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March 1, 1995
Increasing Quality by Reducing Not Replacing Fat
By: Scott Hegenbart
Consumers have sampled the flock of fat-free products currently on the market and have, in many cases, pronounced them unacceptable. Now food designers are finding that they can increase product quality significantly by reducing, rather than eliminating fat. Although it can ease many formulation challenges, creating a low fat product often requires as much effort as developing one that is fat free. In fact, formulating a high quality, reduced-fat product requires that designers make extra efforts at determining critical fat levels and selecting the best-performing fat, in addition to evaluating fat replacing ingredients for the system.Textural hurdles Why are fat-free products such a challenge? For many industry designers, the number one difference in fat-free products is texture. Many features are texture-related, including mouth coating, mouthfeel, dryness, and so on. In bakery foods, for example, removing the fat gives cakes and breads a drier, firmer crumb. Gums and starches - when used as fat mimetics - may alter the texture, making it more gelatinous. Fat also provides structural features that affect texture. Reducing the roll-in shortenings that contribute to flakiness in Danish pastry by only 5% to 10%, for example, causes a noticeable reduction in quality. "Even if the taste is the same, the mouth sensations will be different," says Amna Abboud, Ph.D., senior research scientist, Kraft Food Ingredients, Memphis, TN. "The product won't taste like Danish; it will be more like a coffee cake." Fat also contributes necessary structure to icings. Once fat is removed the designer must replace this structure, as well as the moist, lubricious eating qualities. Structure in salad dressings changes significantly with different fat levels, and the product may no longer adhere to lettuce acceptably when fat is removed. Attempts at correcting such changes often create problems of their own. "When trying to duplicate the lubricity of fat, it's sometimes replaced with sogginess," says Mark Izzo, group leader, bakery and confectionery technology, FMC Corp., Princeton, NJ. "Not only do you wind up with soggy products, you also have problems with moisture retention and migration. "On the other hand, you see some products get too hard," Izzo continues. "When you take the fat out of granola bars and cookies, you have nothing left to interrupt the carbohydrate structure of the food." Eliminating fat also alters flavor, both the flavor imparted by fat and the fat-soluble flavors that the fat is helping to deliver. "Without fat, flavors can be delayed or will release too quickly," says Florian Ward, Ph.D., director of research and development, TIC Gums, Belcamp, MD. Fat also has its own flavor in addition to affecting flavor perception." The flavor of fat-free products often is obscured by off-flavors. Sometimes this is attributed to fat mimetic ingredients. Other times, off-flavors can be contributed by ordinary ingredients whose flavor is no longer being partially masked by the fat. In salad dressing, for example, vinegar will have a much stronger bite. "In bakery and confectionery products, fat is replaced with sugar so the resulting product becomes excessively sweet," says Izzo. "Of ten this is not only because the extra sugar is there, but also because the fat had previously helped to mask the sweetness." The product's appearance - specifically whiteness and opacity - also will change. "When you take fat out of gravies and sauces, they become clear and you lose some of the opacity," says Mike Augustine, manager of food ingredient applications, A.E. Staley, Decatur, IL. "It's not as appealing to look at as a full-fat product."Process complications Difficulties presented by fat free systems don't end with flavor and texture. Processing is difficult with many no-fat products, particularly for bakery systems. Doughs tend to be stickier and will cling to machinery such as mixers, cutting heads and rotary moulder dies. "I have not been able to find anything among all the fat replacers that can replace the lubricating properties of oil with respect to machinery contact," says Scott Sanders, president, Creative Food Consultants, Discovery Bay, CA, who serves as a technical consultant to firms including The California Prune Board. Even regular breads that are fat free are very difficult to produce without oil. Dough sticks to dough dividers, and baked bread won't release from pans and will nearly always crumble during high-speed slicing "It's possible to achieve fat free bread in the lab, but I've not seen it done on a consistent basis in a production environment," says Sanders. "This is one area where you need to go with a reduced-fat product." Emulsified meat products can be just as challenging since fat contributes body and viscosity to the emulsion. "With an ordinary meat emulsion, you can usually pick it up in your hand and hold it upside down. The low-fat products are more like mud," says Dan Putnam, senior applications scientist, Grain Processing Corp., Muscatine, IA. "This can be like trying to stuff soup into a casing. Although modern equipment is