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Functional Fibers


Photo: Gum Technology Corporation

Everyone knows fiber is good for you. Nutritional wisdom advises the importance of adequate bulk or roughage in the diet. Insoluble fiber benefits the digestive system by improving regularity and reducing the risk of colon cancer. Soluble fiber can help moderate blood glucose and reduce cholesterol.

However, food technologists know fiber is more than just a healthful ingredient. Nutritional functionality aside, fibers give food developers tools to bind water, add viscosity and develop structure.

Finding fiber 

As technology has expanded, so has the definition of fiber. AACC International (AACC), St. Paul, MN, broadly defines dietary fiber as “the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Dietary fiber includes polysaccharides, oligosaccharides, lignin and associated plant substances.”

Lore Kolberg, regulatory and scientific affairs manager, Cargill, Inc., Minneapolis, interprets this as: “According to the AACC definition of fiber, I would consider gums, pectin, resistant starches and resistant maltodextrins to be fibers. Maltodextrin is a lightly hydrolyzed starch product. Other (nonresistant) starches and maltodextrins are easily digestible and would not be considered to be fiber.”

Gums, with the exception of microcrystalline cellulose (MCC), are soluble. Other soluble fibers include pectin and polysaccharide fibers, such as inulin. Resistant starches are insoluble, as are functional fibers derived from cellulose, bamboo or cottonseed.

Choosing the appropriate fiber or system of fibers is done a case-by-case basis. Dorothy Peterson, starch development lead, Cargill Texturizing Solutions, Hammond, IN, recommends evaluating goals in terms of processing challenges, nutritional goals and finished product attributes. “You can create a system that will address all of those,” she says.

Help from hydrocolloids 

Many soluble fibers increase viscosity through their ability to bind water and/or form networks (see Food Product Design’s Dec. 1999 issue, “Special Effects With Gums,” more information on the chemistry behind this effect).

“Typically, soluble fibers can provide better thickening properties without gelling than starch can,” says Jit Ang, executive vice president, International Fiber Corporation, North Tonawanda, NY. “A pudding needs a certain viscosity and a certain type of mouthfeel. If you go for a traditional thickening agent like a starch, to a certain extent, you thicken—and then beyond that, it becomes a gel, which you may not want. Salad dressings are also a very good example. A gum or combination of gums is used for this functionality.”

For many bakery applications Peterson suggests cold-soluble hydrocolloids, such as xanthan or guar gums: “They assist in retaining moisture and adding viscosity to the batter. You need to add the right amount to control the size of the air cells created by the action of the leavening, resulting in better volume and finer texture. They also hold moisture in that product, so that it gives you a perceived moist mouthfeel and also help extend the shelf life of the product so it doesn’t become stale and dry as quickly.”

From a nutritional standpoint, low levels of gums offer a negligible health benefit, adding minimally to the total nutrient declaration because of their generally low use level. As with most things in life, there are exceptions. According to Allen Freed, president and CEO, Gum Technology Corporation, Tucson, AZ, “High doses can be achieved with low-viscosity gums such as gum arabic, talha, and ghatti, as well as some CMCs (carboxymethyl cellulose) and carrageenans.”

And while gum arabic is considered GRAS, its use is limited by FDA. In frostings, 12.4% may be used, 2.5% in gelatins and puddings, and 46.5% in hard candy and cough drops. Still, certain gums can be used singly or in combination to provide a fiber boost. “Lowviscosity gums produce solutions with very thin consistency and can be used to prepare solutions at concentrations as high as 50%,” says Aida Prenzno, laboratory director, Gum Technology Corporation.

Even some highly thickening gums can be used in high doses, depending on the application. “We have a client who manufactures a muffin using gums exclusively for an extremely high dose of fiber,” Freed says. “Since thickening is desired here, gums such as konjac and guar can be used.” Because most gums contain around 90% soluble fiber, even a small amount can make a label impression.

Hydrocolloids can benefit low-calorie products. “The hydrocolloids are going to play more of a functional role in changing some of the negative attributes of some calorically reduced products by adding a little bit more moisture rentention, mouthfeel and shelf life to the products,” says Peterson.

