An overview on the types, applications and health implications of fat replacers

Abstract

Driven by the demand of consumers for low-fat foods, the field of fat replacers has made a tremendous breakthrough over the past decade. A fat replacer is a substance that replaces whole or part of the fat in food while asserting the same physiological properties. Based on the source, fat replacers can be carbohydrate, protein or lipid-based. They serve two major purposes in food viz. reducing the calorie content and amount of fat used in the preparation of food products as well as impart fat-like properties. Fat replacers exhibit its functionalities by providing texture, acting as stabilizers, emulsifiers, gelling and thickening agents. It is crucial to select the proper kind of fat replacer because fat functionality varies considerably depending on the meal type and the formulation. Evidence suggests that reducing fat intake can help in controlling body weight and the risk of diseases like type-2 diabetes, hypertension and cardiovascular disease. Consumers should not be misled into believing that fat and calorie-reduced foods may be consumed indefinitely. Fat replacers are most beneficial when they aid in calorie control and promote the consumption of meals that provide essential nutrients. This review aims to provide a deep insight into the fact that fat replacers can be utilized in various food commodities in order to meet the dietary guidelines for reducing fat intake with a healthy lifestyle and prudent dietary approach.

Introduction

Consumers nowadays are more health-conscious and aware than ever before. They look forward for healthier alternatives and psychological satisfaction at the same time. Fat replacers are among such products which are designed to stimulate the functional and organoleptic properties of fat with a substantial reduction in calorific value (Omayma and Youssef 2007). Utilization of fat replacers aids in minimizing the quality deterioration that occurs due to the reduction of fats in food products. Moreover, it also helps in the development of low-calorie products such as butter, cheese, ice cream, potato chips, salad dressings and many more (Peng and Yao 2017). Emulsifiers or lipid analogues make up the majority of the fat substitutes as they provide far less calories since they are neither hydrolyzed nor absorbed by the body like normal fat (Omayma and Youssef 2007). According to current dietary standards, the total fat intake should be limited to 30% of calories, whereas saturated fat intake should be limited to 10% of the total energy intake. A high-fat diet may lead to excess energy intake and the genesis of obesity further leading to the origin of many diseases like diabetes, hypertension, high blood cholesterol and cardiovascular diseases due to which almost every dietary guideline developed by various organizations recommend restrictions on fat intake; however, people may not adhere to these recommendations (Omayma and Youssef 2007). The Dietary Guidelines (2015–2020) for Americans do not emphasize the restriction of total fat intake; however, it restricts the intake of trans-fat saturated fats, and recommends the consumption of low-fat or fat-free foods in order to establish a holistic approach towards healthy living. Nutritionists agree that one way to replace fats is by swapping high-fat food with low-fat food products such as fruits, veggies, and healthy grains like oats, barley or, jau. Other methods of replacing fat may include the use of skimmed milk instead of whole milk, the use of lean meats in frozen entrées (Hsu 2006) and traditional techniques like substituting air or water for fat. However, the presence of fat in food is preferred since it enhances emulsion qualities, acceptability, palatability, textural features, etc. As a result, utilizing fat replacers in diet is necessary to replace fat (Shelke 2016). These fat replacers can either be classified as carbohydrate-based, protein-based or fat-based, depending upon the source from where it is derived. For instance, taro-mucilage (a chief source of carbohydrates) is a potent fat replacer owing to its excellent functional properties such as binding, foaming, thickening, emulsifying, gel-forming and swelling capacity. Mucilage tends to swell and solubilize in aqueous system leading to the formation of viscous material that is similar to the functional characteristics of fats (Tosif et al. 2022). This comprehensive review aims to evaluate different fat replacers available in the market, their applications in various food products, health implications and the regulations governing its utilization.

