Polysaccharide-Based Fat Replacers in the Functional Food Products

Abstract

The functional properties of food products, in addition to enrichment with functional components, can also be achieved by reducing the content of certain components such as sugars and fats, that is, by reducing the energy content of the product. Thus, the development of functional food products is aimed at various low-energy products, especially products with a reduced fat content, which normally represent the most concentrated source of energy. Fat replacers should simulate the functional properties of the fat. Polysaccharide-based fat replacers include a variety of native starches, modified starches, maltodextrins, cellulose and cellulose derivatives, polydextrose, inulin, pectin, other dietary fibers, and hydrocolloids. Technological properties required for the application of carbohydrate-based fat replacers are water-holding capacity, a certain level of viscosity, required form and particle size, three-dimensional networking and gel-forming ability, sensory abilities such as spreadability, softness, greasiness feeling in the mouth, and other fat-like properties. These fat replacers are usually applied in combinations with the aim of achieving all desired properties normally provided by fats in foods. In the contemporary literature, there are many examples of their application in different food products, including baked goods, meats, dairy products, and emulsion food systems, successfully reducing the fat content with or without minor alterations in the rheology or sensory features of food products. In summary, polysaccharides-based fat replacers offer an effective method for fat reduction in different food products along with enhancing the health benefits of reduced-fat foods.

1. Introduction

Functional food, in addition to its usual nutritional function, has a beneficial effect on human health. It contains biologically active compounds that have a positive effect on certain functions in the body. The beneficial effect on health is manifested during continuous consumption of the usual amount of such food. Functional food has an optimal effect on the digestive system, immunity, and blood vessels and usually has a large antioxidant potential important in the fight against free radicals that are formed daily in human organisms [1,2,3].

Functional food contains one or more biologically active components. Those can be macronutrients (e.g., omega-3 fatty acids), micronutrients (vitamins or minerals), phytochemicals (isoflavones or phytoestrogens), or living organisms (probiotics). Biologically active compounds act at the point of release, such as dietary fiber and probiotics in the digestive tract, or have an effect on a certain biochemical function in an organism and thus improve the functions of a certain organ, organ systems, or whole organism [4].

In addition to the enrichment by some of the functional components, functional properties of food products can also be achieved by reducing the contents of components such as sugars and fats, i.e., by reducing the energy content of food products. This reduces the intake of components that can increase the risk of developing cardiovascular diseases, increase the level of LDL cholesterol in the blood, and reduce the development of diabetes and the contemporary problem of obesity [4,5,6].

Fat normally represents the most concentrated source of energy in food products; therefore, the development of functional food products is directed to different low-energy products, especially products with a reduced fat content.

The aim of this review is to present the origin and main characteristics of polysaccharides that have the ability to be applied as fat replacers and the trends of their application in different food products. The application of such fat replacers contributes to the functional properties of developed low-fat food products, along with many other beneficial effects caused by the dietary fiber nature of polysaccharides to human health.

2. Fat Replacers

The chemical composition of fat replacers can be similar to lipids, proteins, or carbohydrates, and in this sense, they are divided into two groups: fat substitutes and fat mimetics.

Fat substitutes are macromolecules with physical and chemical characteristics similar to triglycerides (fats and oils), and they can replace fat in food on a one-to-one basis. Because they are lipid-based, fat replacers can be obtained by chemical synthesis or enzymatic modification of fats and oils. They are mostly stable at baking and cooking temperatures, and their energy value is less than 9 kcal/g [7,8].

Fat mimetics are compounds that mimic the physical or sensory properties of triglycerides but cannot replace them on a one-to-one basis. Fat mimetics are based on proteins or carbohydrates and are common food ingredients (e.g., cellulose or starch) that may be previously physically or chemically modified to achieve the function of fat. The energy value of fat mimetics varies from 0–4 kcal/g. They have the ability to bind a large amount of water, which provides an appropriate feeling in the mouth, spreadability, and other desired characteristics. They are not suitable for use in food products that are thermally processed by baking or cooking because they are easily denatured or caramelized at high temperatures; however, there are also some thermostable fat mimetics [8,9], such as modified types of maltodextrins, starch, and cellulose. These fat mimetics are modified or prepared by special methods with the aim of achieving adequate thermostability. For example, the sweet potato starch-based fat mimetics prepared by energy-gathered ultrasound combined with enzymatic hydrolysis show good thermal stability, and the thermal disintegration temperature is up to 262.5 °C [10].

Protein-based fat mimetics are stable in moderately high temperatures [11], while fat-based (Olestra) or synthetic fat mimetics (Salatrim, Caprenin, and Esterified Propoxylated Glycerols (EPGs)) exhibit excellent thermostability and are used in applications requiring high-heat processing, such as frying or extrusion; however, regulatory considerations may limit their use [12,13]. Polymer oleogels are also relatively thermostable, which allows for controlling the melting temperature of some food products (e.g., bake-stable shortenings) [14].

A component that could completely replace fat in food systems should have all the functional characteristics of lipids but should be resistant to hydrolysis by digestive enzymes to have zero or very low caloric value. Fat replacers should simulate functional properties of the fat, such as sensory properties (smell and taste), rheological properties (viscosity, consistency, and texture), emulsifying properties, thermostability, and ability to dissolve liposoluble flavors and vitamins. An “ideal” fat replacer should mimic all the functional characteristics of fat while having a significantly lower energy value, preferably 0 kcal/g [15,16].

