Food Product Design: Health/Nutrition - June 2005 - Focus on Fiber

June 2005

Focus on Fiber

By Karen GrenusContributing Editor

Since the first man ate his first plant, fiber has been a part of the human diet. In the United States, our shift away from whole grains, fruits and vegetables has left us deficient of a nutrient that has been shown to reduce heart disease, obesity and certain cancers. As the effects of dietary fiber on health are studied, the food industry has the opportunity to provide fiber-fortified products that allow consumers to eat healthier without making a major change to their habits.

Does the body good We all grew up with the understanding that roughage keeps us regular. Those with decades of dieting under their belts also know that eating an extra-large portion of vegetables does not leave much room for cake. Beyond the benefits of laxation and satiety, recent research has shown that dietary fiber lowers cholesterol, slows absorption of nutrients into the blood stream and supports a healthy environment in the gut. As a result, fiber consumption has a profound effect on our health and longevity.

The daily value (DV) for dietary fiber is 25 grams for a 2,000-calorie diet, and 30 grams for a 2,500-calorie diet. However, according to the Harvard School of Public Health, Boston, the average American consumes 14 to 15 grams of dietary fiber a day. Those following low-carbohydrate diets are at a greater deficit since the sources of fiber, fruits, vegetables and whole grains are limited.

The Department of Health and Human Services and USDA jointly publish the Dietary Guidelines for Americans every five years. The 2005 edition was released this past January and emphasizes dietary fiber and fiber-rich foods, such as whole grains, fruits and vegetables. Citing fiber's positive effects on coronary heart disease, laxation and possibly type 2 diabetes, the new guidelines recommend consuming 14 grams of dietary fiber for every 1,000 calories. In their 2002 publication of dietary reference intakes, the Food and Nutrition Board (FNB) of the Institute of Medicine of the National Academies, Washington, D.C., recommends that men under 50 consume 38 grams of total fiber per day, and that women under 50 consume 25 grams of fiber per day.

By definition, human enzymes do not digest dietary fiber. Their health benefits are dictated by how they behave in the gut. According to the National Fiber Council, Los Angeles, soluble fibers, such as gums and pectin, form gels in the stomach which can slow the adsorption of some nutrients through the small intestine, while water-insoluble fibers, such as cellulose, hemicellulose and lignin, move through the digestive system largely intact. As will be seen, the term "fiber" encompasses a wide variety of ingredients. To make specific claims about the activity of a fiber ingredient in the body requires clinical studies on that particular ingredient.

The American Dietetic Association (ADA) published its position on the health implications of dietary fiber in the July 2002 issue of the Journal of the American Dietetic Association. ADA explained that fiber, which is not fully fermented in the intestine, increases stool weight due to the presence of the fiber, the water associated with it and additional bacteria produced. This, in turn, not only relieves constipation, but also is used to address problems such as diverticulosis.

Visualizing fiber as a giant sponge greatly underrepresents its effect on gut health. Much of the ADA's discussion revolved around more-recent studies. By increasing the viscosity in the small intestine, soluble fibers such as beta-glucan interfere with bile-acid absorption. The liver pulls cholesterol from the blood to replace the lost acid. The position paper also discusses a slowing in the synthesis of cholesterol as a result of some soluble fibers. Clinical studies of individual fiber ingredients have also shown increased calcium absorption, reduced glycemic response and an improvement in gut health, including the possible reduction of some cancers.

A single fiber ingredient can provide a variety of nutritional benefits. For example, "Fibrim® soy fiber, in clinical studies, has demonstrated physiological response typical of soluble fibers, with associated health benefits including satiety, energy sustentation, cholesterol reduction, gut health and mineral retention," says Keith Thomas, director of new business development, The Solae Company, St. Louis. "This fiber also demonstrates the insoluble benefits of laxation, intestinal health and colon health."

Looking up the definition Beyond a commonality in nutrition, dietary fibers range from hydrocolloids to sweeteners, and from components of whole grains to highly refined products. As suppliers create more products to allow for the fortification of foods without altering them, the definition of fiber is expanding, as well. The FNB and AACC International, St. Paul, MN, have proposed definitions that include nontraditional sources of fiber (for a thorough analysis of the definitions of dietary fiber, see "Dietary Fiber: A New Beginning?" by Ronald C. Deis, Ph.D., in the Dec. 2001 issue of Food Product Design).