Alginates are cold-soluble and cold-setting. “They provide heatstable and freeze/thaw-stable gels,” George Ayling, global technical service manager, FMC Bioploymer, Philadelphia. “They are used to produce heat-stable bakery fillings and fruit preparations through their synergistic effect with pectin. They are used as thickening and gelling agents in RTE mousse desserts, restructured fruits and meats, bakery creams and ice cream.”

Choosing cellulosics 

MCC makes an excellent choice for frozen products such as ice cream, due to its ability to control ice-crystal growth. “In baked goods, it helps to extend the shelf life by binding moisture,” Prenzo notes. “In whipped toppings, it improves overrun and stabilizes the foam. It is also widely used in low-fat and reduced-fat products to create a stable mouthfeel.”

Typical usage levels for MCC are 0.10% to 3.00%, depending on the application. “Depending on the serving size of the final product, it could be used to prepare an ‘added fiber’ product,” Prenzo says.

MCC is a good source of insoluble fiber. “Depending on whether it is a straight, 100% MCC or a co-processed MCC with other hydrocolloids, they will provide in the mid to high 90% insoluble dietary fiber,” Ayling says. “Functionally, MCC coprocessed with various hydrocolloids —CMC, alginates, guar, pectin—provides a wide variety of functional contributions, based on end-use applications.”

In ice cream, MCC and cellulose gel provides “freeze/thaw stability, heat-shock control, aids in shrinkage control (altitude abuse), replaces milkfat and MSNF (milk solids nonfat), provides a creamy fatlike consistency, and stabilizes overrun and ice-crystal formation,” Ayling says. These functional contributions are also valuable in UHT whipping creams, cream milks and coconut-milk applications.

The MCC/CMC combination also benefits UHT, HTST or retort beverages. “It is extremely effective in providing long-term stabilization of UHT dairy, fortified and/or nutritional dairy or soy, and soy beverages through the three-dimensional matrix that is formed once the product is activated,” Ayling explains.

“One will also see an improvement in mouthfeel, suspension and product flowability. In acidified whey/juice, dairy/juice and soy/juice we have developed a MCC/pectin co-processed product that shows improved suspension and serum separation control in higher-protein-based systems over pectin.”

A combination of MCC and guar is effective in improving the texture and shelf life of nutritional bars. It also adds heat stability in fruit fillings, and provides body, structure, spreadability and foam stability in whipped icings and frostings.

Irresistible starches  

High doses of low-viscosity gums can provide a fiber boost in some applications, but higher-viscosity fibers can help control batter viscosity.
Photo: Gum Technology Corporation

Although most starches are easily digestible, resistant starches are so named for their ability to resist digestion. Four types of resistant starch have been identified: RS1 is so embedded in foods such as seeds, legumes and whole grains that it is physically protected from digestive enzymes. RS2 is an ungelatinized starch that occurs naturally in uncooked potato, bananas and high-amylose corn. RS3 forms in breads, corn flakes and potatoes when they are cooked and then cooled. RS4s are select, chemically modified starches from corn, wheat, tapioca and potato.

Resistant starches are designed to be invisible fiber sources and do not add functional benefits. This makes them ideally suited to reduced-calorie applications.

Resistant starches, particularly the RS4 types, add very low-caloric fiber. “They are primarily all insoluble fiber, which can be subtracted from the overall calorie content of the starch,” says Peterson. “A lot of the new product development that we’re seeing is very much focused on reducing the overall caloric content, as well as fiber enhancement.”

The fiber impact from resistant starches can be significant because they “can be added at relatively high levels, 10% to 15% replacement of the flour,” says Peterson. “When you replace flour, particularly in an item like a bread product, you may need to add more gluten to account for the gluten you’re taking out with the flour.”

Resistant maltodextrin is an RS3. It has very little sweetness and is sometimes used to modify the sweetness and aftertaste of high-intensity sweeteners. It is more stable to Maillard- type browning than a 10 DE maltodextrin.

RS3-type resistant starch maltodextrin can be derived from corn, tapioca, potato, wheat and rice, although high-amylose corn starch and tapioca starch are most common. “The botanical source of the starch, especially its amylose-to-amylopectin ratio has a major contribution in the yield of resistant starch maltodextrin and finished product properties,” says Ody Maningat, Ph.D., vice president of application technology and technical services, MGP Ingredients, Atchison, KS. “Higher amylose content 50% to 70% of starting raw material will result in higher yield of resistant starch, which can be analyzed as dietary fiber by AOAC Method 991.43. Other starch sources with 15% to 25% amylose may result in lower yield of resistant starch and give abnormally low levels of dietary fiber by AOAC Method 991.43. In this case, preference is given to Method AOAC 2002.02 for determining the level of resistant starch.”

