Fats play so many roles in foods that replacing them requires an in-depth understanding of every one of their multiple functions
Replacement of fat in formulations, without sacrificing taste and functionality, is a challenging (but blooming) opportunity for prepared food makers. Although “fear of fat” among consumers has died down considerably as more detailed research and information on fat in the diet continue to come to light, projections by Sloan Trends Inc. indicate fat-free and low-fat item sales will enjoy big growth–as much as 16% in 2016—with a significantly greater proportion of males driving the category than ever before.
Researchers from Yale University and the University of Manitoba, Canada, discovered that culturally held stereotypes about gender (that women eat more healthfully than men and the latter tend to gravitate towards unhealthy foods like fried chicken and potato chips) implicitly influence food preference. Plus, cutting fat from the diet is still perceived as a “quick fix,” since the calories from fat are more than double those of protein and carbohydrates.
Reducing fat is not a simple undertaking, largely because of its multi-functional role. Fat strongly defines the physicochemical characteristics, sensory attributes, nutritional profile, and the physiological response of the food. Fat functionality also is unique to each food type, and changes distinctly with formulation, processing, and how it is consumed.
What further confounds the already difficult task of fat replacement is that consumers will typically—and soundly—reject reduced-fat and no-fat products if it means having to give up flavor. Health and affordability are almost equally as important.
A primary complication in fat replacement, perhaps even greater than texture challenges, is that low-calorie and low-fat foods tend to be not as filling. Where simply removing fat once was a guarantee of acceptance from nutritionists, fat replacement today requires attention to increasing the feelings of satiety and satiation.
Satiety can be thought of as long-term satisfaction from a meal tied to lack of feeling hunger. Satiation is the immediate, post-prandial cessation of hunger, secondary to physical sense of fullness. Both contribute to reduce overall food (and calorie) intake, and a replacement must do just that in order to get a positive nod from public health experts.
The category of oil-in-water (O/W) emulsions, which includes so many beverages, dips, desserts, dressings, sauces, and soups, also happens to be a major source of fat-derived calories for most consumers. These O/W emulsions consist of small fat droplets dispersed within an aqueous medium that can contain a variety of water-soluble or -dispersible ingredients.
Typical examples are salts, sugars, thickening agents, and gelling agents. The type and amount of fat often account for a major part of the overall structure of these food products, their calorie content and also their organoleptic qualities.
The properties of each type and form of fat largely define the taste and other desirable quality attributes of emulsion-based foods. In kefir and other cultured dairy beverages, milk fat contributes to a creamy texture, as well as the muting of acidity from the fermentation. But other aspects of a formulation can be manipulated to make similar contributions. Lifeway Foods Inc. jumped onto the protein train with a new line of protein kefir drinks with reduced-fat and nonfat cultured smoothie beverages with 20g of protein per 8oz serving.
The products appeal not only as post-workout recovery tools, but also to help control snacking and, thus, control hunger and facilitate weight management. The special kefirs use a combination of inulin and pectin to mimic the smooth creaminess of fat, as well as to bulk viscosity and increase satiation.
The addition of vegetables such as beets, cucumber, or tomato purees in its veggie kefir line was done to not only reduce the amount of sugar added, but also to take advantage of the cellular matrices of these vegetables. This contributes a rounded, smooth mouthfeel to the reduced-fat, high-protein beverages.
In cheese, apart from its nutritional significance, fat contributes to its sensory and functional properties, such as melting while cooking and in the mouth. Cheese also is a concentrated source of calories—more than half from fat—but its equally high protein gives it one of the highest satiety factors for a food. Although consumers treasure cheese for these unique characteristics, they also seek cheese with lower calories and lower fat content.
The Big Cheesy
Removing or reducing fat in cheese results in a rubbery texture and a drastic drop in flavor, and adds bitterness and other off-flavors if not done with technical expertise. In formulations, loss of fat in cheese also can lead to clumping and other poor melting characteristics, as well as imparting a dull grey color. These all are serious defects that will certainly discourage consumption.
Reducing fat in cheese is especially difficult, because fat serves as a plasticizer in cheese; it interferes in the protein matrix and keeps it supple. Reducing fat reduces that plasticizing effect and thereby makes the protein matrix more compact. The resulting texture becomes harder and chewier.
