Moo-ving Toward Fat-Free Dairy Products

Sweetener reduction. Replacing or reducing caloric sweeteners is an obvious calorie-reduction method. However, sweetener reduction can only be a significant method of reducing calories in high-sugar dairy products, mainly ice cream and yogurt. Three high-intensity sweeteners are currently approved for use in the United States:

Aspartame is the best-selling high-intensity sweetener in the United States. It gained acceptance because of its clean and sweet taste, but possesses limited pH and temperature stability, and is low in solubility. However, this is not a problem with dairy products. It was approved last June by the U.S. Food and Drug Administration (FDA) as a general-purpose sweetener.

Acesulfame-K was approved for use in 1988 in 22 food categories, including dairy products. Acesulfame-K and aspartame are synergistic -- a smaller quantity (by weight) of the materials provides the same sweetness when the two are blended.

Saccharin is the oldest U.S.-approved sugar substitute. In the past, questions have surrounded its safety as a food additive, but most researchers believe it has no long-term adverse effects at acceptable intake levels. It might produce a slight "chemical" flavor.

Fructose provides 4 kcal/g, as does sucrose. However, it is 1.6 times as sweet as sucrose and could be used to reduce calories by 35% to 40%, while still providing the same sweetness level.

Bulking agents. These ingredients replace the "bulk" or physical weight/volume removed when a large quantity of caloric sweetener is replaced with a high-intensity sweetener. They also provide texture, viscosity, mouthfeel and other properties. They provide little or no sweetness.

Polydextrose, a low molecular-weight polymer of glucose and sorbitol (with a trace of citric acid), is fairly bland, water soluble and provides only 1 kcal/g. Polydextrose replaces the bulk and absorbs the water normally held by sugar, according to Frances Moppett, marketing manager, Cultor Foods, Groton, CT.

Another ingredient that can provide bulk in dairy products is inulin, a low-calorie (1.0 to 1.5 kcal/g) polysaccharide extracted commercially from chicory root.

Both of these bulking agents also provide some of fat's texturizing properties, and therefore can function as fat-replacers alone, or in combination with other ingredients.

Sugar alcohols. This group of calorie-reduced sweeteners not only replaces bulk, but provides a certain level of sweetness. They have fewer calories (1.6 to 3.0 kcal/g) than carbohydrates, but also are less sweet than sucrose. They can be combined with high-intensity sweeteners and other bulking agents for sugar replacement. Sorbitol has been used for many years, primarily as a humectant and plasticizer, and can be used in dairy products.

Trimming fat

  Reducing the fat in dairy products is probably the best way to reduce calories. At 9 kcal/g, fat has the highest calorie content per gram of any food ingredient. With fat levels ranging from 4% in whole milk to 10% to 15 % and above in ice cream, significant caloric reductions result by reducing fat or replacing it with a lower-calorie ingredient.

  Fat reduction can be performed in a number of different ways:

Use less fat. This is the basis of skim milk and other low-fat milk varieties. Historically, fat was removed, but nothing was added to replace its mouthfeel. The products don't taste the same as full-fat milk, but many consumers accept the differences.

  With other high-moisture dairy products, fat removal usually requires a formula adjustment. It might require increased water plus higher protein, hydrocolloid and/or emulsifier levels. However, the use of an additional fat-replacer or substitute might not be necessary.

Carbohydrate-based fat-replacers. A gel (or sometimes a paste) can be formed from a starch, maltodextrin, dextrin, cellulose or cellulose derivative, hydrocolloid gum or protein.
Calorie reduction then occurs because a 20% to 25% solids gel that provides only 1 kcal/g (or less) replaces a 9 kcal/g fat.

Starches and maltodextrins. Starch-based fat-replacers include conventional unmodified starches (rice starch in particular because of the small size of rice starch granules and the texture of the resulting gel), standard modified food starches (from regular and waxy corn, potato and tapioca), plus some new products made specifically for fat replacement, such as Stellar by A.E. Staley Manufacturing Company, Decatur, IL; and N-Lite by National Starch and Chemical Company, Bridgewater, NJ.