better, it still isn't meant for a product with such a low viscosity." In addition to handling difficulties, altered viscosity creates many related quality problems such as those associated with obtaining the desired coverage in an enrober or icing application system. In some cases, reduced-fat products can actually be damaging to processing equipment. "When attempting to make a lower fat peanut spread, de-fatted peanut flour and other nonfat ingredients often are used," says Izzo. "As this goes through the mill, it can overheat from lack of lubrication. The fat often lubricates the product through the processing equipment." Once made, a fat-free product will not have the same shelf life as its full-fat counterpart. The main reason for this has to do with water management and how the flavor and texture change over time. "You're often taking fat out and putting in water to make the water perform like fat," says Augustine. "Anytime you replace an ingredient that isn't affected by water with water, it can create a number of potential problems." Some of these include rapid drying, staling problems, or even microbial problems due to higher water activity.Bottom-line barricades Even in the unlikely event that a food designer can formulate a no-fat product with a perfect flavor profile that runs beautifully in the plant and lasts for the entire target shelf life, a final hurdle remains: how much all this technology will cost. "Even if you formulate a good fat-free or reduced-fat product, the formula you come up with may be just too expensive because most replacing ingredients are more expensive than fat," says Abboud. "Ingredients used to compensate for fat - such as gums and modified starches - add to the cost." Not only are some of the ingredients used in fat-free foods expensive, the equipment necessary to handle them can be costly as well. Adhering a seasoning blend to a snack using a gum in place of an oil, for example, will require the addition of drying equipment to the processing line. "Equipment also must be available to handle and spray the gum slurries," says Ward. "Management must be willing to invest capital, if necessary."A little fat'll do ya Any one of the hurdles presented so far can muck up a fat elimination project. Keep in mind, though, that most products will feature a combination of any or all of these challenges. This is, perhaps, the strongest motivation for adding back some of the fat. "Even a small amount of fat goes a long way toward adding back some of the mouthfeel," says Dolf DeRovira, president, Flavor Dynamics Inc., Somerset, NJ. "One might make an analogy between fat replacement and using potassium chloride to replace salt. Some of the positive effects you get aren't worth the negative contributions." How much fat are we talking about? In many products, the levels range from around 2% to 4% - often low enough to qualify for a reduced- or low-fat claim. Muffins, for example, should exhibit moist crumbliness. Other ingredients can contribute moistness to a fat-free version, but fat is necessary to break up the carbohydrate structure to provide the crumbliness. "Adding just a little bit of fat - maybe 3% or 4% - still allows you to maintain a low-fat claim," says Sanders. "At the same time, it gives the muffins the desired moist crumbliness and crispy surface texture instead of a moist, sticky texture." Ice cream offers another example where a small amount of fat makes a big difference. Here, as little as 2% fat can restore many physical characteristics, such as meltdown, and recreate the expected flavor release. "The quality difference between a 2% low-fat ice cream and a nonfat ice cream is tremendous," says John Wyatt, technical director, Danisco Ingredients, Grindsted Division, Industrial Airport, KS. "Of course, the 2% ice cream still is a significant reduction over the standard-of-identity 10% ice cream." Having 2% fat also can make a difference on the shelf life of products. TIC Gums' Ward compared no fat cookie creme fillings with 2% fat fillings and found a significant improvement in water activity. Again, 2% fat still represents a substantial reduction over the 25% to 35% fat levels common in full-fat cookie cremes. Besides the quality advantages, creating low-fat products might help consumers become incrementally accustomed to lower levels of fat in their foods. This could make products with greater fat reductions seem less different to them. "In many cases, I think processors are moving too fast for consumers to acquire a taste for low- or no-fat products," says Sanders. "Consumers generally dislike products where the salt has been removed, whereas someone on a low salt diet for a long time will find a regular product too salty. I think many consumers will experience something similar as they become more accustomed to the lack of greasiness found in full fat foods."Raising sights on low-fat When creating a reduced-fat food instead of a zero-fat food, the product designer's primary goal is to maximize quality with the minimum amount of fat. The first step in doing this is to determine the product's critical fat level. "Every product has a minimum amount of fat required to provide necessary functionality," says Izzo. "Amounts of fat above this