cross-linking (CL) agents, determine its macroscopic physicochemical characteristics, including appearance, texture, and stability [2,13,14].

The EFGs, which are made up of floating particles, or particles trapped by the gelled network, may address textural difficulties [[15], [16], [17], [18]]. Such intricate systems have attracted a great deal of interest because of their rheological behavior, which is of paramount importance since it influences the processing environment, sensory perception, and long-term stability [18,19]. The aggregation and CL of protein and polysaccharide biopolymers into 3D solid-like hierarchical structures (or “gels”) is one of the primary techniques for the production of microstructure with desired textural qualities. There are multiple different EGs that can be made, each having different structure-property-functionality relations and use. As a result, the rheological characteristics of EGs created using diverse procedures vary, and these differences are related to the acceptability, processability, and uses of EGs [20]. A generic approach to create EGs by using glucono-δ-lactone (GDL), heat treatment, the addition of divalent salts (CaCl2, ZnCl2 or MgCl2), or even enzymatic CL with glutaminase has been put forward for a long time [2,21,22]. Recent years have seen a surge in interest in cold-set gelation [23,24] for the enclosing of either semi-tolerant acid- and/or heat-stimulated nutraceutical materials, like antimicrobials, antioxidants, aromas, colors, and vitamins [25].

It is possible to use knowledge about the rheology of EGs as an accurate tool to provide a comprehensive assessment of the structural organization and interactions of the components by being able to compute the relaxation time spectrum of EGs [26]. Understanding an expression for the relaxation time spectrum of polymeric and complex materials is advantageous for two reasons: first, it produces quantitative analytical expressions for the material functions, and second, it makes describing the linear viscoelastic behavior of any complex material simpler by requiring the determination of only a small number of material-specific parameters [27]. Our intention here is to provide a foundational framework of the effects of EG production methods on their rheological and textural characteristics and to discuss recent findings from a number of studies.