  Maltodextrins, particularly the less converted or lower dextrose-equivalent (DE) products, can replace fat. Low DE products form a "soft-reversible" gel, providing texture and mouthfeel resembling that in a full-fat product.

  A similarity exists in gel-forming properties between the lower DE maltodextrins and some acid-modified starches. Scientists speculate that some of the starch molecules in both are capable of hydrogen bonding and subsequent gel formation. The gel is not firm as with many starches, but soft and fairly easy to reverse and/or deform.

Celluloses. These include microcrystalline celluloses (several of which can form cellulose gels), cellulose derivatives and cellulose fibers. They produce textures ranging from pastes to gels, and provide zero calories.

  Microcrystalline cellulose is derived from cellulose hydrolyzed with acid to dissolve the linear chains, leaving "microcrystalline bundles." Dispersing these bundles in water by using mechanical agitation forms 3-D networks of cellulose chains. The soft, creamy gels closely mimic the mouthfeel of a fat emulsion.

  Many fat-reduced products contain blends of microcrystalline cellulose with carboxymethyl cellulose (CMC), xanthan gum, guar gum and/or maltodextrin. These gels control water and are stable over a wide temperature range. They stabilize foams, important in ice cream, by thickening the water phase between air cells and increasing film strength.

  Cellulose derivatives are chemically modified celluloses. They include CMC (in several viscosity grades), methyl cellulose, and hydroxypropyl methyl cellulose. They thicken and add viscosity, provide freeze/thaw resistance, reduce syneresis, and stabilize emulsions and foams.

  Cellulose fibers, in various forms, have been used as a zero-calorie bulking agent.

Hydrocolloid gums. This group includes natural plant-based gums (such as carrageenan, pectin and locust bean) and microbial gums (such as xanthan). Very low levels, usually less than 1%, provide the desired viscosity or texture. Gums are commonly used in many full-fat dairy products, such as ice cream, so increasing levels for fat replacement might limit any new problems. Many gums are not metabolized, providing zero calories.

  Guar and locust bean are galactomannon gums that function as thickeners. Locust gum interacts with xanthan gum to give a soft gel and with kappa-carrageenan to form a rigid gel. This thermally reversible gel is elastic and reduces syneresis.

  Carrageenans are a family of sulfated polysaccharides that includes kappa, iota and lambda carrageenan. The first two gums form strong gels; the latter forms more of a thick paste or dispersion. Combining starch and carrageenans provides a range of interesting textures -- from a smooth paste to a cuttable gel. Kappa- and iota-carrageenan form an ionic network with casein, a milk protein. They form a strong gel at levels as low as 0.2%. This gel improves emulsion and freeze/thaw stability and controls melting properties of frozen dairy products. Gels of kappa- and iota-carrageenan are stable at pH 3.5 to 4.0, making them useful in yogurt/fruit blends.

  Alginate polymers contain alternating guluronic and mannuronic acids. They form gels with multivalent cations, like calcium and aluminum. In ice cream, they improve freeze/thaw stability and stabilize the fat emulsion.

  Pectins, a family of gums derived from fruit sources, consist primarily of galacturonic acid partially esterified with methoxyl groups. High (above 50%) methoxyl and low (below 50 %) methoxyl pectins exist. The latter react more readily with calcium. Pectins also react with proteins at pH levels below their isoelectric point. They will precipitate gelatin under acidic pH, but not in presence of salts.

  Xanthan gum, a polysaccharide produced by bacterial fermentation, provides extremely high viscosity, effective over a wide temperature range. It produces a somewhat long, slimy texture, so is frequently used in combination with other gums. It can suspend solids, such as cocoa in chocolate milk.