critical level offer diminishing returns." As fat is reduced below the critical level, however, formulating an acceptable product becomes more challenging. In a pie crust, for example, some researchers have found that a fat level of around 16.5% - representing a 50% reduction - is the critical fat level below which quality deterioration due to loss of tenderness and flakiness occurs. The following experimental sequence allows product designers to determine the critical fat level specific to their application. It also provides the opportunity for the designer to observe what role in the formula the fat is playing. "It'll make a lousy product, but do it anyway," says Sanders. "So many people think they know what the fat is doing, but they don't." First, make a batch of the standard, full-fat formula in the lab. Then create an identical batch, but take out all of the fat. Additional water may be necessary, but don't do anything to replace the fat just yet. At this point, the goal is to observe what happens. Next, make subsequent batches at logical intervals - such as 50%, and 25% reductions. "By formulating and observing, it'll become clear where you can leave the fat level and what functionality will need to be enhanced," says Izzo. In some cases, particularly if the minimum possible fat level is required, the designer's observations should be supplemented and confirmed using sensory testing. This might include both descriptive analysis and acceptance testing. "There is a lot of sensory testing involved because the perception of fat cannot be measured," says Ward. "You can measure texture with a texture analyzer, but the perception on the tongue also is important." While sensory panels can be a useful tool when formulating a reduced-fat food, they must be applied carefully to avoid misleading results. In particular, special attention must be paid to screening panelists, training them, and identifying targets when designing the experimental procedure. Panel screening. A common error when selecting sensory panelists for a reduced-fat project is to assume that everyone likes fatty foods. Some people simply do not have the same "fat tooth" as others and can obscure the observations of a panel. For example, a panel may be assigned to determine preference between two products near the critical fat level. Panelists who don't like fat may tend to choose the leaner product even though others would judge it inferior. This situation could make determining the critical fat level from the experimental results more difficult. Panel training. If the goal of sensory testing is to define organoleptic properties, extensive panel training is necessary so that the panelists can provide useful descriptive data. It is possible, on the other hand, to give a preference panel too much training. Results from such a panel would be misleading in that the group no longer consists of objective consumer participants. "Many trained taste panels will tend to repeat exactly what's been said to them," says Grain Processing's Putnam. "If you teach your taste panel that you're looking for a good 3%-fat frank, they'll find it. But it won't necessarily be what consumers want." Identifying targets. Whether or not the panel knows the product being tested is low-fat can affect sensory results. "When testing low-fat franks, a lot of people won't like them until you tell them what they are," says Putnam. "When they know the franks are 3% fat, then they'll say they're quite good." If the goal is to match a full-fat control as closely as possible, don't reveal the fat content to the panelists. This is true when doing either descriptive or acceptance testing. When simply determining the acceptability of a sample with known faults, however, comments from panelists will be more useful if they know the sample is low-fat.Critical adjustments As the functional properties of the formula fat become apparent and the critical fat level is determined, the product designer can then make adjustments to the fat itself to maximize its functionality. This not only improves product quality, but also may allow the designer to lower the total fat level a little more. "As you increasingly reduce the level of fat in a product, many times you place even more severe functional demands on the fat in the formula," says Robert Wainwright, Ph.D., director of research and development, ABITEC Corp., Columbus, OH. Helping the fat meet these demands isn't always easy. "When replacing tropical oils was big, the initial approach was to take a look at its fundamental properties - the melting curve, the melting point, etc. - and simply come up with a non-tropical, non-animal fat that parallels these properties," says Wainwright. "Many times we found that this simply was not the way to go. We're seeing the same sort of outcome when reformulating to reduce fat. There's more to it than just replacing it with lower levels of the same fat." Several ways to maximize fat functionality are possible. The most common consider how the fat is handled, the emulsification system included with the fat, and modifications to the fat itself. Handling refers specifically to products in which fat is part of an emulsion, such as in margarine and salad dressing. Here, the homogenizer