To reduce the fat in cheese, the approach differs, depending on the type of cheese and the desired application. In some low-fat cheeses, inulin has proven suitable for replacing fat by stabilizing the structure of the aqueous phase of cheese and contributing to improved creaminess—resulting from its interactions with whey protein and caseinate. High-performance (HP) inulin with long-chain polymerization (average polymer units = 25) within a high range of molecular distribution (from 11-60 polymer units) works particularly well as a fat replacer.
In the absence of residual sugars and smaller chain oligomers, the HP inulin forms inulin microcrystals that, when sheared with water or milk, provide a fat-mimetic property significantly double that of regular inulin and without its tell-tale sweetness. A mixture of carob bean gum and guar gum, plus whey protein concentrate, can replicate the smooth and creamy plasticizing effect of the naturally occurring milkfat of Kraft Foods Inc.’s Philadelphia brand cream cheese in the reduced-fat versions of the product.
Cream cheese made with inulin does not exhibit syneresis because of the excellent water-binding capacity of inulin compared to starches and gums. Franklin Foods Inc. is using inulin to re-invent the cream cheese category toward making it more relevant for today’s consumers with its Greek cream cheese.
The focus on protein is emphasized on the package front of its 8oz bar, with a claim of “four times more protein and less than half the fat of regular cream cheese.”
The reduction in fat in Franklin Foods’ cream cheese is brought about by the direct-set process. It makes the cream cheese through acidification, so it retains the whey, and therefore has more protein; meanwhile, inulin helps interfere with the protein matrix for a creamier but denser mouthfeel.
Fats Out, Carbs In
A recent “Health Focus International Natural Survey” reported cereal starches ranked among the top 10 most recognized and accepted ingredients for American consumers. Thus, the fact that extruded corn flour, labeled as corn starch or modified corn starch, is a clean label ingredient—as well as an economical and environmentally friendly fat replacer—is good news for processors.
Mayonnaise, salad dressings, sauces, condiments, milk, cream, cheese, yogurt, nutritional beverages, and many desserts are compositionally and structurally heterogeneous materials made up of at least two immiscible liquids (generally oil and water), with one of them being dispersed as fine particles in the other. The fat droplets are enveloped by a protective coating of emulsifier molecules, such as small molecule surfactants, phospholipids, proteins, or polysaccharides.
More than two thirds of mayonnaise—one of the most widely enjoyed sauces/condiments in the world—is made up of fine oil droplets. This, of course, also makes it a high-fat and high-calorie food. Fat replacement by extruded corn flour (also known as pregelatinized starch) in mayonnaise and other formulations can be accomplished by the gradual increase in the number of oil droplets, with a concurrent reduction of their size and proportion in the formulation.
Reduced-fat mayonnaise made with pregelatinized starch possesses the thixotropic behavior (becoming thinner over time) of standard mayonnaise, but also a greater freeze-thaw stability, because the starch traps the free water, diminishing the number of water crystals and, thus, the volume expansion of the aqueous phase.
The replacement of oil by the pregelatinized starch helps retain the oil droplets and prevent separation. This suits makers of the mayonnaise-based salad dressings that are typically frozen for use by delicatessens. In Hampton Creek LLC’s Just Mayo brand of vegan mayonnaise analog, modified food starch and pea protein replace the whole egg and egg yolk used in traditional mayonnaise for a slight reduction in saturated fat content, but a significant reduction in price, and greater freeze-thaw stability.
A combination of different fat replacement strategies is needed to mimic the physicochemical, sensory, and biochemical properties of fat in chocolate. Chocolate is an emulsion-based food valued for its highly specific taste and texture characteristics.
Chocolate makers have had an ongoing challenge with the cost and availability of cocoa butter. High performance inulin with high-molecular weight fructans has been used as a partial substitute for cocoa butter. They have been shown to be adequate for replacing about 5-10% of the fat without appreciably changing the viscosity or the texture of the finished product.
The task of replacing cocoa butter completely, however, is challenging, due to its unique properties. Naturally occurring fats like cocoa butter that are comprised of many triacylglycerides (commonly called triglycerides) melt over a range of temperatures and create a melting profile associated with smoothness, vs. a singular harsh melting point. One of the prized attributes of true chocolate is that its melting point is just a few degrees below the temperature of the human mouth.