Reduced calorie fats. This fairly small group includes salatrim (sold by New York-based Cultor Food Service under the brand name "Benefat," which has licensed the product from Parsippany, NJ-based Nabisco Inc.) and Cincinnati-based Procter & Gamble Company's Caprenin. They are both triglycerides, but the fatty-acid groups have been altered to compounds not metabolized like natural fats. The caloric content of both products is 5 kcal/g.

  The materials have functionality similar to cocoa butter and have found some use in chocolate and chocolate coatings. To date, these materials have been not used as dairy fat-replacers.

  Olestra, the only zero-calorie fat substitute, has received FDA approval for savory snacks, but not dairy applications.

Proteins. Ordinary proteins can function as fat-replacers; others have been specially processed to give them extra water-binding properties. All the protein-based materials form colloidal gels, giving them body and mouthfeel of a fat emulsion. Proteins used in dairy applications include:

Gelatin can be used in frozen dairy desserts to help maintain air cells and overrun, and to slow meltdown. It provides a soft gel, and helps prevent syneresis in yogurt.

Simplesse® is Deerfield, IL-based NutraSweet/Kelco's brand name for its line of microparticulated whey proteins. It works not only in frozen desserts, but also has been approved in butter spreads, cheese spreads, cream cheeses, sour cream and yogurt. Simplesse is normally a 42% solids gel, but also is available in dry forms.

Dairy-Lo, a whole-whey product using controlled denaturation, was developed by Ault Foods in Canada and is marketed in the United States by Cultor Foods. It can be used at 2% to 5% in frozen dairy products. For labeling purposes, it is classified as a whey protein concentrate.

LiPro is a lipophilized (physically modified) protein containing 99% protein and 1% natural fatty acid. It functions like an emulsifier/stabilizer and improves the texture of dairy products.

Reducing program

  With dairy products, several important factors should be considered. "Water management" -- controlling the free and bound water -- must be taken into account. This is easy to solve in high-moisture/low-solids products, such as milk, sour cream or yogurt. However, in a product such as ice cream, water contributes to texture and mouthfeel. Plus, processing, freezing and thawing can affect some ingredients' water-binding properties.

  In addition, it's easier to replace fat mouthfeel in low-fat products, but much more difficult with ice cream and most difficult with cheese. With some products, transition from full-fat to low-fat is easier than transition to no-fat. It should also be noted that fat affects flavor-release and has masking properties.

  "With sugar-free products, you have to work around 'bitter notes' and 'super sweet' tastes coming from the high-intensity sweeteners, plus off-flavors that you might get from the bulking agents," says Kathleen White, senior food technologist, Bush Boake Allen, Montvale, NJ. "However, when fats are replaced, you have a dual problem of replacing mouthfeel, plus reducing the more intense flavors that may result because of masking by the fat. A reformulation of the flavor system has to deal with both issues."

  Fat also can affect other ingredients' functionality. This becomes important with ice cream and frozen yogurt in which other ingredients, such as sweeteners and emulsifiers, are essential components.

Milk (including evaporated and condensed forms). Most reduced-fat milk and evaporated and condensed milks simply go from full-fat milk to skim milk. This changes viscosity and appearance, but most consumers have accepted the differences. However, chocolate milk requires low levels of starch and/or hydrocolloid gums to provide body and suspend solids.  Unflavored skim milk lacks mouthfeel, possesses a thin, watery consistency plus an unappetizing light-blue color. Addressing this, Golden Jersey Products Co., Vero Beach, FL, combines oatrim (the U.S. Department of Agriculture (USDA) oat-based maltodextrin containing (-glucan) and a "super skimming" process to produce a fat-free, cholesterol-free milk. Whole milk skimmed to 0.05 % fat contains Replace (oatrim with a proprietary blend of emulsifiers and stabilizers), followed by pasteurization and homogenization.