Dietary fat and its harmful effects

Dietary fat is the major macronutrient in the human diet and is frequently overconsumed in developed countries such as America. It provides flavor, sensory qualities, mouthfeel, creaminess, palatability, satiety and other psychological benefits to the consumer. As an energy-dense dietary nutrient, fat provides 9 cal/g of energy upon consumption, which is twice that of carbohydrates and proteins (Peng and Yao 2017). Excess consumption of fat, is one of the most critical risk factors that contribute to a number of chronic diseases, such as cardiovascular diseases, type 2 diabetes, cancer, and obesity (Mozaffarian 2016). Obesity in itself is a challenging problem to treat ever since its emergence, so the primary prevention of weight gain is a promising strategy for individuals as well as the population. Owing to the detrimental health effects and economic repercussions of high dietary fat consumption, reduced-fat meals are a realistic and feasible option. FSSAI has also announced regulations to limit the content of trans-fat in food as research has shown that consuming large amount of industrially produced trans-fat is associated with an increased risk of high cholesterol and heart diseases. Under this regulation, FSSAI limited industrial TFA (trans-fatty acids) to not more than 3% in all fats and oils by January 2021 and not more than 2% by January 2022. It also stated that all food products in which edible oils and fats are used as an ingredient should not contain industrial TFA of more than 2% by mass of the total oils/fats present in the product, on and from January 1, 2022. With this India has joined the group of over 40 countries around the world that have already implemented policies to remove trans-fats. However, low-fat food can lack taste, mouthfeel and psychological properties which decreases the acceptability of food (Marchetti and Andrés 2021). To address this general problem, fat replacers are applied to compensate the loss of fat related properties and improve the overall acceptability of a low-fat diet (Peng and Yao 2017).

Fat replacers

Fat replacers are defined by the American Dietetic Association as “an ingredient that can be used to provide some or all of the functions of fat, yielding fewer calories than fat”. A wide range of products in the food industry uses fat replacers, major being meat, dairy and bakery and confectionery industry (Colla et al. 2018). The creation of low-fat and fat-free foods with the flavour and texture of high-fat foods has been made easier by the discovery of fat replacers (Jones and Jonnalagada 2006). The chemical composition of a fat replacer along with its activities in the food system, influence its performance. Sometimes fat replacers are combined with surplus ingredients like maltodextrin, polydextrose and guar gum to provide better fat-like qualities these extra ingredients are usually emulsifiers or fat replacers typically designed to supplement the undesirable effects of individual fat replacers (Colla et al. 2018).

Fat substitutes

Fat substitutes are usually produced by enzyme-modified oils and fats and can also be synthesized chemically (O’Sullivan 2016). They imitate the functional and sensory features of fat in food, and generally have no or fewer calories than conventional fats and are usually indigestible. They are also stable to cooking, baking and frying temperatures. Sugar or sugar alcohol fatty acid esters such as sucrose polyester (olestra), sorbitol polyester and raffinose polyester are among the most studied fat substitutes (Zheng et al. 2015).

Fat mimetics

Fat mimetics are generally protein or carbohydrate based and also possess different chemical structures from fat. These are substances that imitate the organoleptic or physical properties of triglycerides but cannot replace fat on a one-to-one or gram-for-gram basis (Solanke et al. 2016). Though fat mimetics have distinct microstructural and rheological properties than fat, when they are employed to substitute fat in food products, the end products have similar qualities to that of the normal formulation (Patel et al 2020). They have diverse functional properties that resemble some of the characteristic physiochemical attributes and desirable eating qualities of fat like viscosity, mouthfeel and appearance (Johnson 2008). They are also referred to as ‘texturizing agents’ and require a high water content to achieve their functionality. They provide lubricity, mouth feel, and other characteristics of fat by holding water which makes them unsuitable for fat functions (frying); however, some can be used for baking but at retort temperatures. In some cases, extreme heat may lead to excessive browning (Oreopoulou 2006).

Fat analogs

These are fat-like molecules with almost the same properties but lesser digestibility and even lower nutritional value. A single fat substitute cannot replicate all the physiological and sensory properties thus, leading to the creation of a combination of certain substances for a specific application (Omayma and Youssef 2007). Each formula is assessed for its overall energy value in addition, after the acceptability and long-term use of these reformulated goods have been established, the impact on energy intake is assessed again.

Carbohydrate based fat replacers

The functionality of carbohydrate-based fat replacers depends on two approaches. Primarily, they are macromolecules that impart fat depleted products with characteristic physicochemical and sensory properties like viscosity and thickness (Lim et al. 2010) and secondarily, carbohydrates naturally or by processing form micro particulates that resemble fat globules and emulsion droplets thus mimicking fats (Peng and Yao 2017). Starch-based fat replacers can be derived from common corn, high amylose corn, waxy maize, wheat, taro, potato and rice or plant organs such as the roots, leaves, tubers and seeds (Kunle 2019). Amylose and amylopectin are the two most important components of starch which get digested in the GI tract and provide ~ 4 cal/g of energy on average. Taro mucilage has been used as a fat replacer in the development of bakery products. It promotes moisture retention in low-fat foods and increase viscosity of the medium due to its excellent water-holding capacity. Thus, mucilage poses a positive impact on the rheology of food products (dough structure) and results in softer dough (Tosif et al. 2022).