Rheological characteristics doubtlessly play an important role in the sensory perception of food. The adjustment of rheological properties plays a key role in the application of a suitable fat replacer in order to imitate the physical and chemical characteristics of fat. The complexity of a certain food product and its quality parameters significantly influence the possibilities of affecting the rheological characteristics.

However, the major problem with the application of fat replacers is achieving the appropriate sensory properties of a low-energy product. Many of these products have proven to be unacceptable to consumers in terms of product taste as its most important sensory characteristic. Figure 1 shows fat replacer classification, as well as food products in which they are used, according to adequate references [15,16,17].

3. Polysaccharides-Based Fat Replacers

Polysaccharides-based fat replacers include a variety of native starch, modified starch, maltodextrins, cellulose and cellulose derivatives, polydextrose, inulin, pectin, other dietary fibers, and hydrocolloid gums [18]. The main sources of these fat replacers are fruits, vegetables, legumes, grains, and seeds. They have a high water-binding capacity, so they are able to imitate some functional and textural characteristics of fat. There is no single fat replacer that is capable of imitating all desired sensory and functional properties of fat. Thus, a combination of fat replacers is usually used to achieve adequate quality of low-fat food products [19,20].

3.1. Technological Properties of Polysaccharide-Based Fat Replacers

Considering that polysaccharide-based fat replacers are also dietary fibers, a lot of significant technological characteristics affect the possibilities of their application.

Water holding capacity (WHC) is one of the most important properties. Soluble fibers, such as pectins and gums, have a greater water-binding and holding capacity than cellulose. The length and the density of the fibers have a strong influence on this feature, as well as the pH of the environment, which affects the water retention capacity [7,8].

Fat-binding capacity is an important physicochemical characteristic of polysaccharide-based fat replacers. This feature is primarily related to the microstructure of the fat replacer and not molecular affinity [7,8,19].

The viscosity is dependent on the nature of the polysaccharide-based fat replacer. Pectins, gums, and β-glucans can form high-viscosity solutions, while others, such as inulin, have minimal viscosity [19,20].

Gel-forming ability is the most important property in the application of polysaccharide-based fat replacers because gel structure should imitate the soft, spreadable structure of fats. The cross-linking of polymer units, simultaneously with the retention and incorporation of water or a solvent, creates a specific gel structure. Several factors, such as concentration, temperature, pH of the medium, and the presence of certain ions, affect to possibility of gel formation and its characteristics [20,21,22]. Figure 2 presents examples of the application of polysaccharide-based fat replacers in certain food products, according to the following references [19,20,23].

3.2. Starch and Starch Derivatives as Fat Replacers

Starch is a carbohydrate macromolecule obtained by polymerization of glucose molecules. Glucose units are covalently linked, forming linear macromolecule fraction of amylose and branched fraction of amylopectin. Amylose and amylopectin are composed of starch granules through a specific structure consisting of concentric crystalline and amorphous regions. Starch granules have a complex hierarchical structure. Starches from different sources vary in their ratio of amylose to amylopectin, which leads to differences in their functional characteristics [24,25]. Starch granules, during heating in excess water, undergo an irreversible phase transition known as gelatinization, where highly ordered structures are destroyed. During the gelation of starch granules there are at least three phases in the process. First, starch granules absorb water and swell. After reaching the maximum swelling capacity, starch granules lose their crystallization order, and their rupture is followed by a leaking of molecules, forming a starch paste [26]. During the cooling of a gelatinized starch solution, the released amylose molecules interact with each other by hydrogen bonds in a process known as starch retrogradation that leads to the creation of starch hydrogels [27,28]. The retrogradation process is strongly dependent on the initial concentration of starch. With a low initial starch dispersion concentration (1% w/w), a precipitate is formed after heating and cooling, while a higher initial starch dispersion concentration (5% w/w) results in the formation of a hydrogel [29]. Another key factor that influences the gelation process is the amylose content in the starch paste [26], as well as the length of the amylose chains. Amylose chains with a degree of polymerization (DP) < 110 precipitate from aqueous solutions at all temperatures, while the amylose chains with DP 250–660 precipitate or form gels, depending on the concentration and temperature. Amylose with DP > 1100 primarily forms gels rather than precipitate [29]. Thus, the primary formation mechanism of starch hydrogels is the entanglement and ordering of amylose molecules.

Starch-based fat replacers have many advantages, such as availability, renewability, and low price, which have attracted wide attention. Starch globules have similar sizes and shapes as fat globules and effectively imitate fat. Additionally, both native and modified starches exhibited specific physicochemical properties, such as thickening, bulking, viscous flow, water retention, and gel formation. These features enable them to mimic fat by stabilizing added water in a gel-like matrix and to provide similar sensory and physicochemical characteristics that are normally provided by fat; however, the use of native starch is limited by its fragile structure, insufficient thermal and pH stability, and rapid retrogradation, which reduce its functionality in certain food processing conditions, such as applications with low pH, high temperatures, or freezing conditions. To overcome these limitations, modified starch is used instead. Modification achieved through chemical, physical, or enzymatic treatments enhances the functional properties of starch [30,31].

Starch-based fat replacers are extensively used in a variety of food products, such as baked products, dairy products, salad dressings, and mayonnaise. These fat replacers have demonstrated significant effectiveness in reducing fat content over decades of research while maintaining product quality and without safety issues because they are generally considered safe [31].

