Fats have a multifaceted functionality affecting nutrition, flavor and palatability, texture, shelf-life extension, lubrication, volume/bulk, satiety, and heat transfer. To date, there still is no single “silver bullet” replacement for fat in any food application. Instead, there are customized replacers. And in many formulations, these replacers perform “double-duty” as emulsifiers.
Fat-replacement requires a systems approach wherein several ingredients (and conditions) work compatibly to replicate the various functionalities of fat unique to that food application. Depending on the system used, the resulting lower- or alternate-fat product can reap the added benefits of increase in fiber or protein for consumers.
In high-moisture liquid or semisolid foods, fat is an integral part of the artificially created or naturally occurring emulsion. Because fat is inherently immiscible with the aqueous phase, emulsifiers are required to stabilize the oil-water interfaces. In salad dressings and mayonnaise—both artificially created emulsions—emulsifiers envelope the globular fat droplets to stabilize them.
In naturally occurring emulsions, such as milk, cream, soymilk, and yogurt, the fat is part of oil-bodies. These are the well-defined structures in which the lipid droplets form the core, and are bounded by specific membrane proteins and polar lipids. When replacing fat, the equation shifts and emulsifiers must follow suit.
Oral processing activates sensory perception which, in turn, influences consumer perception of quality and preference. The sensory perception of fats in the mouth is a complex process involving the time-dependent deformation, structural breakdown, and flow of foods during mastication, all of which affect fat-related sensory qualities such as creaminess, smoothness, thickness, oiliness, and slipperiness.
Research into the physiology of fat perception has identified specific fatty acid receptors in the tongue, as well as recognition that fat metabolism begins within five seconds at the onset of ingestion. This makes it particularly important for product developers to understand that the human brain is not easily fooled by mere taste and texture modification alone.
So...how to lower fat yet get working emulsions in favorite foods? The list of processors and ingredient technologists working on the challenge is about as long as the list of those coming up with unique solutions.
One easy method is simply using mechanical means to purée and blend product to a finely particularized suspension. This works particularly well in certain vegetable-based products such as soups.
For example, Skinny Souping LLC created its line of creamless “creamy” soups by carefully selecting vegetable purées purées for taste and texture, and eliminating the need for cream and starches for bulk and texture.
Other new entrants into the soup sector include Tio Foods LLC.’s line of bottled soups, and Sonoma Brands Inc.’s Züpa Noma line. All these entries replicate creamy emulsions without fat or cream through blending or other mechanical applications.
Another approach to emulsification in the presence of fat replacement is to use starches or proteins that can mimic the organoleptic characteristics of fat. Modified food starch and wheat flour, for example, help reduce the fat and caloric content in formulations such as soups, sauces, and dressings by binding with the liquid component. For example, these are the first ingredients on Campbell Co.’s Healthy Request cheddar cheese soup.
The call for fat reduction continues, even while the message gets more complicated from the nutrition and health standpoint. Simply put, most of what was promoted in the way of dietary fat’s impact on health has been largely overblown and miscommunicated.
Fat is vital to biological function, not only as a concentrated source of energy and storage form for same, but as a carrier of various vitamins and nutrients. Fat is an integral part of every cell in the body.
However, another reality is that, as a concentrated source of caloric energy, lowering the fat in a formulation allows for a reduction of calories that has far less impact on serving size. To achieve a 25% calorie reduction in a 30g/100-calorie product by eliminating carbohydrates or protein would reduce the size of the item by about a fifth. Take out the fat needed to get there, and the product shrinks by only less than half that amount.
But fat reduction also typically deteriorates quality. When the relative volume of fat decreases so, too, do interactions between fat and fat, fat and protein, and fat and polysaccharides—all of which change the rheology of the product. In dairy formulation, this becomes especially challenging.
Decreasing fat in hot chocolate or ice cream lowers their apparent viscosity and they tend to taste watery. Lowering fat in chocolate, sausage, and cheese, increases their elasticity and brittleness and produce hard and springy foods with poor meltability, which in turn affects their taste and aroma.
Fat replacement requires tending to all aspects concurrently and to the changes with change in processing/storage/eating conditions.
First Line Starches
Fat replacers developed to date generally are either carbohydrate- or protein-based, with most of the low-fat products introduced in recent years containing carbohydrate-based fat replacers. These include starches, maltodextrins, polydextrose, gums, and fibers.
Carbohydrate-based fat replacers are projected to grow at an estimated CAGR of 6.2% by 2025, according to Packaged Facts. Carbohydrate fat replacers usually have low calorie density, and effectively provide gelling, thickening, stabilizing, and other texture-modifying properties in many food applications. They are not, however, suitable for fried foods.