Gums

Gums like guar, xanthan and locust bean gum have always been found safe to use in food products and serve as excellent fat replacers. Structurally gums do not resemble fats but due to their ability to form crosslinks and entanglement with starch and protein using hydrophobic or hydrogen bonds, they provide characteristic texture and mouthfeel (Ognean et al. 2006). Guar gum is specifically used in certain bakery products to decrease their fat content. Apart from this, it is also used in yogurt, ice cream, soups and sauces. It gives meat products a smooth creamy mouthfeel and is utilized in reducing fat reformulated meat products (Rather et al. 2016). Locust bean gum, vegetable gum and arabic gum also act as brilliant fat replacers in bakery items, frozen products, toppings, dressings and spreads.

Pectin

Pectin is a natural polymer found in the primary walls of non-woody plant cells which are widely used in the food business as hydrocolloids (Endress and Christensen 2009). Nowadays, pectin is generally obtained from apple or citrus peel and is used in food items like cakes, cookies, dressings, spreads and frostings, soups and sauces. Pectins used for fat replacement have a degree of esterification (DE), i.e., the percentage of galacturonic acid units that are methyl esterified. According to DE, a variety of fat-replacement pectins are available in the market (Table 1) like low methoxy (LM) or high methoxy (HM) pectins. According to DE, commercial LM-pectins range between 20–40% and 55–75% for HM-pectins (Omayma and Youssef 2007). It contains small particles that resemble fat globules and provides the mouthfeel and sensation as that of fat. Its conventional uses as a gelling agent, thickening agent, and stabilizer are being supplemented by its rising use as a fat replacer and health-promoting functional ingredient in the food industry (Zhang 2018).

Table 1.

Common fat replacers available in the market

Fat replacer	Type of fat replacer	Commercial name	Company	References
Cellulose	Carbohydrate based	Solka-Floc	International Fiber Corporation	Morse (1982)
Maltodextrin	Carbohydrate based	Paselli SA2	Avebe	Bamford and Kelly (1992)
Microparticulated protein	Protein based	Simplesse	Nutra Sweet	Anthony et al. (1992)
Modified whey protein	Protein based	Dairy Lo	Ault Foods	Pordy (1992)
Sucrose Polyester	Lipid based	Olestra	Proctor & Gamble	Larry et al. (1999)
Salatrim	Lipid based	Benefat	Danisco	Robert et al. (1994)
Caprenin	Lipid based	Caprenin	Proctor & Gamble	Costello et al. (2010)
Oatrim	Carbohydrate based	Beta-Trim	Quaker Oats Company	Dendooven Van et al. (2011)
Oatrim	Carbohydrate based	Beta-Trim	Quaker Oats Company	Dendooven Van et al. (2011)

Cellulose

Cellulose is mainly considered a dietary fiber and is a multifunctional ingredient that is used to improve sensory properties. (Sandrou and Arvannitoyanis 2000). It tends to form a gel when comes in contact with water and has generally been used as a food stabilizer due to its properties like glossy appearance as that of fats, mouth-feel and no contribution to calories, which makes it an excellent fat replacer. Powdered cellulose, commercially known as 'Solka-Floc,' is a non-digestible and insoluble fiber available on the market and is majorly used in bakery and fried items because of its tendency to absorb less fat as it binds with water preferentially. As a result, less fat is absorbed by food while frying (Solanke et al. 2016).

Maltodextrin

Maltodextrins are α-D-glucans with a low degree of polymerization that are produced by partial hydrolysis of starch by enzymes or acids (Peng and Yao 2017). It has a high water-holding capacity and creates a thermos-reversible gel with water, giving it a mouthfeel similar to that of fats. Some commercial maltodextrin-based fat replacers (approved by USDA) include Paselli SA2 from potato starch, Maltrin M040 from cornstarch and Oatrim from oat starch, which is a combination of oat β-glucan and oat maltodextrins (Chen et al. 2020). In research conducted by Puligundla et al. (2015), native or cross-linked starch was used as a fat substitute in mayonnaise which contains up to 50% fat reduced-fat. It was found that the mayonnaise with cross-linked starch produced greater sensory quality than the full-fat control.