Native oat starch has been shown to effectively replace up to 75% of the oil content in mayonnaise while enhancing stability and improving rheological properties. An additional conclusion in this research was that the native oat starch was as good as annealed starch in terms of the mayonnaise properties and stability. Furthermore, incorporating both native or annealed oat starches provides a clean-label product in addition to a lower-calorie, healthier food product [32].

Similarly, modified arrowroot starch has also been analyzed as a fat replacer in mayonnaise. Arrowroot starch was modified by various methods, using octenyl succinic anhydride (OSA), annealing (ANN), citric acid hydrolysis (CA), acetylation (ACT), and heat moisture treatment (HMT). These modified starch pastes were used to replace 30% and 50% of the fat content in mayonnaise. Each modification method altered the physicochemical, thermal, and pasting properties of different starch pastes, which in turn significantly influenced the quality of the mayonnaise. The types of modified starch pastes, ANN-, OSA-, and CA-modified starches, were found to be the most effective fat replacers in mayonnaise [33].

The crosslinked modified starches have the advantage of maintaining viscosity by forming a non-fat solid component that mimics the characteristics of fat. Additionally, their ability to retain water results in stable viscosity while contributing to a neutral taste and creamy texture that does not alter the final product’s flavor. In general, the crosslinking of starch can be enhanced through dual modification, such as combining cross-linking with oxidation to improve product characteristics. This method reduces the starch’s tendency to retrograde, ensuring that the starch granules retain a good three-dimensional network and improve the water-binding capacity compared with native starch. In addition, this starch can be used or mixed in products as a fat replacer, providing an impression similar to fat trough the increase in viscosity; however, the creamy sensation may be poor, and the non-fat solid phase tends to be difficult to swallow [34]. The crosslinked starch and dual-modified crosslinked starch can be used in many foods, such as low-fat creams, low-fat ice creams, low-fat mayonnaise, muffins, pork meat, and processed meats [26,35,36]. Different sources of starch can be used for starch modification, such as corn, rice, sweet potato starch, and cassava starch.

Another type of modification frequently used for the production of starch-based fat replacers is acetylation. During acetylation, some of the anhydroglucose units in starch, which are extremely hydrophilic hydroxyl groups, are replaced with more hydrophobic acetyl groups. This reaction is facile, non-toxic, and renewable, and the by-products are easily washed and purified. Acetylated starch exhibits enhanced solubility, swelling power, and water absorption, making it a useful functional ingredient in a variety of food products, including confectionery, dairy products, baked goods, salad dressings, and various meat products, such as low-fat patties, low-fat bologna sausages, and other processed meat products [37].

The esterification of starch granules with octenyl succinic anhydride (OSA) replaces its hydroxyl groups with hydrophobic groups, providing amphiphilic and interfacial properties to starch. This type of modified starch is known as octenyl succinic anhydride (OSA) starch [38]. The esterification reaction in OSA synthesis usually requires pre-treatment methods, such as mechanical, ultrasonic, hydrothermal treatment, or acid and enzymatic hydrolysis, to optimize the reaction. OSA starch is a cheap, fat-free ingredient that exhibits excellent paste and emulsion formation properties, making it a suitable fat replacer in various food products [38]. Additionally, OSA starch has functional health benefits, such as slow digestibility, which makes it a promising ingredient for developing reduced-fat functional food products, such as mayonnaise, salad dressings, cookies, muffins, and some bakery products, according to recent studies [33,38,39,40].

Physically modified starch is applicable as a fat replacer in some instant food products, which require instant hydration or mechanical action, such as dairy-based products, commonly used as primary ingredients in ice creams and as toppings and fillers in bakery products. For example, retrograded and retrograded-annealed rice starches can be used for partial replacing of fat in whipping cream. Reduced-fat whipping cream is obtained with up to 62% less fat than commercial versions. The cream texture of a reduced-fat product was closest to the commercial standard, with improved whipping ability and foam stability. This suggested that the dual physically modified starches, retrograded-annealed starch, provide an effective and thermostable alternative to fat in whipped cream, with the added benefit of controlled glucose release [41].

Many starch derivatives, obtained by the decomposition of starch, for example, by starch hydrolysis, are able to accomplish the fat replacer role. Maltodextrins are products of starch hydrolysis with a dextrose equivalent (DE) value ranging from 0 to 20. The physicochemical properties of maltodextrins vary depending on their specific DE value. Maltodextrins with lower DE values are characterized by a high amount of long oligomer chains, which tend to interact between amylose fractions and branched amylopectin molecules, resulting in the formation of a three-dimensional network and the ability to form weak gels [42]. Maltodextrin aggregates, with irregular shapes, are from 3 to 5 μm in diameter, which is very similar to fat crystal particles. This similarity contributes to their fat-like behavior, providing fat-like texture in low-fat foods [31,42]. Interestingly, the maltodextrin gel consists of just one part maltodextrin and three parts water molecules, which results in a significant reduction in energy content, from 9 kcal/g to 1 kcal/g, in food products [31]. Maltodextrin gels have a wide range of technological functionalities, such as flow properties, lubrication, and creaminess (gels), and can be easily combined with liquid and solid fats and form a stable emulsion gel, which gives the same taste as fat since it helps foods to be broken easily into pieces in the mouth [43]. They are especially applicable as fat replacers in low-fat dairy products such as yogurt, cheese [44,45], low-fat or reduced-calorie ice cream [46], and baked products [47].