When replacing fat in food products such as cheese, sausage, yogurt, mayonnaise, and frozen dessert, starches replace different forms of fats in the different products: fat globules in dairy products, oil emulsions in salad dressings, and intermuscular fats in meat products.
The results include increased product yield, water-holding capacity, and gel firmness; changed viscosity and sensory qualities such as creaminess and tenderness.
Starches are derived as granules from roots, stems, leaves, tubers, and seeds and are largely made up of amylose and amylopectin. Their properties and functionality as fat replacers are affected by granule shape, particle size, and amylose:amylopectin ratios.
Starches with granular sizes similar to those of fat emulsions are potentially good fat replacers by virtue of their dispersion in a form similar to that of emulsion droplets.
Cross-linked starches function like native starches in fat replacement applications but with the added benefit of greater emulsifying power, lower digestibility and fewer calories. When it comes to formulations for health, they also typically have a lower glycemic response.
In dilute liquids like milk, granular carbohydrate fat replacers (GCFRs) are shaped and sized like colloidal fat in milk and disperse individually to replicate their qualities.
In contrast, nongranular carbohydrate fat replacers (NGCFRs) do not mimic the shape and size of fat particles but instead interact with the colloidal proteins to replicate the thickening mouthfeel associated with creamy full-fat milks.
In chocolate milk, carrageenan works well to suspend cocoa particles, preventing separation and provide a creamy mouthfeel.
In concentrated liquids like salad dressings, where fats exist either as individual particles or coagulate units, GCFRs and NGCFRs gel or aggregate to produce microstructured particles that act like the original fats. It works particularly well to select GCFRs with sizes comparable to microstructured fat particles.
In semisolids like yogurt, fat interferes with protein-protein interactions and produces a smooth creamy product that melts in the mouth. In fat-free yogurts, the absence of fat increases the density of protein cross-links which makes the yogurt more chewy than creamy.
Adding GCFRs and NGCFRs disrupts the cross-links of protein matrix to make it softer and more tender, while contributing to a thicker and creamier mouthfeel during mastication and swallowing.
In dry solids like pastry crust, cookies, and shortbread, fats act as plasticizers to separate the layers and create the desired tender friability and crunchiness and a certain smoothness when the fats melt in the mouth during eating.
Carbohydrate fat replacers can help disrupt the formation of solid networks to form layers, but because they do not melt when warmed, they cannot replicate the creaminess of these products during eating.
Maltodextrins, products of partial hydrolysis of starch by enzymes or acids, are a-D-glucans and have a low degree of polymerization (DP). Maltodextrins are labeled with dextrose equivalent (DE) values and lower the DE value, lower the average DP.
Maltodextrins with low DE (DE value of 2–4) have a high tendency to gel, which is suitable for texture modification and, in particular, thickening applications. Better fat-replacing results are obtained when low-DE maltodextrins are processed to form microgels before incorporation into the product.
Source also matters. In edible fat blends, replacing hydrogenated vegetable oil with maltodextrin microgels made with waxy corn starch effectively replaces more fats and stabilizes the system with higher viscosity and tensile elasticity than maltodextrin from potato starch.
In contrast, in some baked products maltodextrins from potato starch offer advantages over other sources. Potato starch’s unique plastic, spreadable, and shortening-like texture, coupled with its lower tendency to retrograde (or harden and make the product stale), gives it the advantage in more solid formulations.
Polydextrose does not occur in nature but is formed by cross-linking glucose and sorbitol randomly. While it is commonly used as a bulking agent to replace sugar, it also can replace 1-30% of fats without adversely affecting the texture of foods such as layer cakes; caramel and other soft candies; and frozen desserts. The average DP of polydextrose is lower than that of most carbohydrate polymers, such as those in native starches, gum, and fiber. Polydextrose is resistant to human digestive enzymes and has low energy density (∼1 kcal/g). It provides high satiety and good prebiotic properties as well.
Gums and Fibers
Gums and fibers are polysaccharides isolated from plants and bacteria. They have a range of molecular structures, glycosidic bonds, and physical properties that help them act as thickeners, emulsifying agents, and textural enhancers. Guar gum, locust bean gum, xanthan, carrageenan, alginate, and pectin, are the major gums for fat replacement. Also common in formulations are the fibers cellulose, cereal brans, inulin, and β-glucan. Gums and fibers are indigestible (0 kcal/g) and also provide prebiotic effects.
Gums and fibers do not, however, structurally resemble fats. They are usually formulated with other fat replacers because they form entanglements and cross-links with other food components such as proteins, starches, and emulsion droplets through hydrogen bonds and hydrophobic or electrostatic interactions to provide the characteristic texture and mouthfeel of fats.
In low-fat mayonnaise, mixtures of guar gum and xanthan gum or citrus fiber simulate the function of oil emulsions. In low-fat ice cream, guar gum and basil seed gum provide better creaminess than guar gum alone.