Oatrim

Oatrim is a USDA approved fat replacer derived from a combination of oat β-glucan and oat maltodextrins. It is a white powder made up of soluble glucan and amylodextrins which is concentrated, refined, water-soluble, and practically tasteless. It offers health benefits like protection against coronary heart diseases and cholesterol-lowering effects on the body (Chen et al. 2020). When mixed with water, it creates a fat-like gel that delivers 1 Cal/g, compared to 9 cal/g for fat (Wekwete and Navder 2008). It is heat-stable and has been used to successfully substitute fat in baked goods and chocolates (Sandrou and Arvantoyannis 2000).

Protein based fat replacers

Most protein-based replacers are made of microparticulated protein, such as Simplesse, which is used in ice cream, milk protein and whey protein concentrate (Solanke et al. 2016). As the name suggests microparticulation creates very small particles which provide a creamy mouthfeel to the final product (having reduced fat content). Owing to the fact that the structure of protein-based fat replacers can be altered on the application of heat treatment, these are not suitable for baking and frying. They tend to get gelled up and lose their creaminess due to heat therefore, these replacers can be employed in manufacturing cold bakery products like butter, cheese, dairy products, ice cream, mayonnaise, salad dressings and sour cream (Yashini et al. 2021).

Microparticulated protein

Microparticulated protein (MPP) is derived from milk protein or egg white protein and have been marketed since long by the name Simplesse and trailblazer. The particular shape, size and concentration of MPP is what provides it with fat like creaminess and richness (Ipsen 2017). MPP fat replacers provide 1.33 cal/g, as compared with the 9 cal/g of regular fats. One gram of Simplesse when used in ice cream can replace three grams of fat. It is not suitable for frying at high temperature, but it can be employed in a wide range of heat-sensitive applications, including ultra-high temperature processing canning and pasteurization (Omayma and Youssef 2007).

Modified whey protein

Modified whey proteins (MWP), alone or in combination with other carbohydrate-based ingredients, gives food a creamy texture (Kusio et al. 2020). It replaces fat by four calories per gram and is potentially used in frozen dairy products such as ice-cream, cheese and yogurt (Yashini et al. 2021). Low protein components like dry whey (sweet or acid) and decreased lactose whey are commonly used for bulking, sweetening, and maillard browning while high protein part like whey concentrate and isolates is utilized for its functional, nutritional and textural properties (Banes et al. 2014). MWP is marketed as Dairy-lo and is desirable due to its ability to prevent shrinkage and iciness in frozen food products. Whey and MWP also enhance solubility, oil binding ability, surface hydrophobicity and foam stability and also helps in mimicking the creaminess of fats (Sun et al. 2015).

Casein

Casein is found in milk as big spherical micelles which form nano particles and provide the majority of the physical sensation in the mouth. Casein has a good thermal stability of up to 140 °C and is extensively used as a fat substitute in dairy products such as cheese, spreads, dips, and yogurts (Yashini et al. 2021). Its emulsification properties improve fat and water binding, as well as textural and sensory aspects of food products. The rheological and sensory properties of fat- reduced vanilla ice cream containing milk protein concentrate were observed by Mostafavi et al. (2017) and they concluded that sensory properties like firmness, smoothness, melting rate, coldness, mouth coating and overall acceptance and further viscosity was similar to that of full-fat ice cream.

Soy protein isolate

Soybean contains about 40% protein including glycinin, a major protein found in soybeans, is known for its ability to form a gel and emulsify. Proteins have a balanced amino acid composition and can decrease cholesterol thereby preventing cardiovascular illnesses, in addition to providing functional characteristics. Glycinin can be separated from soy protein by pH shift method and cryoprecipitate technique (Chin et al. 2000). Soy protein isolate (SPI) is made from a defatted soy flour slurry whose pH is adjusted to solubilize the protein using ultrafiltration (Edwards 2019). It is then dried and used in products such as meat, dairy, bakery, and candy. The various soy-based fat replacers available in the market are Supro, ProPlus, and Supro Plus (Solanke et al. 2016).