can be adjusted to yield smaller droplets. "Making smaller droplets increases the surface area to get better use of the fat you actually have," says Wyatt. "The fat may be at a lower level, but you can have the same profile from an organoleptic or texture standpoint." Many fat systems designed for specific applications contain emulsifiers. The fat and oil supplier may be able to extend the functionality of the fat by altering the emulsification system or by simply increasing the amount of emulsifier present. "Cake shortenings are available with many different emulsification levels," says Frank Kincs, associate director of R&D for bakery/food processors, Bunge Foods, Bradley, IL. "One solution for cakes is to use a shortening with a higher degree of emulsification so you can get the fat to run leaner." The mouthfeel and functionality of the fat also may be enhanced by altering the fat itself. "All fats don't taste as fatty as each other," says DeRovira. "Fats of a certain variety and melting profile can give you more of a fatty feel." Fat and oil suppliers have a multitude of processing methods that can alter the performance of a fat or oil. These include sourcing the oil, hydrogenation, fractionation and interesterification. Combining several such methods in different ways and in different orders allows the fat system to be highly tailored for a specific application. "It is possible to hydrogenate or to couple hydrogenation with fractionation to further tailor the fat and its melting properties in order to obtain a fat that provides specific structure, body and stand up properties," says Wainwright. "These processes also may manipulate the fat to preserve stability, or maybe to provide a moisture barrier." Sophisticated modification processes can even combine less digestible fatty acids to yield fat triglycerides that are lower in calories - such as Procter & Gamble's Caprenin and Nabisco's Salatrim. Such fats would allow the fat used in a reduced-fat formula to at least contribute fewer calories. Recent work in this area of fat processing also is yielding new ways to alter performance. Patents issued to Nabisco in January 1995 describe how the geometry of a cookie can be influenced by introducing a medium-chain fatty acid into a variation of Salatrim. Specifically, the patent describes how this modification produced a cookie with greater height than was possible with either regular Salatrim or shortening. The increased height was unique in that it did not change the spread of the cookie. Ordinarily, obtaining a higher cookie means less spread. Other recent patents also contain interesting developments. Kraft General Foods has taken an approach in which calcium citrate is blended with vegetable oils to influence viscosity and fluidity. This could change a finished product in two ways. First, the oil is capable of building more structure without partial hydrogenation. Next, because the oil isn't all fat, a slight caloric reduction may be possible. With all the potential modifications that exist, it would be easy to send a fats and oils supplier on a wild goose chase. Before asking a company to develop a modified fat, do the homework. Perform the initial reduction without changing the fat. Understand what functional qualities are being compromised and determine formulation objectives. Then work closely with the supplier so this information can be shared. This way, the supplier will be much better equipped to determine how some of the sacrificed functionality could be restored.Going sub-critical At this point in the experimental procedure, the designer should have a good understanding of fat's role in the product as well as a formula with the lowest level of the most highly functional fat possible. For many projects, the formula development will be finished. In other cases, a greater fat reduction will be required in order to obtain a specific label claim, such as "light," or "reduced." Review the potential claims with the marketing department and determine the range of fat allowed based on the desired claim. Sometimes a little more fat may be added back to the formula. Because marketing usually wants the most consumer-appealing claim possible, often a little more fat must be removed. In this situation, though, having identified the critical fat level first will leave designers with fewer deficiencies for which they have to compensate. Cookies, for example, often become too hard below the critical fat level. Some researchers have theorized that this is the result of some interaction between the starch and the protein that doesn't occur when all of the fat is present. "You'll want something that either prevents this interaction or prevents the interaction from forming the hard structure," says Izzo. "Look for ingredients that counteract this by replacing that particular function of fat." Before attempting a major overhaul of the system, look for solutions with basic formula adjustments. If the product requires tenderness, add sugar or adjust the solids profile of the sweetener system. If the product is too runny, use an ordinary starch or gum to build viscosity. In baked products, sometimes changing the flour to something with a different protein content may provide the