Functionally insoluble 

Functional insoluble fibers are designed to be functional, not to be added as a dietary fiber supplement. “If you look through our company product lines, we have many different types of product, but there are only a few that we would say are functional in a sense that they are used in a food product strictly for functionality and not to contribute dietary fiber content,” says Ang. “One cellulose fiber that has been around probably the longest in the industry is Solka-Floc® 900.” This relatively long fiber, manufactured by International Fiber Corporation, North Tonawanda, NY, is uniquely processed, making it different from other fibers. “From a physical standpoint, it doesn’t appear to be like the fibers you use for enhancement or dietary supplement,” he explains. “However, this fiber is very elongated. It is a somewhat flexible fiber. It resembles a natural fiber, more so than other fibers in the market.” 

The choice of a fiber often comes down to fiber length, as well as the plant source. Length would range from perhaps 15 to 100 microns. Most of the time, cellulose is the most-economical. Fibers from cottonseed, wheat or bamboo are more expensive. With the exception of bamboo fiber, there is little difference among the fibers. “The only time that I would choose a bamboo over the other sources of raw materials would be if this is going into a smooth product such as a salad dressing or even a gel-type product where you don’t want any kind of coarseness or grittiness associated with it. Bamboo fillers are smoother,” says Ang. Other than that, it’s strictly a matter of marketing. What would you like to see on your label? How much are you willing to pay for the fibers?”

Long fibers are normally used at low levels in a lot of bakery systems. “In a chemically leavened system, like cakes or brownies, the addition of this fiber at a low level, 0.5% to 1.0% of the formulation, gives a lot more structure,” says Ang. “When you bake the cake, the brownie or the muffin, and as you remove the finished product from the oven, it doesn’t collapse like a normal cake or brownie would. It tends to maintain the air-cell structure within. This is because this longer fiber tends to form a network.” He likens it to the steel rods that form the internal network of a concrete building: “This is what the fibers are doing. They hold the product up so that it doesn’t sag.”

In addition to their use as thickening and gelling agents, most gums contain up to 90% soluble fiber.

Fillings, such as an aerated peanut-butter filling, are another use for longer functional fibers. “Peanut butter is a very dense product and hard to aerate,” says Ang. “By using a fiber like this, you can actually build enough strength into the air bubbles so they stand up.” This allows the aerated filling to be injected into a cake or other bakery product.

These fibers can also replace some of the functions of fat in low-fat products. Fat plays a large role in the emulsification process when air is whipped into the system. “Without fat being present, it is very difficult to introduce air into the system, because the emulsification process would not be there,” explains Ang. “You wouldn’t have the air-bubble formation and the entrapment of air. Functional fibers can often help.”

A reduced-fat or low-calorie pancake typically has a runny batter. Often, starches or gums are used to thicken the batter. However, adding either too much starch or too much gum, while it controls the viscosity of the batter, can create a less-than-desirable effect in the finished product. “Instead of a light and fluffy pancake, it may be gel-like and elastic, or it may be gummy, because gums tend to hold onto a lot of moisture,” Ang cautions. He recommends using a functional fiber in combination with a gum such as xanthan or guar. “We can incorporate low levels of the functional fiber, whether it’s functional cellulose, bamboo or whatever and, in combination with the gum, we can create a very interesting synergistic thickening effect. In this case, you only need a little of both.”

Fried foods might not be considered low-fat or low-calorie, but use of functional fibers can slow the penetration of oil into the product. “We have used functional fibers to build a structural net around the matrix of the food product that we are frying. By using this technology, we are able to significantly reduce the amount of fat in the final fried food.” In a doughnut, fried fish or chicken, these functional fibers provide a barrier that reduces the fat penetration into the food.

Another benefit of using functional fibers in fried foods is more control over the browning reaction. A food that is over-browned is dark and unpleasant looking. This can be a problem when foodservice personnel are multitasking and have a short window to remove the cooked food from the fryer. Fibers can extend the frying window. “The fibers themselves do not brown and can dilute the browning effect,” Ang says.