LITA

LITA® is a zein protein-based water-dispersible microparticulated fat replacer and has a low calorific value of 4 cal/g and replacing fat with a zein-based fat replacer could help consumers consume fewer calories (Gu et al. 2016). Microparticulation of zein protein is achieved by solubilizing the protein in organic solvents and then introducing the solution into an aqueous solution, resulting in protein precipitation in the form of microparticles suspension (Cheftel and Dumay 1993). This leads to the formation of protein microparticles that are heat stable and water- insoluble. LITA® microparticles have a homogeneous spherical shape with particle sizes ranging from 0.1 to 8 μm, a smooth surface, and are tightly packed with proteins (Yashini et al. 2021).

Fat/lipid-based fat replacer

Fat-based fat substitutes have chemical structures that are similar to triacylglycerol but have lower or no calorie content or triacylglycerol with specific configurations to reduce overall caloric content (Omayma and Youssef 2007). They can be used to replace fat on a gram-for-gram basis. The most well-known fat substitutes, Olestra and Salatrim, are made through a chemical reaction between sugars and fatty acids or by modifying triglycerides (Sandrou and Arvanitoyannis 2000).

Olestra

Olestra is chemically derived as sucrose polyester and is made of a mixture of hexa, hepta and octaesters of sucrose with 6–8 long-chain fatty acids extracted from edible fats and oils using the process of chemical transesterification. This famous fat substitute developed by Proctor and Gamble is a non-digestible fat replacer and replicates fat in terms of organoleptic and thermal properties. Olestra is not hydrolyzed by stomach or pancreatic enzymes due to its large size and non-polar fatty acid content which prohibits its hydrolysis by the digestive lipases (Ognean et al. 2006). The USFDA has approved the use of olestra as a replacement for fats and oils in savory snacks like potato chips, crackers and cheese puffs (Oreopoulou 2006). Although olestra is non-toxic, genotoxic and carcinogenic still can cause problems such as increased bowel movement, stomach ache, vomiting, and reduction of vitamins A and E levels in the body (Elangkovan and Ganapathy 2020).

Salatrim

The name “Salatrim” stands for short and long-chain acid triglyceride molecules (Sandrou and Arvanitoyannis 2000). It is the generic name for a family of structured triglycerides that comprises a mixture containing at least one short chain fatty acid (primarily C2:0, C3:0, or C4:0) and at least one long-chain fatty acid (predominantly C18:0, stearic acid) randomly attached to the glycerol backbone (Ognean et al. 2006). Owing to the presence of varying proportion of short and long chain fatty acid salatrim possess a wide range of functional and physical qualities, such as melting points, hardness, and appearance. Unlike olestra, salatrim cannot be used for frying as it can only be used in cold conditions and at a pH of 3–7.5 (Omayma and Youssef 2007). It provides only 5 cal/g and its calorie reduction is based on two principles viz short-chain fatty acids (e.g., butyric) give fewer calories per unit of weight than longer-chain fatty acids and stearic acid (Salatrim's major long-chain fatty acid) is only partially absorbed by the body (Solanke et al. 2016).

Caprenin

Caprenin (caprocaprylobehenic triacylglyceride) is manufactured from glycerol by esterification with caprylic (C8:0), capric (C10:0), and behenic (C22:0) fatty acids (Costin 1999). Caprenin supplies just 5 cal/g as behenic acid is only partially absorbed and capric and caprylic acids are more easily digested than other long-chain fatty acids (Ognean et al. 2006). Since it has properties similar to those of cocoa butter, it is used as its substitute in candy bars as well as confectionery coatings for nuts and cookies (Singh et al. 2020). It can also be used at a temperature of up to 132 °C which is particularly well suited for confectionery items. Caprenin in conjunction with polydextrose was temporarily commercially available in low-calorie and low-fat chocolate bars (Sandrou and Arvanitoyannis 2000).

Emulsifiers

Emulsifiers work as fat extenders by making a small amount of fat appear larger due to their fat-sparing action. Although they contain similar calories as fats less amount is required to produce fat-like properties. They are commercially available under the names Dur-Lo®, EC^T-25 and provide both hydrophilic and lipophilic properties which allows them to maintain the interface between fat and water droplets using hydrogen bonding (Kothalawala et al. 2018). As emulsifiers are restricted in their use, their role as fat replacers is limited when combined with other components. They can be used to reduce fat content in items including yellow-fat spreads, biscuits, cakes, baking emulsions, ice cream, and salad dressings by up to 30%. They also impart flavor and provide lubrication and stabilization to the cake frostings, baked goods, spreads and frozen desserts (Oreopoulou 2006).