The polymorphic nature of cocoa butter, along with multiple temperatures for melting of its constituent fats, combine to affect the texture, sheen, and “snap” of the chocolate. All of these characteristic properties must be considered when blending in other natural fats.
A cocoa butter replacer made of mango kernel oil and palm stearin has been gaining ground in chocolate confectionery for tropical climates because of its low cost and improved heat resistance. Best of all, the blend maintains its fat structure at 99°F, which is above the average melt temperature for cocoa butter (93°F). It is a solution for tempering issues for chocolate manufacturers with distribution in warm climates.
The fatty acid composition and phenolic compounds in mango seed oil (or mango kernel oil) make it particularly desirable for chocolate and compound coating. Mango seed, which makes up almost one-fourth of the weight of the fruit, is a waste product from fruit processing. Mango kernel oil has a triacylglyceride profile similar to that of cocoa butter with palmitic, stearic, and oleic acids as the primary fats.
The standard of identity for chocolate in the US, Canada, and India does not allow for replacement of cocoa fat with vegetable fats. In other countries, however, oils from sources such as mango kernel, even kokum/gurgi, (Garcinia indica) illipe, palm, sal (Shorea robusta), or shea, have been proven acceptable in chocolate confectionery. This includes bittersweet, dark, or milk chocolate, unless they are renamed as “chocolaty” or other like terms.
In Europe, however, up to 5% vegetable fat content other than cocoa butter is allowed in chocolate confectionery. Companies such as Mars Inc. and Nestlé Co. are incorporating them in their UK products such as KitKat and Black Magic Classic Chocolate, respectively, for better shelf-life and affordability in tropical and emerging markets.
The Eyes Have It
The amount, composition, size, interfacial properties, and interactions of fat with other lipids, and with other ingredients, contribute to a food’s optical properties. This affects the visual appeal of foods and beverages. People eat with their eyes before they even take a bite.
Some of the desirable visual physicochemical attributes normally provided by fat droplets can be mimicked by indigestible inorganic substances. For example, titanium dioxide particles often are used to increase the opacity (“whiteness”) of foods. Titanium dioxide has a relatively high refractive index and scatters light strongly. It is an effective whitening agent that can be used to recreate some of the desirable creamy appearance of a product when the fat droplet content is reduced.
This strategy is used to create reduced-calorie and reduced-fat products, such as WhiteWave Foods Co.’s International Delight fat-free creamers. With the same desirable, creamy appearance as their full-fat counterparts, the addition of titanium dioxide (labeled as artificial color) provides the visual cues to the consumer that match similar, full-fat products.
For food manufacturers preferring a “clean” label, titanium dioxide can be replaced with more natural forms of lightening agents, such as biopolymer particles made from proteins or polysaccharides. A combination of tapioca starch and carrageenan is used in WhiteWave’s Silk Soy line of creamers. They provide a creamy opaque appearance, giving an impression that the product contains more fat than it really does.
Carrageenan is a hydrocolloid derived from seaweed and has been used in food for centuries. It’s gained ground in the US since 1995, when it was approved for use in organic products as a natural thickener and stabilizer. It is commonly used as an ingredient in desserts, ice cream and other dairy categories, and also in meat and poultry products, as well as prepared meals and meal replacement drinks.
Research group Innova Market Insights reported that more than half of dairy-based frozen products, and more than a third of chilled desserts and flavored milk products launched between 2010 and late August 2014 included carrageenan as an ingredient for its fat reduction functionality, according to Lu Ann Williams, Innova’s Director of Innovation.
Fat reduction is hardly a piece of cake when it comes to bakery products. Bakery poses some of the most challenging issues for fat replacement. This is partly because of the high content of fat in most baked goods and also due to complex and harsh processing conditions that often involve high-shear mixing, lengthy proofing, and high-temperature baking. To top all of these, consumers expect a long shelflife at ambient temperature and a desirable taste and texture, no matter what.
Bakery product manufacture requires several different steps, and fat almost always plays a different role in each of these steps. Alternative processing technologies can help recreate textures previously developed via fat content.
Methods such as super-heated steam or microwave and convection heating, instead of traditional dry oven heating, can create the desired structure of breads and cakes. Bakers then may turn to the residual fat and sugar for the development of color and characteristic taste.