  A second product, known as Skim Delux, was developed by Mendenhall Labs, Paris, TN, and entails adding a small amount of cellulose gel to skim milk prior to pasteurization. The process results in skim milk with the viscosity of 2% milk. The company has been licensing the technique to dairy processors for at least two years.

Sour cream, cottage cheese and yogurt. This group consists of similarly composed dairy products using dairy cultures and requiring similar fat-replacement techniques. When fat is reduced in a product, the principal challenge is maintaining texture and flavor of its full-fat counterpart. "It's easier to work with liquid systems, such as yogurt and sour cream, because you already have to deal with managing a lot of water," says Jeff Laurent, marketing manager, National Starch & Chemical Co., Bridgewater, NJ.

  Also, with these products, concern exists that a fat-replacer might affect active cultures. This could affect fermentation rate and overall product quality. It makes sense to measure culture activity by measuring titratable acidity when designing cultured products.

  Hydrocolloid gels typically replace fat by binding water and providing viscosity and mouthfeel. Using starch in combination with one or more gums is common. For example, starch and xanthan gum provide creamy texture to low-fat yogurts. Carrageenan and pectin work at the low pH found in yogurt. Gum agar and gelatin can help bind water and prevent syneresis in yogurt products.

  Blends of gums with starch, emulsifiers, and in some cases, corn syrup solids, will supply emulsification and stabilization (plus required texture in low-fat sour cream, yogurt and cottage cheese), according to Florian Ward, Ph.D., director of R&D, TIC Gums, Belcamp, MD. Lipophilized protein also performs the same functions and has excellent water and fat-holding properties.

  Maltodextrins also can be used in sour cream and yogurt. They provide a soft, reversible gel that mimics the texture and gel character of gelatin and hydrocolloid gums. In yogurt, it imparts a custard-like texture; in sour cream, it maintains body. Satisfactory results can be achieved at levels of 1% to 5% maltodextrin.

Ice cream/frozen yogurt. Calorie reduction in frozen milk products is much more complicated due to a higher fat level: 10% to 12% for regular full-fat ice cream, and 16% to 18% for some premium brands. Other ingredients provide key functionalities to the system, and the addition of fat and sugar replacers might alter their functionality.

  Proteins increase fat-emulsion stability. Emulsifiers reduce emulsion stability by replacing proteins on the fat surface. When aerated, the fat emulsion begins to break down and the fat globules begin to destabilize. The air bubbles forming in the freezing base are stabilized by this partially coalesced fat, producing a smooth texture.

  Ice-crystal formation in ice cream also can be affected by fat-replacement ingredients. To obtain a smooth texture, crystal size must be controlled with mono- and disaccharides and stabilizing polysaccharides.

  Freezing point must be below that of water (0°C). This is controlled by the amount of dissolved molecules in solution. It's increased with more monosaccharides compared to disaccharides. Ice cream has some unfrozen water at the typical serving temperature of -15° to -18°C. Without this unfrozen water, ice cream would be too hard for processing and eating.

  Removing mono- and disaccharides increases the freezing point. Maintaining the freezing point requires replacement with the same number of similarly sized molecules. Soluble bulking agents or polyols can be used for this.

  Adding a product, such as sorbitol (usually less than 2%), helps reduce the freezing point of sugarless ice cream, according to Frances Moppett, marketing manager, Cultor Foods, Groton, CT.

  Reducing carbohydrate sweeteners or fat, and adding carbohydrate- and/or protein-based ingredients, might:

alter the functionality of one or more of the ingredients important in producing a stable air/liquid emulsion (called "misbalancing the formula");

change the solids concentration, and alter the freezing properties and freezing point;

cause excessive viscosity, creating processing and freezing problems; and

add off-flavors or uncover flavors normally masked by fat . (Without fat, flavors come across as being too harsh. Low levels of fat -- 1% to 2% -- might minimize flavor problems.)  Hydrocolloid gums affect a variety of properties of frozen dairy products. Guar and locust bean gums provide viscosity and improve overrun in ice cream. Carrageenan, at concentrations as low as 0.20%, can improve emulsion and freeze/thaw stability. Carrageenan and locust bean are used to control melting properties. Carrageenan, locust bean and guar also act as protective colloids to prevent casein precipitation, or wheying-off, during processing. Alginates also are used in ice cream to improve freeze/thaw and stabilize fat dispersion.