solution. "You'll often count on emulsifiers a lot more," says Augustine. "These are used at low levels. They help extend the fat and contribute fat-like benefits without adding an excessive fat content." Even with the performance of all the other formula ingredients maximized, the product may lack certain qualities once the desired fat level is reached. Now it's time to look at fat mimetics. Using cookie creme fillings as an example, the formula development thus far may have produced a critical fat level of around 20% to 25%, compared with 30% to 35% typically found in cookie cremes. As the fat level approaches the critical point the creme becomes increasingly thicker, and it forms a powder once the fat level is reduced below the critical point. An emulsifier and a change in sugar granulation may help maintain the desired viscosity and allow the fat to be reduced below the critical point, but further reductions still will yield a powder. "You need some sort of shortening-like liquid material," says Izzo. "If you can't use fat, then you have to use some aqueous-phase components. You may even switch the phases completely - an aqueous phase for a non-aqueous one." As with non-mimetic ingredients, the experiments thus far will leave fewer challenges to be solved and will make selecting and incorporating the right mimetic ingredients easier. The reason for this is that the functional properties of fat already will have been identified. The search for the right mimetic can then be limited to those that provide the functions that are missing. (For more details on formulating with and evaluating fat mimetics, read "Fat Mimetic Evaluation: Paring the Procedure," in the March 1994 issue of Food Product Design.Revisiting production Although it is easy to focus on texture analysis and sensory properties when evaluating reduced-fat foods, remember that lowering fat levels below a product's critical point will affect processing. This is not only inconvenient, but it can be dangerous. Processing low-fat frozen desserts, for instance, will cause occasional burn-on in heat exchangers. The base also will be prone to foaming. "If you get foaming, especially in vat pasteurization, the foam on the top won't be as effectively heated and you may not get a satisfactory kill," says Grain Processing's Putnam. "It also causes a lot of pumping problems if there's a lot of foam in the mix." Compensating for such processing challenges must begin at the formulation stage. In the above example, some type of emulsifier - such as polysorbate 80 or mono- and diglycerides - can usually curb the foaming. Until the project reaches the production trial stage, the results of sensory testing and texture analysis can be helpful in determining a product's processability. Increases in product viscosity, adhesiveness or other common texture and rheological measurements all can indicate a potential processing problem and should be addressed before actually scaling up begins. "Product designers should plan on problems with processing," says Creative Food Consultant's Sanders. "And don't assume that one successful plant trial means everything is going to run fine." Once production trials begin, short production runs may not show the potential long-term effects of running such a dramatically different product. Get into the production facility as soon as possible for as long as possible. "Problems often aren't identified until the product is in full production," says Sanders. "The initial plant trials may not have been perfect, but the production department said the product should work. Then, after a week or so, gaskets are starting to wear out, product is accumulating on bands and causing sanitation problems, and cutting equipment is dull and corroded." Longer trials may demonstrate that a product is a lot more difficult to make than anybody on the project team could possibly have imagined. In the above situation, the maintenance department must quickly create a completely different set of preventive maintenance procedures to accommodate the product. In the meantime, the company already is distributing product for introduction and it's too late to back out because the marketing promotion has already begun. Examples such as this should provide product designers with more than enough motivation to cover their bases regarding production difficulties. Still, don't give up the project if it appears that traditional processes won't work. Some other process technology might be adapted to make the product run, but this might require capital investment. On the other hand, such a change might actually make processing easier. Because a no-fat salad dressing has no fat phase, no emulsion must be formed. Consequently, a homogenizer isn't necessary and the product can be made with ordinary mixing equipment. For many products, a little fat can go a long way toward improving quality and easing manufacturing difficulties. Optimizing product quality with the lowest possible fat levels requires that designers plan experiments logically and make detailed observations. Still, the shear number of reduced-fat products competing for consumers often will make such planning worthwhile.Back to top
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