Fat is incorporated in wheat tortillas to help plasticize the gluten network and reduce the “buckiness” of the dough (when it becomes extremely stiff) and, thereby, its machinability. Removing fat not only makes dough bucky, it also drastically reduces shelflife and eating quality.
Tortilla makers use customized blends of enzymes and emulsifiers to reduce the resiliency of reduced-fat tortilla dough and avoid changes to processing steps, such as plate pressure. These blends also help create a finished product that is just as soft and chewy as a standard flour tortilla.
Hydrocolloids, such as gum Arabic, carrageenan, guar gum, konjac, pectin, and xanthan, have proven to successfully recreate the texture, mouthfeel, and viscosity associated with fat. When used by themselves, or in combinations when formulating reduced-fat baking products, such colloidal systems help disperse the water evenly throughout the system in place of the fat that is dispersed in systems, such as cakes and pastries.
In dry baked products like savory crackers, formulators are discovering hydrocolloid emulsions of either gum Arabic, gellan gum, kappa-carrageenan, methylcellulose, gum karaya, gum tragacanth, guar gum, or modified starches can replace the oil (or sugar solution) applied topically for adhesion of seasonings that are critical for taste.
According to Innova, innovation on the low-fat crackers front has been relatively limited. This, even though purchasers of crackers usually seek them for health-related attributes such as low-calorie, low-fat and high fiber.
Manufacturers stand to benefit from creating such products and showcasing their healthier attributes, especially considering the widespread opinion held by American consumers that crackers are a healthier alternative to chips and other fried snacks.
Just replicating the structure and appearance of the traditional product is not enough. It is the taste, and ultimately the shelflife, that commonly keep customers returning for more. Understanding the role of fat in creating the desired texture in the mouth is the first and crucial step in figuring out reduction of fat invisibly, so as to not deter trial and repeat purchase.
Tribology, the science of interacting surfaces in relative motion (such as in the mouth), is helping formulators explore the impact of fat reduction on eating, and specifically on the brain, in order to better identify alternative ingredients that can replicate the gustatory effects and neurological effects of fat. This is only the beginning of a new frontier where structure, function, and chemistry algorithms will pave the way for new and unlikely replacers for fat.
Some of the techniques derived from tribology are already in practice, with the identification of ingredients that can reproduce the drinking and functional quality of regular cow’s milk in the various plant-based milk analogues.
Manufacturers of soy- and other rice-, almond-, coconut-, cashew-milk products are developing customized emulsifier and stabilizer systems that lend these products, along with refrigerated and frozen desserts made from them, the stability, homogeneity, viscosity and the milk/cream-like mouthfeel. These and other properties have been key in consumer acceptance and loyalty.
The solutions include integrated emulsifier and stabilizer systems made with sunflower and/or soy-derived mono- and diglycerides and hydrocolloids, such as carrageenan and chia gels. These support the correct viscosity, appearance, creaminess, melting resistance, and other textural properties in the beverages, in both chilled and frozen forms.
ConAgra Foods Inc. removes the yolks from whole eggs, traps fat droplets with flavorings and vitamins in a hydrocolloid-rich hydrogel, and disperses the particles in an albumin-rich phase to make its Egg Beaters emulsion-based, yolk-less egg substitute product. The careful chemistry helps reduce the fat and total calorie content of the product without diluting flavor or texture.
Reportedly, the company, with assistance from David McClements, PhD, of the University of Massachusetts, is exploring the potential of hydrogel particles to modulate the texture, flavor, appearance, stability, and satiety of reduced-calorie, emulsion-based prepared foods, such as soups, stews, and sauces.
A number of healthy ingredients, such as oat flour and fiber, are being tested as fat replacers in bakery and processed meat categories. High-lipid algal flour, although rich in lipid content, can be used as a fat replacer, and as egg and dairy replacers, to help alleviate costs of these otherwise expensive and allergenic ingredients in bakery, sauces, beverages, and prepared meals.
Various protein- and polysaccharide-based ingredients have been developed to replace some of the physicochemical and sensory properties normally provided by fats. These ingredients, typically present either as soluble polymers or as colloidal particles, are typically made of indigestible dietary fibers with relatively low-calorie contents. They also can bring added beneficial health effects. Some are even believed to induce greater satiety than fats.
Protein-based biopolymers, such as gelatin, are hydrophilic, water-soluble molecules that act as effective thickening agents. They provide some of the mouthfeel and binding properties of fat.