Application of fat replacers in various food products

Fat replacers are widely used for the development of bakery products, dairy, confectionery, spreads etc. due to their properties viz thickening agents, stabilizers, emulsifiers and other functional properties. A brief overview of some fat replacers and their application in various food products is presented in Fig. 1 and Table 2.

Fig. 1.

Types and applications of a few fat replacers

Table 2.

Application and functions of different fat replacers

Fat replacer	Source	Energy density	Function and uses	References
Salatrim	Acyl triglyceride molecule	5 cal g−1	Aids in jncreasing overrun and improving mouthfeel of dairy products	Ognean et al. (2006), Jadhav and Annapure (2021)
			Helps in carrying flavour and extending shelf life of bakery products
			Used in cheese, sauces, dairy and bakery products
Caprenin	Caprocaprylobehenic triglyceride molecule	5 cal g−1	Provide cocoa butter like properties and act as an emulsifier	Ognean et al. (2006), Zam (2020)
			Used in candy, confectionery, nut and cookie coatings
Olestra	Sucrose polyester	Non calorific	Imparts texture and crispiness to savory snacks	Elangkovan and Ganapathy (2020)
			Used in potato chips and other salty snacks
Simplesse	Whey protein or egg white protein	4 cal g−1	Provides creaminess in ice cream and also act as an emulsifier in cheese, sauces and other dairy products	Yashini et al. (2021)
			Used in cheese, yoghurt, mayonnaise and ice creams
Trailblazer	White egg protein, serum protein mixed with xanthan gum	4 cal g−1	Helps in forming a homogeneous mixture and also act as a stabilizer thus aids in retaining structure of baked products	Goswami et al. (2019)
			Used in dairy, soup, sauces and baked foods
Casein	In milk as big micelles with a spherical form	3 cal g−1	Improves water and fat binding, viscosity and mouthfeel of food products	Yashini et al. (2021)
			Used in cheese, spreads, dips, yoghurt and ice cream
Carageenan	Sulphated polysaccharides extracted from red seaweed	Non calorific	Imparts texture and fat like mouthfeel to food products	Solanke et al. (2016)
			Used in desserts, chocolate, ice cream and yoghurt
Pectin	Citrus peel	Non calorific	Act as a gelling and thickening agent and imparts stability to mixtures	Colla et al. (2018), Picot-Allain et al. (2020)
			Used in jam, jellies, marmalades, frostings
Gums (Guar, locust bean, xanthan)	Galactomannan, seeds of the tree Ceratonia silique, Xantomonas Campestris	Non calorific	Aids in retaining moisture and keeping baked goods moist	Peng and Yao (2017)
			Used in baked food products

Bakery products

In preparation of bakery products such as bread, biscuits, pastries, cakes, and others require the use of different types of various types of bakery fats, which are broadly classified as shortening and butter. These fats add lubrication, aeration, and softness to the finished product (Oreopoulou 2006). In cakes, fat can contribute to increased leavening, tenderness and a finer crumb through a combined effect of trapping air cells during the creaming process (Colla et al. 2018). Various fat mimetics like wax-based oil gels, polymer gels prepared through indirect methods, and structured emulsions have been explored for their potential to act as a replacement for bakery fat. On comparing the dough properties (such as density, microstructure, and rheology) and finished product characteristics (texture, stability, and sensorial aspects), it has usually been found that although the rheology of intermediate products prepared using fat mimetics is less developed, the properties of baked products were found to be comparable to the products prepared with bakery fats (Curti et al. 2018). In a study performed by Lee (2018), it was observed that up to 50% of shortening could be replaced with fat mimetics in muffins without negatively affecting the final qualities of baked products, even though the viscoelasticity of the batter was reduced. In another study conducted by Colla et al. (2018), Oatrim acted as a good fat replacer in biscuits and was able to keep most sensory attributes of a typical biscuit even at 100% fat replacer, although a decrease in brittleness and hardness was observed (Wekwete and Navder 2008).