The most widely accepted definition of dietary fiber in the food industry is that put forth by AACC. The definition is based on the function of the ingredient in the body: "Dietary fiber is 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. Dietary fibers promote beneficial physiological effects include laxation, and/or blood cholesterol attenuation, and/or blood glucose attenuation."

In 2001, the FNB proposed the following definition, creating a category for fibers that are isolated from the source or synthesized: 1. Dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants. 2. Added fiber consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. Total fiber, then, is the sum of dietary fiber and added fiber.

Title 21 of the Code of Federal Regulations (CFR) mandates that a value for dietary fiber be part of the nutritional statement. Giving a value for soluble fiber is voluntary, except when making a health claim around soluble fiber. Labeling insoluble fiber is handled the same way. Different approved methods from AOAC International, Gaithersburg, MD can determine the actual amount of fiber, soluble or insoluble. Using appropriate methods ensures the quantification of all fiber ingredients.

Staking a claim Health claims are very attractive ways to differentiate products containing fiber ingredients from their neighbors on the shelf. FDA allows for a food product to be labeled an excellent source of fiber at 20% or more of the DV per reference amount, and a good source of fiber at 10% to 19% of the DV per reference amount. That translates into 5 or more grams of fiber to qualify as an excellent source, and 2½ to 5 grams of fiber for a good source.

Several FDA-approved health claims associated with fiber ingredients also exist. For example, 21 CFR 101.76 relates "good-source" fiber-containing grain products (that are also low in fat and unfortified), fruits and vegetables to the reduction of some types of cancers. Similarly, 21 CFR 101.77 talks about the soluble fiber in the same products and carries a statement about the reduction of heart disease. The products, without fortification, must be low in fat, cholesterol and saturated fat and contain at least 0.6 grams of soluble fiber. Manufacturers can make a more-specific health claim for foods that contain the soluble fiber, beta-glucan, from oat or psyllium husk. This claim involves coronary heart disease and requires 0.75 grams of soluble fiber from oat ingredients or 1.7 grams of soluble fiber from psyllium husk.

Beyond FDA-approved health claims are health-related statements that are allowed on the product label. Those claims are specific to individual fiber ingredients and are supported by clinical studies.

Great grains Foods containing at least 51% whole grain and a minimum dietary-fiber level qualify for an FDA-authorized claim stating that whole-grain foods may reduce the risk of heart disease and some cancers. The AACC definition states, "Whole grains shall consist of the intact, ground, cracked or flaked caryopsis, whose principal anatomical components -- the starchy endosperm, germ and bran -- are present in the same relative proportions as they exist in the intact caryopsis." The composition of grains and their products can be found in the USDA National Nutrient Database (www.nal.usda.gov/fnic /foodcomp/search).

Wheat bran, the outer layer of the kernel, makes up roughly 14% of the kernel weight. Most of the fiber in the wheat bran is insoluble. The pericarp of the corn, or bran, makes up 5% of the kernel and is rich in soluble and insoluble fiber. The USDA Agricultural Research Service holds a patent on a hemicellulose-rich gum derived from corn fiber.

The soluble fiber beta-glucan has boosted the popularity of oat products over the last few years. To qualify for the health claim, oat bran must contain at least 5.5% beta-glucan, and rolled oats and whole oat flour must contain at least 4% beta-glucan.

Beta-glucan concentrate provides the health benefits to products not suited for the inclusion of oats or bran. "Oats typically have anywhere from 3% to 4% beta-glucan while the Natureal(TM) products have up to 20% beta-glucan," says Linda C. Douglas, Ph.D., R.D., scientific affairs manager, GTC Nutrition, Golden, CO. "The process concentrates the beta-glucan through dry milling while preserving the whole-grain characteristics, such as proteins and lignans." Therefore, she says, this ingredient can deliver the health benefits of beta-glucan at lower inclusion rates and improve stability when compared to regular oats.

Cellulose, hemicellulose, pectin and lignin are plant-cell-wall materials that function as dietary fibers. Product designers can incorporate cell-wall components into a food system as fruit or vegetable pieces, powders, or fiber. However, these fibers are not interchangeable, warns Jit Ang, executive vice president of research and development, International Fiber Corporation in North Tonawanda, NY.

"When we talk about fiber, we are really talking about a very large classification of different compounds or chemicals," says Ang. "For example, the majority of what we call cellulose is really an alpha-cellulose compound, but there is also a significant amount, anywhere from 8% to 10%, of hemicellulose. Hemicellulose is also a fiber; it is just chemically different from cellulose. The functionality, or the performance, of the fiber that you are going to add into the food system is going to be very dependent upon the makeup of the fiber. Just as important is the structure and physical property of the fiber, which is primarily dependent on processing."