  Cellulose gel (from microcrystalline cellulose) stabilizes foams and improves overrun. It also helps redistribute moisture during freeze/thaw to prevent large ice-crystal formation. The cellulose derivatives act as viscosifiers, reduce syneresis, and provide cling. They also can help stabilize foams and emulsions, improve freeze/thaw, and promote formation of smaller crystals. CMC delays melting of frozen dairy products and improves extrusion of ice cream from the freezer.

  Maltodextrins also have been cited for their utility in ice cream. Oatrim is particularly useful because of its cholesterol-reducing properties. Usage from 2% to 5% has been reported in United States (Patent 5,225,219, G. Inglett to USDA, July 6, 1993).Used in combination with a regular stabilizer, they provide body, mouthfeel and bland flavor in ice cream products.

  Physically modified proteins, Dairy-Lo and Simplesse, have been used in commercial ice creams. The combination of Simplesse and NutraSweet (aspartame) also has been employed in no-fat/no-sugar ice cream and frozen yogurt .

Cheese products. Problems associated with ice cream are aggravated in natural cheese because of higher fat levels (30% to 35%), higher solids levels, the need for cheese cultures, and its dependence on protein structure. A review of the problems associated with fat replacement in cheese, discussed by P.S. Kendstedt, Opta Food Ingredients, Bedford, MA, is summarized below.

Flavor. Removing fat makes all flavors more prominent. Eliminating fat changes the chemistry of the cheese process. When fat is lowered, moisture must be increased to prevent a hard, rubbery texture. This alters protein and salt levels, which alter proteolytic and microbial activities on aging. Residual lactose levels might increase, leading to abnormal fermentations and pH development, and potentially, more off-flavors.

Melting properties. Generally, low-fat cheeses don't melt as readily as full-fat products. During normal melting, fat globules liquefy and cause collapse and melting of the cheese curd. Removing fat makes cheeses tough and chewy, with poor flow properties. Removing fat changes cheese color and appearance. It tends to have a dull surface, which becomes translucent on aging or melting.

Body and texture. Cheese can be thought of as a filled gel -- the fat globules act as a filler, disrupting the protein matrix and forming a more porous structure. Removing fat forms a more compact protein network, resulting in a hard, rubbery product. Solving this problem is not easy. Increasing the moisture content results in a more open matrix and enhanced proteolytic activity, both of which can produce a softer cheese. However, higher moisture might increase proteolysis and modify fermentation, leading to off-flavors and a pasty consistency. Reduced-fat cheese tends to shatter during shredding and the product has a drier, less lubricated texture.
  "Fat reduction is much more successful in processed cheese, dips and spreads,"says Sandra Hughes, dairy segment manager, FMC, Philadelphia, PA. "Current statistics indicate that only 2% of natural cheeses are low-fat compared to 10% for processed cheese and 16% for, specifically, cream cheese. The biggest issue is yield; product yields are usually quite low for low-fat natural cheeses, making them very expensive in the market place."

  Combinations of microcrystalline cellulose and various hydrocolloid gums have been quite successful in reduced-fat cheese products. Carrageenan and microcrystalline cellulose have been combined for fat-free processed cheese and cheese spreads. The amounts of each, plus the type of carrageenan, determines texture, deformability and melting properties of the resulting products. A blend of cellulose and guar gum has been used to provide a drier texture, and reduce stickiness and rubbery/stringy quality.