Short functional fibers are sometimes used in imitation-seafood products (often called surimi) to protect the protein gel during freezing. Normally, cryoprotectants such as sugar or, in some cases, sorbitol are also used for this purpose. With typical usages of up to 8%, the seafood can become too sweet. “Instead of using the traditional long fibers, in this case we recommend a very short fiber that approaches 20 microns. When introduced into the protein gel formulation in partial replacement of either the sucrose, the sorbitol, or both, it can provide the same kind of protecting effect that the traditional cryoprotectant would provide,” Ang says.

In Europe and other parts of the world, using functional fibers in a protein or meat environment is not uncommon. Fibers are used extensively in sausages, meatloaf, pâté, meat and fish pastes. The fibers bind the juices and fat so they aren’t leached out and maintain volume after cooking.

Functional fibers will naturally boost the overall fiber content of the food product, but because they are designed to be used at low levels, this fiber addition is probably not nutritionally significant. “If you are making a cake and you are not adding any additional fibers to enhance the dietary-fiber content of the cake—functional fibers are added for textural and volume enhancements—then, chances are, you will not have enough fiber in the cake to make any fiber claim,” Ang advises. However, if you analyze the cake containing the functional fibers, it will show that it has a higher fiber content than a control cake.

Prebiotic options 

Using certain functional fibers in fried applications helps reduce the amount of fat that penetrates the food and also can modify the amount of browning.

Inulin, an oligosaccharide derived from chicory root, “is an extremely versatile fiber,” says Wade Schmelzer, senior food scientist, Cargill. “Its combination of excellent solubility, low viscosity and flavor profile allow it to be easily formulated into a wide array of food applications.

Inulin can be invisibly incorporated into dairy-based beverages, yogurts, high-protein nutrition bars, and bakery products, such as breads and sweet goods. The ability of inulin to provide a fat-mimetic effect also opens the door on its use in reduced-fat or -calorie desserts, meats or meat analogues. The lower calorie count of inulin can also be extremely useful for the development of calorie-controlled products.” For most food products, 2.5 grams of fiber from inulin per serving is usually a good starting point. On the label, this would allow for a “good source of fiber” claim on qualified products.

Larch arabinogalactan, a naturally occurring dietary fiber with prebiotic benefit, will improve moisture retention and extend shelf life in baked goods. Fat-free tortillas can be made with the addition of 2% larch arabinogalactan based on the weight of the flour. This produces a less-sticky dough and improves handling, while maintaining good flavor and aroma.

Gains with grains 

High-fiber grains can provide benefits, too. Elizabeth Arndt, Ph.D., manager of product development, ConAgra Foods, Inc., Omaha, NE, recommends using selectively bred high-fiber Sustagrain barley to replace 25% of the flour in an 8- inch tortilla to improve the overall nutrition. “This provides 8 grams of whole grain, as well as enough soluble fiber to qualify for the FDA-approved barley soluble fiber specific heart-health claim.” This barley, available as flour, flakes, steel-cut and whole-kernel forms, has nearly twice the fiber of traditional barley. Regular wholegrain barley contains 17% total dietary fiber (TDF) and 5% beta-glucan, while Sustagrain has 30% TDF and 15% beta-glucan.

High-fiber barley can also customize the appearance and texture of pan and artisan-style breads applications, Arndt adds. “Inclusion of the steel-cut in an artisan-style bread lends a chewy, nutlike texture and wholesome appearance to the bread,” she says. This type of barley is a natural fit in hotcereal applications, “ranging from flour for a porridge-type texture, to flakes for a traditional hot cereal texture, to steel-cut for a satisfying chewy texture and hearty appearance.”

Freed recommends oat fiber in applications that might benefit from its water-holding properties. “Oat fibers with low water absorption properties are the best choice for dietary enhancement and can be used up to 6%, depending on the application,” he says.

Certainly, grains fit the layperson’s notion of fiber. They have added bulk and roughage to the earliest diets of man. Today, the food developer has many choices of fiber to enhance finished-product attributes. No doubt, as technology further derives digestive-resistant ingredients from the plant world, the definition of fiber will continue to evolve.

Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at

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