Ang explains that the resulting size of the fiber, as well as the process employed, will impact the texture of the fiber in the final product. Larger fiber lengths are employed for adding structure to baked products, while the shorter fiber lengths are used for smoother mouthfeel. "In cases where smoothness and creaminess are important, we would recommend a bamboo fiber," he says. "Even if they are the same particle size and similar in fiber length, and so on, the inherent properties of bamboo fiber make it a lot smoother, because bamboo fibers are typically very thin and very flexible." Bamboo fiber in soup or sauce applications will act as an opacifier, making the product visually more attractive, as in a low-fat or no-fat product where the opacity due to an emulsion has been lost.

Different plant fibers function differently in a system. "CreaFibe(TM) fibers are like minute straws that, once added to a mix distribute, fill and hold liquid while creating a three-dimensional lattice," says Sarah Schut, market manager, CreaFill Fibers Corporation, Chestertown, MD. "Unlike gluten or some soluble fibers, these fiber products link through a weak hydrogen bonding, adding characteristics like strength and moisture retention while of course being free of calories." In that light, "key attributes to consider are water/oil binding of the fiber and the structural improvement and finished product enhancements being sought by the formulator," she says.

Apple fiber is derived from the leftover pulp after juice is removed from apples. Doug Webster, technical service manager, Tree Top Inc., Selah, WA, says that apple fiber can be used in baked goods by replacing 3% of the flour to achieve a product that bakes well and has the functional and nutritional benefits of added fiber. "Apple fiber has the ability to readily bind free water, minimizing weep or moisture loss during processing and storage. This function alone makes apple fiber a great ingredient in baked goods, fruit-based confections, as well as sauces, gravies and dressings. One often-overlooked benefit of apple fiber is its ability to perform as an anticaking agent when used at 1% addition to sticky inclusions, such as dried fruits."

According to the California Raisin Marketing Board, Fresno, raisins contain 5.3% dietary fiber, including inulin. Raisins can be incorporated whole, or in the form of a paste, to add color, sweetness and humectancy. Raisin paste not only has applications in cereal and bakery, but also dairy products, such as sundae-type ice cream.

Other common sources of plant-based fiber include cottonseed, wheat, oat, psyllium husk and citrus. Cost, fiber content, mouthfeel and texture, color and opacity, water and oil binding, and flavor determine the selection. "When making a food product, the formulator is dealing with a number of natural ingredients, and we believe it's essential for our customers to have a reliable raw material not subject to fluctuations" in quality, advises Schut.

"Cellulose is probably the purest form of insoluble fiber you can find," states Ang. Cellulose fiber is derived from plant materials, and while widely used as a fiber ingredient, is also available in forms that provide different product functionalities. Microcrystalline cellulose (MCC) uses only the crystalline areas of the cellulose fiber and forms a heat- and freeze/ thaw-stable gel. Other derivatives of cellulose are carboxymethylcellulose (CMC) and methylcellulose (MC). CMC is used as a viscosifier, and MC has the property of thermogelation.

Some fiber and cellulose blends in good-for-you products can lend fortification. For example, one new blend is intended for use in baked applications where the fiber is replacing flour. "As you reduce the amount of flour in the bread, you are also reducing the amount of the enrichment itself," explains Ang. "The NutraFiber(TM) would have the equivalent enrichment value, so when you make the final low-carb or high-fiber bread product, the final bread product is not reduced in enrichment." The company can help product designers custom-blend cellulose and fiber ingredients with vitamins and/or minerals to add application-specific fortification levels.

Fiber from fructose polymers Inulin is a carbohydrate that occurs naturally in many fruits and vegetables, including chicory, onions, garlic and artichokes. According to Hilary Hursh, food and nutrition scientist, Orafti Active Food Ingredients, Malvern, PA: "Inulin and oligofructose are types of all-natural dietary fibers extracted from the chicory root. The difference between inulin and oligofructose is that inulin is a broad term that encompasses any polymer of fructose units from 2 to 60. Oligofructose is a more-specific term for the shorter chain, from 2 fructose units to 10." Oligofructose is also known as fructooligosaccharide, or FOS.