Starch-based fat replacers can also be a part of the new generation of fat replacers known as starch-based emulsions and starch-based structured gels [25]. The emulsion gel is an emulsion with a gel-like network structure exhibiting a solid-like texture [48]. This viscoelastic colloidal product transforms liquid oil into a semi-solid state, combining the beneficial properties of both biopolymer hydrogels and emulsions. A highly elastic starch-based emulsion gel can be formed through one-step heat-set gelation of an emulsion stabilized by octenyl succinate starch. This gel can be used in food structuring and as a fat replacer [49]. The stability and some important properties of starch-based emulsion gel systems can be enhanced through physical interactions during complexation with other biopolymers, such as sodium alginate [50] or proteins [51]. These gels effectively replace animal fat while maintaining the physical and chemical properties, especially the stiffness and water-holding capacity of the final product [51].

Starch can be included in fat replacer systems known as hybrid gels or bigels. Bigels are binary systems and a viscoelastic semi-solid structure composed of oleogels and hydrogels. The hydrogel phase in a bigel system can be built from wheat starch, whereas sunflower oil and ethylcellulose build the oleogel phase. This bigel can achieve a fat content reduction of up to 50% in model meat products [25]. Potato starch hydrogel was also used for the formation of bigel in combination with glycerol monostearate, which produces the oleogel phase. A previous study found that the structural properties of a bigel were significantly influenced by the oleogel and hydrogel ratio. The improved thermal stability, softer texture, more crystalline system, lower viscosity, and good plasticity and spreadability were achieved with an increase in the oleogel phase, while a higher proportion of the hydrogel phase should be added in the aim to have firmer gel [52]. Further research [53,54] demonstrated the potential use of hybrid gels, made of canola oil—candelilla wax oleogel and gelatinized corn starch hydrogel, as a shortening replacer in cookie production. This combination of oleogel and pregelatinized starch helps reduce fat content while maintaining the textural properties of full-fat cookies. This study indicated that replacing part of the commercial shortening with this hybrid gel in sugar-snap cookies could reduce total fat and saturated fat by up to 50%.

3.3. Cellulose and Cellulose Derivatives as Fat Replacers

Cellulose is a high molecular linear homopolysaccharide composed of glucopyranose units (300–15,000) connected by β (1–4) glycosidic bonds. As a consequence of the existence of supramolecular structure, the structure of cellulose is a combination of crystalline and amorphous regions. The crystalline regions represent strictly ordered structures with a linear arrangement of cellulose chains, while the amorphous regions are rather disordered and with irregular cellulose chain orientations [8,16].

Cellulose is not soluble in water because of a large number of intra- and intermolecular hydrogen bonds that keep it in a crystalline form in an aqueous solution. Cellulose needs to be transformed into soluble forms for use in the food industry, usually by derivatization process, during which hydrogen bonds break up. Each of the three OH groups of the glucose unit is available for reaction, which means that the polymer has a maximum degree of substitution of three. The degree of substitution determines the average number of substituted OH-groups of the cellulose unit within the cellulose molecule. By controlling the degree and type of substitution, a large number of cellulose derivatives can be obtained [16]. Cellulose and its derivatives are considered promising natural fat replacers due to their functional properties that help to maintain the stability and sensory qualities of food, such as emulsifying activity, water-holding capacity, and gelation ability. Since cellulase is absent in the human gastrointestinal tract, cellulose is indigestible and cannot be absorbed, making it a zero-calorie dietary fiber intake by humans. Moreover, cellulosic materials can enhance satiety and reduce the degree of lipid digestion, providing potential health benefits in food products [55].

In the food industry, the most used are carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropylmethyl cellulose (HPMC), and hydroxypropyl cellulose (HPC) because they have good hydrocolloid properties. Various modifications of cellulose are also used in the food industry, primarily cellulose powder and microcrystalline cellulose (MCC). The properties and applications of microcrystalline cellulose (MCC) are influenced by the depolymerization process, particle size, and moisture content [7,8,16]. The cellulose derivatives can be used in reduced-fat meat products. For example, different cellulose derivatives were used as fat replacers in meat butter, but with distinct variations in their specific properties [56]. Methyl cellulose (MC) specifically showed some inconsistencies during the heating and cooling of meat batters, which resulted in elevated cooking loss compared with the control samples. Carboxymethylcellulose (CMC) disrupted the meat batter matrix at the microstructural level, resulting in reduced textural hardness compared with the control samples. In contrast, microcrystalline cellulose (MCC) demonstrated cooking loss and textural hardness levels compared with the control samples, suggesting it may be the most promising option in this study [56].

Microcrystalline cellulose (MCC) also realized the role of fat replacer in emulsions, mayonnaise, gravies and sauces, bakery products, and frozen desserts. MCC provides a rich, creamy texture in low-fat sauces and dressings because of its insolubility and ability to mimic the mouthfeel of fat [57].

Different cellulose ether emulsions, such as hydroxypropyl methylcellulose, methylcellulose, and methylcellulose with greater methoxyl substitution, can be applied as an effective fat replacer in biscuits. These emulsions made with cellulose ethers provide an excellent way to reduce fat content in biscuits while maintaining similar technological characteristics to the control dough. Additionally, biscuits prepared using these emulsions were well-received by consumers, making them a viable option for creating reduced-fat biscuits without compromising on texture and acceptability. Hydroxypropyl methylcellulose and methylcellulose caused the increased hardness of biscuits, while this effect was not obvious for methylcellulose with greater methoxyl substitution (MCH) emulsion [58].