Several polysaccharides, specifically agar, alginate, carrageenan, locust bean gum, pectin, starch, and xanthan, occupy an effective volume in solution that is significantly greater than the volume of the polymer chains themselves. This is because they trap water molecules and help compensate for some of the textural changes that occur when fat is reduced or removed from formulations.
Alginates and pectins form physical or covalent crosslinks leading to gelation in the presence of calcium, while agar or gelatin coalesce at low temperature. Whey proteins do the same at high temperatures.
This gelling and thickening can compensate for the textural inadequacies stemming from the removal of fat, although they might not adequately compensate for other changes in food properties that occur when fats are removed, such as changes in appearance, mouthfeel, or final flavor profile.
Let’s Get Small
Particle size plays an important role in fat replacement. Colloidal biopolymer-based ingredients in the range of about 100 nanometers to 100 micrometers can simulate some of the desirable physicochemical and sensory attributes normally provided by fat droplets.
First, they increase the viscosity or gel strength of aqueous solutions and, therefore, compensate for alterations in texture caused by fat reduction. Second, they scatter light and thus compensate for the loss of creaminess that can occur upon fat reduction. Third, they can simulate some of the mouthfeel characteristics normally associated with the interaction of fat globules with the tongue and oral cavity. Finally, they can prevent creaming or sedimentation of fat droplets and other ingredients due to their ability to increase the rheology of the aqueous phase.
Protein microspheres with dimensions similar to those of fat droplets can be formed through controlled aggregation of globular proteins after thermal denaturation. Protein microspheres have been used as fat replacers in the development of numerous reduced-fat products, including cheese, ice cream, and yogurt.
Other structural design principles can be used to create specific frameworks in foods to mimic some of the desirable physicochemical, sensory, and physiologic attributes normally associated with fat droplets (e.g., creaminess, richness, satiety, and satiation). These include coating droplets with substances, such as surfactants and dietary fibers, to alter their digestibility and thus their biologic fate within the gastrointestinal tract. Coatings or hydrogel particles slow lipid digestion in the stomach and small intestine, and help induce satiety through the ileal brake mechanism.
Forming microclusters of droplets by inducing droplet flocculation either inside or outside of the human body can lead to a higher viscosity than that of non-flocculated fats in full-fat products. This makes it possible to replicate the textural properties of full-fat counterparts in lower fat dressings, sauces, and mayonnaise. Clustered or aggregated fat droplets also help induce satiety because of their higher viscosity and slow-moving properties in the g.i. tract.
Fat droplets also may be combined with other kinds of colloidal particles—e.g., biopolymer particles, inorganic particles, or air bubbles—to form reduced-fat products that have almost the same physicochemical and sensory attributes similar to high-fat products.
The multifaceted role of fats in food products is a double-edged sword for formulators and consumers. There are a number of different solutions, but no single ingredient can serve as a “slam-dunk” for all of the functions of fat in any product.
Fortunately, advances in ingredient processing technologies is opening the way to design high-quality, reduced-fat products with improved physicochemical, sensory, and biologic properties—without promoting passive overconsumption of foods.
Increased interest in vegetarian products is creating opportunity for plant-based fat replacers. Product developers are discovering chia seed gel can be a highly effective replacer for gelatin as a stabilizer, thickening agent, or emulsifying agent in frozen food products and across other food categories. The mucilaginous outer layer of chia seeds comprises 5-6% of the seed and, once extracted, can absorb 27 times its weight in water, upon hydration.
Chia seed gel is largely polysaccharide, with about 58% crude fiber, and has good water-binding and oil-holding capacity, as well as viscosity, emulsion activity, and freeze-thaw stability. It also prevents sugar crystallization in frozen dairy products like ice cream. Its health halo, especially, is making it a good replacement for guar gum which, of late, is being diverted for use in the hydraulic fracking industry.
Chalk Up Another One
Controlling calcium content and pH can help enhance the texture of reduced-fat sauces and desserts. Research recently presented at the National Meeting of the American Chemical Society showed that as much as 10% fat could be reduced in desserts, dressing and sauce applications simply by controlling the pH and calcium content, so as to clump fat droplets and trap water inside these clumps to make the sauce have the look, feel and even flavor of a full-fat sauce.