The fructose units are joined with a beta (1,2) linkage, making them indigestible, and therefore function as a soluble dietary fiber (typically 87% to 96% fiber). The wide range of chain length of the inulin ingredients results in a broad spectrum of properties. "We typically recommend the smaller-chain oligofructose for sugarlike functionally," says Hursh. "The longer-chain inulin is recommended for general fortification. Raftiline® HP, a longer-chain inulin, can be used as a fat replacer."

Hursh says that as a sugar replacer, FOS contributes the bulk of sugar, as well as much as the same functionality, such as browning. Inulin ingredients range from no sweetness to 30% of the sweetness of sugar and work well in combination with high-intensity sweeteners. She adds that inulin can help mask off-notes from high-intensity sweeteners or added proteins, as well as enhancing flavors like caramel and chocolate.

Inulin can also provide textural benefits to products. "Our product does not have a negative impact on bowl life as some other fibers do," says Hursh. "Inulin products help keep bars softer over their shelf life. The HP inulin has been used in low-fat table-spread and cheese-spread applications, helping to give a creamy mouthfeel."

Formulating with inulin allows for health claims beyond the FDA-approved fiber claims. "We have clinically shown that our products help to boost the body's absorption of calcium," notes Hursh. "A lot of people are interested in making a calcium-absorption claim on their label. Digestive health claims can be made for inulin and oligofructose as prebiotic fibers."

Inulin products are well suited for a wide range of products. The only caution is when formulating low-pH products, such as fruit juices. "There is a possibility of the inulin breaking down into sugar molecules at low pH," Hursh explains. "For most products, that is not a concern." Refrigeration is suggested on a case-by-case basis for these applications depending upon the pH and shelf life of the product. More information on inulin ingredients is available at www.inulinplaza.com.

Roxlor International, Wilmington DE, supplies blends of inulin and FOS with sweetening systems, allowing for the replacement of sugar without the need for additional sweeteners. The company also has products available that are up to 20 times as sweet as sugar. "We use the fibers as a carrying system because we want to incorporate all of the health benefits of the products," says Robert H. Veghte, product manager. "We have created fiber-based products that combine the health benefits of soluble, prebiotic fiber, but are easy to use and add to an application because they already contain the sweetness needed for sugar replacement."

Sending an FOS As described above, the chain length of the FOS determines the sweetness and texture of the ingredient. "Short-chain fructooligosaccharides, scFOS(TM), are obtained from cane or beet sugar through a patented process that attaches fructose molecules to a glucose unit. The degree of polymerization varies from two to four fructose molecules attached," says Douglas.

The scFOS impact flavor. "NutraFlora has a slightly sweet flavor profile that enhances the native flavor of the application, helping to mask off-notes associated with high-intensity sweeteners and soy products," Douglas says. "The positive heat of solution of NutraFlora makes it an ideal ingredient to be used in combination with polyols to reduce the cooling effect."

Multifunctional hydrocolloids Traditionally, food gums have been used to improve the textural attributes of products. As soluble dietary fibers, hydrocolloids have also found a niche in fiber-fortified products. Product designers sometimes select these ingredients for low, instead of high, viscosity to allow for higher levels of inclusion and higher fiber levels in the finished product.

"When we talk about gum, we think automatically about high viscosity and gelling agents," says Sebastien Baray, technical manager, Colloides Naturels Inc., Bridgewater, NJ. "Acacia gum, compared to any other polysaccharide on the market, has a much lower viscosity, due mainly to its highly branched structure." An acacia gum from the company is guaranteed to contain 90% soluble fiber on a dry basis.

Baray describes acacia gum as having a highly branched structure that is difficult to hydrolyze. This structure makes the gum able to withstand extreme processing and storage conditions. The ingredient is also suited for use in natural and organic products. "The main interest is that Fibregum(TM) is an all-natural product; the gum is GMO-free and organic and the processing is natural," says Baray. "We get the purified form through a process involving the addition of water and energy. We do not use any chemical or enzymatic material."

Baray notes that acacia gum has been widely used in snack products as a processing aid, acting as a lubricant during extrusion and lowering the energy requirement. He adds that it can also improve the shelf life and texture of baked products and can supplement already-existing insoluble fiber.

Processors can also create a low-viscosity soluble fiber from a high-viscosity hydrocolloid. Partially hydrolyzed guar gum offers the health benefits of soluble fiber while having the functional properties that allow it to be used at fortification levels.