The natural structural characteristics of cellulose influence its functional properties as a fat replacer. The modification of cellulosic materials into nano-sizes can improve the properties of the particles observed from physical perspectives, including particle size and morphology, chemical interactions with other food ingredients, and biological properties such as prebiotic efficiency [55]. Cellulose nanomaterials such as nanocrystalline celluloses (NCCs) and nanofibrillated celluloses (NFCs) have effective WHC and gelation ability thanks to abundant presence of hydroxyl groups and can be used as fat replacers singly or in combination with other hydrocolloids. In the reduced-fat mayonnaise or dressings, the NFCs achieve the formation of a three-dimensional network with a gel-like, viscoelastic structure that can prevent droplet aggregation while controlling the desired rheological and textural properties. The synergistic interaction between nanofibrillated celluloses (NFCs) and certain polysaccharides, such as guar gum, carboxymethylcellulose, and galactomannan, can enhance the colloidal stability and rheological properties of emulsion systems. The sources for nanofibrillated cellulose can differ between agricultural wastes. Nanofibrillated cellulose from grapefruit peel (GNFC) was used as a fat replacer in ice cream, achieving a maximum fat reduction of 17.90%. With 0.4% GNFC addition this fat replacement resulted in a desirable elastic-dominated behavior and good textural properties, with an optimal three-dimensional network structure. The sensory evaluation of the fat-reduced ice cream showed the highest acceptance [55,59].

Cellulose takes part in some complex systems, such as protein emulsion-based fat replacers. The protein-based emulsions are effective oil-based systems for fat replacement due to their excellent nutritional value, emulsifying and gelling properties, and interfacial stability. The addition of cellulose enhances the nutritional profile, texture, and sensory properties of these emulsions. This improvement is attributable to cellulose’s ability to retain water, stabilize interfaces and networks, and provide a thickening effect, as well as cellulose’s contribution to nutritional value via an increase in dietary fiber content [60].

Ethyl cellulose (EC) is valued for its distinctive physical and chemical properties, making it suitable for various food applications. It has high flexibility, thermoplasticity, significant mechanical strength, excellent film-forming ability, and transparency, which are beneficial for coating applications in different products. Due to its hydrophobic nature, EC is compatible with organic materials and can act as a rheology modifier in films and binders. Additionally, it is tasteless, odorless, non-caloric, and physiologically inert [61]. Ethylcellulose forms a gel when heated in mediums, oil, or water-in-oil (W/O) emulsions. During heating, its molecular chains become more flexible and interact more extensively, leading to the creation of a gel-like network [62]. When ethylcellulose is dissolved in oils, the viscosity increases, and this property is temperature-dependent. Higher temperatures enhance both the solubility and gel strength of the polymer, allowing for better gel formation and stronger network development [63,64].

The EC powder is mixed with oil in order to achieve the gelation of oil by ethyl cellulose (EC). The mixture is heated above the glass transition temperature (approximately 140 °C) of EC and then cooled to room temperature. The properties of EC/oil gels can be modified by adjusting the polymer’s molecular weight and concentration, selecting different oils, varying the heating and cooling profiles during preparation, or adding small surface-active molecules. The specific characteristics of EC gels make them suitable for a wide range of applications, including food, pharmaceuticals, and biomedical fields [60,65,66].

EC oleogels are considered a promising alternative to replace fats in various food products, including meat products such as frankfurters, breakfast sausages, cooked meat batters, and meat emulsions [48], margarine and shortening products [67], cream fillings, chocolate formulations, cookies and confectionery products [61].

The factors that influence the mechanical properties of EC oleogels are the setting temperature during gelation, post-gelation thermal treatment, and the stability of the gels over time. Between gel strength and the temperature at which the gel sets there is a relationship in a term that higher setting temperatures lead to increased gel strength because of the enhanced ability of EC polymer chains to form hydrogen bonds. At lower setting temperatures, polymer chains associate rapidly, forming less ordered hydrogen bonds. Higher temperatures allow slower, more ordered cross-linking, resulting in a stronger network. This indicates that increased gelation temperatures improve the polymer’s ability to form junction zones, resulting in the observed differences in the mechanical properties of the gels [65,66].

The gelation process in thermo-reversible gels is defined by the time scale in which these processes take place. Slow cooling results in the formation of a more stable and organized structure, whereas rapid cooling leads to varying dynamic states, which cause the creation of a wide range of thermal memory effects [68]. Thus, the viscosity of the EC-based oleogels decreases with an increase in temperature, and more solid-like aspects are formed at the lowest temperature (25 °C) and liquid-like at the highest temperature (37 °C). This characteristic is useful in food formulations that require specific textural modifications [69]. The nature of the EC gel network, characterized by physical crosslinks formed through hydrogen bonds, appears to induce non-equilibrium behavior in these gels. This behavior explains the observed temperature effects and temperature memory characteristics [65].