In baked goods and frosting, where the first step is creaming, gums and fibers help form fat-like microparticulates with starches, proteins, gums, and fibers.
Xanthan gum and whey protein isolate are good substitutes for shortenings and vegetable oils in cake frosting and filling products. Other formulations for constructing similar microparticulates include: protein, starch, fiber, and beta-glucan; cellulose and hydrocolloids such as alginate and xanthan gum; or starch and carrageenan and locust bean gum.
The trend toward cleaner labels and increased sustainability sometimes limits the choice of hydrocolloids or modified starches and paves the way for citrus fiber derived from orange pulp.
Composed of insoluble and soluble fibers, citrus fiber has a unique molecular structure; some protein enables citrus fiber to function like traditional hydrocolloids and aid in fat reduction through thickening, emulsifying stabilization, and reduced syneresis.
The surface area of citrus fiber expands for enhanced water-holding capacity and emulsification properties. Pectin-containing citrus fibers can be activated to produce gelling properties in high-sugar/low-pH food processing conditions.
Artisanal bakers are experimenting with vegetable purées to substitute as much as 50% of the fat in cakes and other bakery items. Squash and cantaloupe purée produce cakes with high volume, greater moisture and minerals, yet fewer calories than the original.
These require balancing with emulsifiers to prevent staling and firming/hardening during storage. This is not too great a challenge for artisanal bakeries that do not have the long shelflife demands of their retail and other foodservice counterparts.
Starting by first creaming fat with naturally occurring materials such as okra gum, apple sauce, pawpaw paste, prune paste, fig paste, or avocado purée can help replicate the taste and texture of full-fat bakery items.
Cooked ground bean products have been shown to work as a substitute for 10-25% of added fat in baked foods and grain-based food applications such as tortillas, brownies, cookies, snacks, cereal, pizza, pasta, crackers, and chips.
Protein-based fat replacers have tremendous potential for use in a variety of products, especially frozen and refrigerated products.
Although protein-based fat replacers are not suitable for fried foods, they can be used in many heated applications, such as creamy soups, pasteurized products, and baked goods.
Gelatin is a highly purified protein and can serve as an effective fat-replacer, depending on the food application. Hydrated gelatin contributes lubricity and lends melt-in-the-mouth creaminess to yogurt and frozen desserts. Gelatin has a high water binding capacity that allows it to replace a large percentage of the fat content of yogurts and frozen desserts and helps create a fat-like creaminess in emulsions.
In foamed dairy-based desserts, such as mousse, gelatin decreases the surface tension of the water, enabling a foam to be generated by mechanical whipping or gas injection, and then stabilizes the foam by gelling.
Gelatin helps minimize the absence of fat without sacrificing taste or texture in reduced-fat butter and cheese. Gelatin also works synergistically when combined with some hydrocolloids.
There are number of microparticulated, reduced-calorie (1-2 kcals/g) fat replacer ingredients made from whey protein or milk and egg protein for a number of applications including: dairy products (e.g., ice cream, butter, sour cream, cheese, yogurt), salad dressing, margarine- and mayonnaise-type products, as well as baked goods, coffee creamers, soups, and sauces.
Modified whey protein concentrate with controlled thermal denaturation offers a functional protein with fat-like properties for applications in milk and other dairy products, including cheese, yogurt, sour cream, and ice cream. It also works well in that capacity in baked goods, frostings, salad dressings and mayonnaise-like items.
Ripple Foods Inc. utilizes novel technology to produce neutral-tasting pea protein isolates to produce an allergen-friendly milk-like product with 8g of protein per 8oz serving, and 20% fewer calories than 2% dairy milk. It also has only a sixth of the saturated fat and half the sugar.
Whole algae flour, which is not a protein isolate or concentrate, is about 65% protein. Derived from non-bioengineered/non-GMO and gluten-free algae, it may be used to replace fat and augment dietary fiber, beneficial lipids, and all the essential amino acids in baked foods, snacks, beverages and bars. An added benefit: Microalgae has 32mg/g of the DHA form of healthful omega-3 fatty acids.
Fat for Fat
While using fat to replace fat might seem like a fool’s exercise, these systems rely on significantly enhanced functionality and therefore reduction in total calories and fats even with the same amount of calories as fat (9 kcal/g).
Food technology has advanced a number of fat-based alternatives for fat reduction in cake mixes, cookies, icings, and numerous vegetable dairy products.
These fat-derived replacers for whole fats and oils are made mixtures of vegetable oil mono- and diglyceride emulsifiers with water to replace all or part of the shortening in baked goods. Such emulsifiers are playing an increasing role in product quality since the ban of partially hydrogenated oils and fats (PHO) by the FDA.