Dairy products

A wide variety of dairy products are consumed on a regular basis which include butter, yogurt, and cheese. From a colloid science point of view, these products could be broadly classified as structured emulsions (butter and butter spreads) and coagulated gels (various cheese types). These products vary in microstructure greatly, however, all of these contain milk fat in dispersed or bulk form (Patel et al. 2020). The underlying colloidal network of crystalline particles is provided by the high melting fraction of milk fat, which regulates the macrostructure and organoleptic qualities of dairy products such as creaminess, smoothness, spreadability, and voluminousness. The impact of various quantities of inulin as a fat replacer on ice cream quality was explored by Tiwari et al. (2015). The experimental ice creams contained inulin as a fat substitute at 2, 4, and 6% and were compared to a control with 10% milk fat. Their chemical composition, overrun, water activity, viscosity, melting rate and hardness were determined and the ice cream samples' sensory qualities were assessed during storage. The overall acceptance of ice creams prepared with 2 and 4% substitution was comparable to that of the control.

Chocolate and confectionery products

Chocolate contains up to 20% saturated fats on average which stimulates the need of the consumer for healthier formulations. One major factor affecting the quality of chocolate and confectionery products is the stability of oil, migration, and leaks during storage. Because solid fat works as an oil binder, fat mimetics must be carefully designed to prevent jeopardizing product stability (Patel et al. 2020). The complete replacement of oil binders is also studied in chocolate spread and peanut butter in which structuring agents (shellac wax and hydrophilic cellulose derivatives) were employed successfully to duplicate the oil binding functionality in peanut butter and chocolate paste in two separate tests. Chocolate spread was made with shellac oleogel in 1:1 ratio in which shellac wax functioned as an oil binder and the samples did not show any oil separation even after four weeks of storage (Patel et al. 2014).

Spreads and margarine products

Table spreads and margarine are emulsified products with varying fat levels. For instance, low-fat (35–42% wt.) and very low-fat (< 30% wt.) spreads are used for spreading on bread while high-fat (70–82% wt.) spreads are mostly used in cooking/frying applications (Patel et al. 2020). Solid fat has three important functions in these products firstly it tends to form a crystalline fat network in the continuous oil phase, which influences structure properties like texture, firmness, and spreadability (Pușcaș 2020). Secondly, it forms fine fat crystals at water–oil interfaces, which stabilize dispersed water droplets; and at last, it contributes to sensorial properties like mouthfeel and flavor release. Wax-based oil gels have been found to mimic all or most of these functions due to which they are the most commonly studied fat mimics in emulsified goods like spreads and margarine (Hwang et al. 2013).

Health implications of fat replacers

Concerns about the safety of compounds added to compensate for fat removal highlight the significance of educating the general public about fat substitutes and how to use them effectively (Archer et al. 2004). Various health implications of fat replacers both beneficial and adverse are given in Fig. 2. Oatrim, a carbohydrate-based fat replacer approved by the FDA, has been scientifically evaluated and demonstrated to decrease the level of cholesterol and the risk of coronary heart diseases in humans (Tosh and Bordenave 2020). Xanthan gum when consumed in doses ranging from 10.4 to 12.9 g per day acts as a bulk laxative with no adverse nutritional or physiological consequences and a 10% drop in cholesterol can be seen (EFSA Panel 2017). It also aids in weight loss and obesity prevention by the means of greater satiety and delayed stomach emptying. Guar gum can only be utilized at a low concentration of 0.5–1.0 percent for its positive benefits at a concentration higher than this it not only interferes with nutritional and sensory properties of the food which decreases consumer acceptance but also leads to decreased protein efficacy and lipid utilization (Mudgil et al. 2014). Several studies about pectin have also found that just like guar gum it also aids in weight loss. It also possesses antiviral activity and lowers total cholesterol, blood glucose as well as insulin levels in individuals (Endress and Christensen 2009). Maltodextrins have several applications in functional foods and beverages like providing energy and encapsulating vitamins and helping in lowering the risk of gastrointestinal distress when compared to the usage of glucose or sucrose, which create a high gastro-intestinal osmolality causing gastrointestinal irritation during endurance sports. However, because glucose from digested maltodextrins is quickly absorbed in the small intestine it may result in a higher glycemic load and, as a result, higher post-meal glycemia, both of which are considered unhealthy (Hofman et al. 2016). Fat replacers based on β-glucan have been shown to demonstrate a reduction in heart diseases of consumers when 0.75 g of β-glucan/serving is incorporated into food (Lim et al. 2010). Some fat-based fat replacers like polydextrose and olestra can also contribute to negative health consequences. It has been reported that individuals who consume high amounts of polydextrose may develop a laxative effect. Because olestra is lipid soluble, non-absorbable and non-digestible, it has the potential to obstruct the absorption of other foods, particularly lipid soluble foods if consumed at the same time. It also interferes with the absorption of fat-soluble vitamins A, D, E, and K, as a portion of those components may get mixed with olestra in the gastrointestinal system and be expelled with it (Ognean et al. 2006). When ingested in high numbers, olestra can also induce stomach cramps and stool softening or loosening (Elangkovan and Ganapathy 2020). The various benefits, as well as adverse effects of different fat replacers, is presented in Fig. 2.