Ethyl cellulose (EC) and hydroxypropyl methylcellulose (HPMC) achieve the role of oleogelators in the preparation of olegels with pure sunflower oil or blends of sunflower oil and palm stearin [70]. Many types of olegels include cellulose ether as oleogelators. Sunflower oil-cellulose-based oleogels can effectively replace shortening in croissants by up to 100% without significantly compromising their textural properties. This substitution of solid conventional fats with structured vegetable oils presents a promising approach to reducing the consumption of saturated and trans fats in puff pastry bakery products while preserving the functional and sensory qualities typically provided by hard stock lipids [71].

Ethylcellulose, which is used as an oleogelator in sunflower oil-based oleogels, can also be combined with wheat starch (a hydrogelator) to create a novel food-grade bigel system as s potential fat replacer in food products. Bigels are formulated by physically mixing hydrogel and oleogel phases in varying hydrogel: oleogel mass ratios. Results show that the mechanical properties and structural stability of the bigels are primarily influenced by the oleogel fraction. Rheological analyses demonstrate gel-like behavior even at high temperatures, indicating strong thermal stability. Thus, obtained bigels showed good potential for the replacement of fat in meat products that require thermal treatment [72].

The hybrid of a polypeptide polymer, gelatin, with CMC as a polysaccharide in the hydrogel phase of the bigel structure, is a way to create a novel hydrophilic matrix for different purposes [73].

3.4. Polydextrose

Polydextrose is a source of soluble dietary fiber applicable in foods and beverages. It is a synthetic carbohydrate derived from glucose and sorbitol in the presence of citric acid. Polydextrose is classified as a “carbohydrate” by the FDA because it is a non-digestible polysaccharide with randomly cross-linked glucose, which provides only 1 kcal/g of energy. Its excellent processing properties and potential health benefits make it a widely used low-calorie bulking agent for partially replacing fats and sugars in various foods. Polydextrose is an odorless white-to-cream amorphous powder with a neutral taste. It is highly soluble in water, dissolving up to 80% w/w at 20 °C. This enables polydextrose to provide the desirable mouthfeel and textural qualities when replacing sugars and fats. Polydextrose exhibits fat-like plasticizing effects by retaining moisture, making it suitable for bakery products (e.g., layer cakes), confections (e.g., soft candies), and frozen desserts (e.g., ice cream) that require soft, melting textures [74,75]. Additionally, it forms a viscous gel-like matrix, contributing to a creamy mouthfeel, and is commonly used as a fat replacer in low-fat dairy products. The effects of incorporating polydextrose at different concentrations (1.5%, 3%, and 5%) as a fat replacer on the physicochemical, sensory, and rheological properties of fat-free buffalo yogurt have also been studied. The findings revealed that polydextrose could serve as both a fat replacer and a prebiotic material, enhancing the quality attributes of fat-free buffalo yogurt. A minimum concentration of 3% significantly improved water-holding capacity (WHC), texture, and sensory properties of yogurt [76,77].

In shortcrust pastry, the fat content can be reduced up to 50% with the addition of polydextrose while maintaining the texture normally associated with traditional full-fat pastry [74]. Polydextrose is also used as a low-calorie fat replacer and bulking agent in butter [78].

Polydextrose can also be used in combination with other ingredients and used as a fat replacer. In combination with guar gum can be used as a fat replacer in rice cookies. This substitution effectively reduced the fat content by 27.86% compared with the control formulation and significantly influenced their physical, chemical, textural, and sensory properties. These findings suggest that polydextrose and guar gum are good alternatives for reducing the fat content in bakery products, highlighting the potential for using various ingredients to develop reduced-fat alternatives [79]. For example, two types of fat replacers, polydextrose and whey protein concentrate, were used to replace 10–50% of the fat content in multigrain biscuits. Based on sensory and physicochemical analyses, replacing 40% of shortening with an equal proportion of polydextrose and whey protein concentrate produced the most optimal results [80].

3.5. Inulin

Inulin is a type of fructan polysaccharide, a water-soluble carbohydrate that is non-digestible. It is composed of a mixture of linear fructose polymers of varying chain lengths, each terminating with a glucose molecule at the C2 position and linked through β-(2-1)-D-fructosyl-fructose bonds [81]. It is widely used in the food industry and applied either alone or combined with other ingredients to create innovative, functional food products. It serves as a low-calorie sweetener, fat replacer, gelling agent, viscosity modifier, texture enhancer, non-digestible fiber, and prebiotic [82]. Inulin forms a smooth gel in an aqueous system during vigorous mixing, followed by cooling. Obtained gel can enhance creaminess and juiciness in various food products. This makes it an effective fat replacer that provides a fat-like mouthfeel without altering rheological properties. For example, inulin has been incorporated into low-fat meat products to reduce calorie content to approximately 1–1.5 kcal/g [82,83]. In chicken sausages, water-based inulin gels prepared with garlic inulin reduced the fat content from 13.67% (control) to 4.47–4.85% when added at 3%. Additionally, 2% garlic inulin improved sensory attributes such as flavor and overall acceptability, making it a suitable fat replacer without compromising meat quality [83]. In low-fat Bologna sausages, an inulin-based gelled emulsion with soybean oil replaced animal fat, achieving a 31% fat reduction compared with the control samples [84]. The meat product obtained reached the standards necessary for being labeled as reduced in saturated fat and as a good source of fiber. Similarly, inulin used in reduced-fat burgers demonstrated its ability to replace 15% fat with 10–15% inulin or a combination of 15% inulin and 5% fat, with no significant impact on sensory or texture properties of reduced-fat meat burgers [85].