When replacing a conventional monoglyceride-type emulsifier in baking with the next-generation emulsifier, compare not only the melt point of the product but also the melt properties throughout the entire temperature range of production and storage. Suppliers can provide a Differential Scanning Calorimetric (DSC) profiling for this comparison work.
In the Pipeline
A new emulsifier soon to be on the market includes propylene glycol monoesters (PGME) for primary application in sweet goods, bakery mixes and similar products. The polyglycerol monoesters and mono- and diglycerides. They are derived from non-GMO vegetable oils and are activated via extrusion on to the outer surface of the starch particles so as to exponentially expand the resulting surface area for rapid functionality, fast uptake, and almost instant incorporation of air into a cake batter.
The activated emulsifier both aerates batters to form the cake’s structure and stabilizes water and oil components.
Such emulsifiers also offer labeling benefits: they are clean label as modified food starches. It is important to note that these new emulsifiers are also not “slam-dunk” and rely tremendously on the type of fatty acid in the fats selected.
The fatty acid composition is foundational to the end product and pinpointing the right attributes can help create proprietary blends for tremendous competitive advantage. Additionally, the new emulsifiers enable use of liquid oils, to dramatically reduce saturated fats and also eliminate trans fats and PHOs.
Another emerging emulsifier in the marketplace is esterified propoxylated glycerol as a new solid fat replacement that can lower total calories by up to 45% per serving, and reduce up to 80% of the total fat in a range of foods. Made from naturally occurring vegetable fats, it is deemed GRAS by the FDA for use as a fat replacement.
In today’s food-aware climate, the pressure toward shorter ingredient statements with ingredient names consumers can recognize makes it paramount for product development to understand not just the properties of fat and food systems, but the process and the journey of the ingredients. A scientific understanding of the food system and its physiological effects are crucial to delivering on the taste and health benefits, as well as the clean label demand, that brings consumers to the table.
Kantha Shelke, PhD, is a principal at Corvus Blue LLC, a Chicago-based food science and research firm specializing in industry competitive intelligence, expert witness services, and new product/technology development and commercialization of foods and food ingredients for health and wellness. Contact her at firstname.lastname@example.org.
Eggs—The Great Emulsifier
American Egg Board and Christine Alvarado, PhD
Nature designed multiple functions into the egg, including its ability to emulsify. While most commonly associated with mayonnaise, the emulsifying capacity of whole eggs, egg yolks and even egg whites plays a role in baking and other applications.
Eggs in either fresh liquid, frozen, or spray-dried form have the capacity to emulsify, with no essential difference found between them. The most popular forms however, include liquid, refrigerated whole eggs or frozen yolks. Frozen yolk has 10% added salt or sugar to promote a smooth, creamy, viscous yolk. Egg white emulsifies due to its albumin protein component, while for egg yolk it is its lecithoprotein content.
As an emulsifier, eggs act as a stabilizing agent by reducing surface tension, and reduce the force required to create the droplets that comprise an emulsion. The reduction of surface tension is due to the lecithin or phosphatidylcholine in the yolk. This ampiphilic molecule has two ends, one hydrophobic and one hydrophilic. This reduces oil/water interfacial tension, minimizing the energy required to form an emulsion.
There are multiple factors that can affect an emulsion’s stability such as temperature, mixing speed and time, and other impacts. Two critical aspects are viscosity and the size and uniformity of the droplet.
An emulsion is thicker or more viscous than its separate components. Egg yolks provide a viscous, continuous phase that promotes stability in emulsions by preventing the dispersed oil droplets from moving around and coalescing. Adding egg yolk to whole eggs increases emulsion viscosity, giving it greater stability.
The smaller the droplet and more uniform in size, the better the emulsion and the better the mouthfeel and texture of the finished product. When mixed at the proper speed, adding ingredients in the proper order, formulators can control droplet size and dispersion. For example, oil must be added slowly to water so that the lecithin within the egg yolk can thoroughly coat the small droplets. This coating acts as a barrier to prevent the droplets from joining back together (flocculating) to enhance emulsion stability and improve product appearance and texture.
In ice cream, eggs added during the freezing process help promote a smoother texture and ensure the ice cream does not melt rapidly after serving. Emulsifiers also help improve freeze/thaw stability, an important quality for ice cream and other frozen treats, such as sorbets, milkshakes, mousse, and frozen yogurt.
Within the commercial baking industry, a proper emulsion impacts both product and process. Eggs can help increase product volume and supply a tender crust and crumb. It also helps create a finer and more uniform cell structure, a bright crumb color, and slow the crumb from firming. All increase product shelflife. Emulsification activity also enables proper blending of ingredients and protects doughs during mechanical handling.
With food safety so vitally important, it’s worth noting that all further-processed egg products are pasteurized. This pasteurization does not affect the egg’s emulsifying capacity.