Fig. 2.

Beneficial and adverse effects of different fat replacers

Regulations for fat replacers

Fat replacers are regulated by FDA and are categorized as food additives or generally recognized as safe (GRAS) ingredients (Vaclavik and Christian 2008). No special authorization is required for fat substitutes produced from a combination of commonly used substances such as starches, gums, fibers, or proteins and they come under the category of GRAS. According to the FDA, xanthan gum can be safely added to food items under the parameters outlined in CFR Title 21 Volume 3 Part 172. Pectin and maltodextrin have also been given a GRAS status and they can be used in food directly in accordance with Good Manufacturing Practices (GMP). Maltodextrin should be derived from corn starch or any other starch resembling the chemical structure of maltodextrin derived from rice, maize, or potato. Microparticulated protein-based fat mimetics are also considered GRAS substances (Oreopoulou 2006). Whey protein concentrate (WPC) used should be derived from pasteurized milk or WPC itself should be pasteurized before using it. The protein content of WPC should be minimum of 25% and the acidity of WPC should be adjusted by adding pH-adjusting substances that are both safe and effective. WPC must be listed on the label of the finished product as "whey protein concentrate" if it is present in it. Some federal regulations may also limit the use of fat replacers in certain foods for example, olestra is only approved for addition in savory snacks (Ognean et al. 2006). To compensate for any hindrance in fat absorption caused by olestra 1.9 mg alpha-tocopherol equivalents per gram of olestra; 51 retinol equivalents per gram of olestra (as retinyl acetate or retinyl palmitate); and 12 IU vitamin D per gram of olestra should be added. This addition of vitamins should also be mentioned on the label with a declaration “Dietarily Insignificant”. The Nutrition Labeling and Education Act of 1994 governs the labeling of foods containing fat substitutes. The fat replacer's common and usual name must be included on the ingredient statement along with its caloric and the nutritional impact on the Nutrition Facts panel. Any claims showing a reduction in fat, calories, or both must adhere to the FDA's fat- and calorie-reduced claims guidelines (Oreopoulou 2006).

Conclusion

Fats play a very significant function in food matrices and impart physical and sensory properties to the food products. Fat replacers have facilitated the emergence of low-fat and fat-free foods that mimic the flavor and texture of high-fat foods. Although using fat-modified foods can help to avoid weight gain and related chronic diseases but they still don’t replace the need for practicing good nutritional habits. The fat replacers currently available in the market do not contribute to all the sensory and functional properties of conventional fats. An ideal fat replacer must be safe for consumption, cost-effective, low-caloric, suitable for cooking, contribute to sensory properties and at the same time play functional role in the food products. Nonetheless, it can be claimed that fat replacers may help in meeting the required aims of current dietary recommendations as long as they are coupled with physical activity and mindful eating. Further research is needed in order to explore other potential sources of fat-replacers which can be successfully utilized for the development of new and healthy products in food industries as an effective alternative of fats.

Abbreviations

USDA

United States Department of Agriculture

FSSAI

Food Safety and Standards Authority of India

TFA

Trans-fatty acids

GI

Gastrointestinal

DE

Degree of esterification

LM

Low methoxy

HM

High methoxy

MPP

Microparticulated protein

MWP

Modified whey proteins

SPI

Soy protein isolate

USFDA

United States food and drug administration

GRAS

Generally recognized as safe

GMP

Good manufacturing practices

WPC

Whey protein concentrate

IU

International unit

Author contributions

VS and JK are the sole authors of the review article. JK supervised the work and edited the manuscript. KS, MP, PR, JS and VB have contributed equally for the literature collection, manuscript documentation and its revision.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declarations

Conflict of interest

There are no conflicts of interests to declare.

Consent to participate

All the authors have read and approved the manuscript and all are aware of its submission to the journal.