Many studies provide evidence that inulin is a promising and effective fat replacer in baked products, which can help to create low-fat, low-calorie food products with excellent functional properties and nutritional value. Its potential as a fat replacer in low-fat muffins has been investigated, revealing that adding 15% inulin reduced the fat content by 68.05% and calories by 12.63% compared with the control sample without significantly impacting the physicochemical properties or sensory acceptability of muffins. Additionally, inulin increased fiber content by 82.76% compared with the control and enhanced the muffins’ height and aerated structure [86]. Furthermore, the addition of inulin at 8% and HPMC at 0.2% as fat replacers in low-fat muffins resulted in acceptable quality parameters that were comparable to the full-fat version. Inulin improved various muffin characteristics, including batter viscosity, texture hardness, and resistance to retrogradation [87].

An emulsion-filled gel made from inulin and extra virgin olive oil can serve as an effective fat replacer in shortbread cookies. Substituting 40% of the butter with this ingredient enables the product to qualify for the health claim “reduced saturated fat content” [88]. Other low-fat food products are developed thanks to inulin addition, such as the low-fat pea protein vegan ice cream with prebiotic properties [89], Tamales—a traditional dish rich in fat and carbohydrates [90], low-fat margarine [91], low-fat yogurt [92] and others.

3.6. Pectin

Pectin is a biopolymer and a type of pectic polysaccharide-based structural fiber derived from the primary cell walls and intracellular layers of higher plants, particularly fruits such as apples, oranges, lemons, etc. [93,94]. It consists of a backbone of α-(1–4)-linked polygalacturonic acid, containing 300–1000 galacturonic acid units. In its natural form, many of the acid groups along the chain are esterified with methoxy groups, and there can also be present acetyl groups on the free hydroxy groups. The degree of methyl esterification (DM) of pectin ranges from 0% to 100%, which determines its classification into two types: high methoxy pectin (HMP), with DM > 50%, and low methoxy pectin (LMP), with DM < 50%. The degree of methyl esterification significantly influences the gelling ability and properties of pectin [94,95,96,97].

Pectin is predominantly extracted on an industrial scale from apple pomace (14%), beetroot (1%), and citrus peel (85%). Recent research has shown that pectin can also be recovered from various by-products of the food industry, providing an opportunity to valorize agro-industrial waste [93]. The source of pectin and the extraction method significantly affect its structural and functional properties, such as viscosity and gelling ability, influencing its applications in the food industry. The valuable functional properties of pectin provide its application as a thickening agent, gelling agent, texturizer, emulsifier, stabilizer, and fat or sugar replacer. Its major use is based on its exceptional gelling properties [94]. Pectin is approved for use in food products worldwide, and the FAO/WHO committee recommends an acceptable daily intake of pectin without limitation as a safe additive, except where it is specified by good manufacturing practice [94].

Pectin hydrogels are widely utilized because of their soft and flexible nature, high water content, unique structure, intrinsic biocompatibility, and similarity to natural materials. While calcium-gelled pectin was initially considered suitable as a fat replacer, research has since demonstrated that covalently cross-linked pectin can also effectively behave as a fat replacer [98]. The ability of pectin gel to act as a fat replacer lies in its capacity to mimic the mouthfeel of fats by increasing the viscosity of the liquid phase in the mouth. The tangly interactions between the three-dimensional structure of the pectin gel and oil droplets may contribute to increased viscosity. The particle size of fat mimetics is very important. The particle size of the pectin gel, similar to that of the oil granules, provides a better fat replacer [99]. Additionally, microgel particles are identical to fat particles, considering their softness and deformability, and hence mimic the physical and sensory properties of emulsified fat [93].

Recent studies have highlighted the potential of using pectin as a fat replacer. For example, banana peel as a source of pectin has been investigated as a partial fat replacement in muffins, offering an alternative for reducing the fat content in bakery products. The incorporation of pectin not only improves the health profile by lowering fat content but also provides potential health benefits because of its dietary fiber content. Additionally, it demonstrates the feasibility of utilizing food by-products to enhance the nutritional value of food products, in line with sustainable food practices [96]. Extracted pectin has also been used as a butter substitute in cookies, where it successfully replaced up to 30% of the butter without altering the sensory or physicochemical properties of the final product. Overall, these findings suggest that using waste-derived pectin as a fat replacer in cookies presents a sustainable, health-promoting strategy that covert waste into valuable ingredients [100,101]. Generally, the extraction of pectin from fruit waste, such as unripe banana peels [96], avocado purée [102], citrus limetta peel [100], mandarin orange byproducts [103], or others and their application as a fat replacer in bakery products, such as cookies, biscuits, muffins proves the promising role of pectin as a fat replacer in bakery products, maintaining the quality of bakery products while addressing fruit waste challenges in the food industry.

Food waste sources of pectin have a good potential to be applied as fat replacers in other food products, such as salad cream or mayonnaise. Partial substitution of oil in salad cream with pectin from banana peels resulted in a darker color and reduced viscosity and rheological properties compared with the control sample but did not affect consumer acceptability. This suggests that banana peels can be a viable source of pectin, with the potential as a fat replacer in high-fat food products [104]. Pectin is also considered a promising alternative to animal fat in meat products. It is often used in combination with other biopolymers, such as pectin and inulin blends, to replace animal fat in emulsion-type sausages. A formulation containing 15% pectin and 15% inulin can replace animal fat without a negative influence on the chemical composition, texture, or sensory properties of emulsion-type sausages [94]. In addition, 5% of pectin from mango peel extracted by microwave-assisted extraction can be effectively used as a fat replacer in dried Chinese sausage [105].