  Protein-based products also have been successful in cheese applications. Dairy-Lo is used as a fat-replacer in a line of 50% reduced-fat natural cheeses called "Sonoma Lite Jack", produced by Sonoma Cheese Factory, Sonoma, CA. In addition, Kerry ingredients, Beloit, WI, produces a line of milk protein isolates for low-fat cream cheese. They keep the cheese stiff, yet spreadable.

Process solution

  One way to alleviate some of the negative effects of fat-replacers is to combine fat removal with certain process and system changes. A program started at the University of Wisconsin in 1986, with funds provided by the National Dairy Promotion & Research Board and the Wisconsin Milk Marketing Board, found that improved low-fat cheese could be produced by combining regular and adjunct cultures, plus certain process modifications.

  Adjunct cultures were prepared by either heat- or freeze-shocking techniques; these produce cultures that do not produce lactic acid, but retain their other microbiological functions. Combining cultures solved the problem of off-flavors due to lactic-acid overproduction. Work is continuing with the goal of developing several cultures for different cheese types. This approach, combined with the use of fat-replacers, might help in the search for improved low-fat cheese.

High pressure

  A new fat-replacement technology, based on high-pressure steam cooking of starch and soybean oil, was recently developed at the USDA labs in Peoria, IL. Chemists George Fanta and Kenneth Eskins found that after cooking starch and oil together, they obtained a gel that could be easily dried and ground into a powder. The oil did not separate out on further heating or freezing. They reported that by using as little as 2% of this ingredient -- called "Fantesk" -- in a frozen dairy product, a 0.3 %-fat ice milk had the same taste and texture as an 8%-to-10%-fat ice cream. Bedford, MA-based Opta Food Ingredients has obtained an exclusive license on Fantesk, and will be commercially developing the technology.

  More recently, G. Inglett developed a new form of cellulose fiber named "Z-Trim." The material forms a gel with high viscosity and smooth, nonsticky texture, somewhat similar to that made from microcrystalline cellulose. It has zero calories and is reported to be especially useful in cheese-based products. A patent has been applied for, and the invention will be offered for license to commercial developers when the patent has issued.

  The challenges of developing low-cal dairy products are mainly related to texture, mouthfeel and flavor; once these are conquered, the way is paved to a successful new low-calorie product.

Mapping it out

  Food Product Design has presented fairly detailed procedures and suggestions about the various steps required in the product development process, particularly regarding low-calorie foods, most recently in the September 1996 cover story, "Composing Low-Calorie Foods." Several important issues should be emphasized when designing dairy products. A well-conceived map or plan for developing new dairy product is essential:

  Ensure your objectives coincide with marketing objectives. This is important in the low-calorie dairy area, because everyone needs to understand that "no-fat" might not be possible and that "low-" or "reduced-fat" needs to be a viable alternative.

Do your homework. Know the potential ingredients, label requirements and nutritional aspects of potential ingredients.

Contact suppliers. Suppliers will generously offer information about their ingredients, and might have determined typical formulations that can be used as a starting point in your work.

  Don't forget local colleges and universities. Not only do these institutions have libraries for conducting literature searches, they have food-science and dairy-science departments that can provide information and experimental-testing facilities.

  Test and retest. During your experimental program, you need to be confident that:

your laboratory and pilot-plant prototypes are compatible with your production capabilities, or that your new process is going to work with your new product;

you have repeated production of your pilot-plant prototype a sufficient number of times to be sure of the process;

your experimental products have repeatedly passed standard tests for physical and shelf-life properties;

your product has passed an adequate number and level of sensory evaluations.  The final point above means more than just utilizing an in-house panel. Your product doesn't necessarily have to be identical to your full-calorie standard or to your competition. However, the differences you measure must be acceptable within your original objectives.

  Perform not only standard tests for your particular dairy product, but particularly for changes in flavor, texture and mouthfeel. Also, be sure you know what's happening to the new ingredients in your process.

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