3.7. Other Fibers and Hydrocolloids Gums

Fibers, gums, and their derivatives are commonly used as thickeners, emulsifiers, and textural enhancers in the food industry. The main types of gums approved for food applications include guar gum, locust bean gum, xanthan, carrageenan, and alginate. Additionally, various fibers not previously discussed in this review, such as different types of cereal brans and β-glucan, are also widely used [20,106,107]. An example of a fiber-based fat replacer is wheat fiber-based fat replacer (WFG), presented by the authors [108] as a good alternative to traditional fats in food products. This fat replacer was evaluated for its functional properties, including microstructure, rheological behavior, and texture properties. The study found that at concentrations above 3% of wheat fibers, hydrated wheat fibers form viscoelastic gels with a predominance of elastic properties that mimic the functional properties of fats. At higher wheat fiber concentrations (5–10%), the firmness and consistency of these gels were stable, making them promising for use as continuous-phase fat replacers in food systems. The findings underscore the potential of fibers from natural sources such as wheat to contribute to sustainable and low-energy food product development while highlighting challenges in integrating such replacers with different food additives. The addition of food additives, such as sodium ascorbate, trisodium citrate, and sodium acetate, disrupted hydration and gel formation, diminishing the mimetics’ performance [108]. The same effect of various additives on the performance of cellulose-based fat mimetics, specifically their rheological and textural properties, was also observed by the authors through the rheological and textural properties of cellulose-based fat mimetic (microcrystalline cellulose MCC coated with sodium carboxymethyl cellulose Na CMC [109,110]. The authors concluded that the addition of certain small molecules and hydrophilic additives influenced the gelation process and structural characteristics of the mimetic, disrupting the hydration process and reducing the ability of fat mimetic to imitate the texture and mouthfeel of fats effectively. Higher cellulose fiber concentrations enhanced crosslinking, resulting in stronger gels and improved consistency. Both of these works underscore the importance of balancing additive concentrations to optimize the functional performance of fat mimetics in food formulations.

Carbohydrate gums, also known as hydrocolloids, are commonly used as fat replacers in food formulations because of their ability to mimic the texture, mouthfeel, and stability provided by fats because of their high water binding capacity and water trapping [106,111]. The functional properties of polysaccharide hydrocolloids used in the food industry arise from their ability to enhance viscosity or thickness, to cause gelation, texturization, stabilization, and emulsification, water binding, oil and flavor binding, foaming, cohesion–adhesion, or to prevent ice-crystal formation, and sugar crystallization, among other effects [112].

Gums and fibers, as hydrocolloids, can form entanglements and cross-links with other food components such as proteins, starches, and emulsion droplets through hydrogen bonds. In addition, hydrophobic or electrostatic interactions can occur. These interactions contribute to the characteristic texture and mouthfeel of food products [18,20,44].

Most applied gums as fat replacers are plant-based gums, such as guar gum (from leguminous seeds), locust bean gum, carrageenan (red seaweed), or microbial-based gums, such as xanthan gum (from Xanthomonas campestris). They can be used in baked products, salad dressings, and sauces for thickening, providing mouthfeel, texturizing, retaining moisture, retarding staling [47,106,113,114]. Frequently used fiber as fat replacers are cereal fibers (from plant hull and bran, e.g., wheat, oat, soybeans, peas, corn, and rice) and β-glucan (from oat and barley). Their functional properties contribute to body consistency, smoothness, and mouthfeel, providing moistness and texturizing, usually achieved in bakery products, frozen desserts, confectionery products, spreads, cheese, hamburgers, etc. [115,116,117].

Gums and fibers are often combined with other fat replacers to achieve optimal performance in low-fat foods. For example, the specific mixtures of guar gum and xanthan gum or citrus fiber have been used to mimic the role of the oil emulsion and to produce low-fat mayonnaise with highly scored sensory properties very similar to its full-fat counterpart. Similar formulations with a blend of guar gum and basil seed gum have also been reported for low-fat ice cream, where the gum blend provided a creamier texture compared with using guar gum alone [20].

4. Conclusions

Polysaccharide-based fat replacers have many technological and functional properties required for the replacement of fat in reduced, low-fat, or non-fat food products. Such abilities of these types of fat replacers are usually naturally occurring, because of their origin from different plant-based sources and thus their dietary fibers nature. In addition, different types of modification can contribute to the functional properties of these fat replacers, that is the case with the application of modified starch, or different starch and cellulose derivatives.

Chemical structure and variety of chemical affinity and physical properties provide abilities to the polysaccharide-based fat replacers, such as water holding capacity, certain level of viscosity, required form and particle size, three-dimensional networking, and gel-forming ability, and many others which enable the imitation of functional properties of fat in food products, such as adequate rheology and texture properties, spreadability, softness, grease mouthfeel, and other fat-like properties. These fat replacers are either used individually or in combination because it is often difficult to simulate all of the required properties that are normally provided by fats in foods using a single ingredient.

Many polysaccharides are declared as dietary fibers; thus, additional beneficial properties of polysaccharide-based fat replacers are an increase in dietary fiber content in developed reduced-fat products.