Ingredients that have been exclusive to health foods are crossing over to mainstream. Jocelyn Mathern, R.D., technical specialist at Acatris Inc., Minneapolis, says that a new grade of fenugreek extract (85% total, 75% soluble, fiber) is being released for use in food products. "FenuLife(TM) has been selected over other sources of fiber in applications where its health benefits are of importance, such as maintaining blood-sugar health and improving satiety in a product," she says.

Picking polydextrose Polydextrose, a 1 calorie/gram bulking agent that consists of 90% fiber, can be used in similar fashion to the hydrocolloids. The nondigestible polysaccharide consists of randomly cross-linked glucose. It is highly soluble and doesn't greatly affect viscosity or flavor. In addition to bulk, polydextrose also contributes texture, particularly in applications that incorporate sugar, flour or fat replacement. Polydextrose acts as a prebiotic and has recently gained approval for labeling as a soluble dietary fiber.

Litesse® polydextrose is manufactured by Danisco Sweeteners, Ltd., Ardsley, NY, from polydextrose, and offers improved flavor and stability over the original polydextrose.

Hard to resist The human body digests nonresistant forms of starch and maltodextrin, providing 4 kcal per gram and a glycemic response. However, processors create resistant starch and maltodextrin ingredients from starch that resist digestion. Their exact functional and nutritional characteristics will depend upon both the source material and the process.

Stan Andrews, Ph.D., manager, bakery ingredient applications, ADM, Decatur, IL, notes that the company produces a digestion-resistant maltodextrin through a proprietary heat and enzyme hydrolysis of cornstarch. "Like maltodextrin, it provides very low viscosity and high clarity, very little flavor impact and very low sweetness," explains Neil Widlak, director of business and product development, ADM.

Andrews notes that these qualities make Fibersol-2(TM) a good choice for fiber fortification in almost any application. As an example, he notes that in a bakery product, the ingredient can be incorporated into the icing, filling, dough systems and glazes as a source of soluble fiber. He says that this digestion-resistant maltodextrin is resistant to heat, acid and salt and requires little to no adjustments in formulation and process when added to bakery products.

There are four classifications of resistant starch (a discussion can be found on www.carbohydratenutrition.com, a website from National Starch Food Innovation, Bridgewater, NJ). RS1 is physically inaccessible, such as starch protected by the seed hull. RS2 starch is granular, but resists digestion due to crystallinity. RS3 starch has been broken apart and the chains of starch have been crystallized. Starch that is chemically modified to resist digestion is classified as RS4. The source of the starch, the classification and the process will dictate the functional and nutritional properties of the product.

Unlike most other insoluble fibers, resistant starch has a low water-holding capacity. This lets product designers substitute the ingredient for flour in bakery applications while maintaining a desirable color and texture. Clinical studies of the digestion of Hi-maize® RS2 resistant starch from National Starch have indicated benefits in the area of gut health. Studies cited by the company reveal that the fermentation of this ingredient results in a high level of butyrate relative to the other acids created. Butyrate is a biomarker for colon health and has been associated with lower incidence of colon cancer and some tumors.

"Resistant starch lowers the glycemic (blood sugar) and insulinemic (blood insulin) impact of foods when used as a flour replacement," says Rhonda Witwer, business development manager, nutrition, National Starch. "It also has been shown to increase insulin sensitivity in healthy individuals. Insulin resistance is a major biomarker for satiety, diabetes, heart disease, obesity and certain types of cancer. Thus, the health implications of insulin sensitivity are tremendous."

Formulating with fiber Ang provides a good starting point when choosing a fiber. "There are really two ways of looking at using fibers in a food system," he says. "One is for fortification purposes to give a high fiber content or reduce the calorie content of the food. Just as important is a second way that fibers are used, strictly for a functional reason that normally has nothing to do with high fiber or low calorie." He adds that it is very possible to add more than one fiber to a product if both function and fortification are required.

"Key attributes to consider are water and/or oil binding of the fiber and the structural improvement and finished product enhancements being sought by the formulator," says Schut. The nutritional requirements will direct the level of fiber, insoluble versus soluble fiber and the addition of ingredients such as inulin, FOS, oat or psyllium where specific claims are used.

If the goal is fortification, then the impact of the amount of fiber added will need to be the first consideration. For example, in a thin liquid system, resistant maltodextrin, acacia gum, polydextrose and FOS would all be viable alternatives. Further considerations include cost, stability and special requirements such as natural or organic. As with any change in formulation,   effect on mouthfeel, flavor and the appearance of the product need examination.

Kirk O'Donnell, vice president of education, American Institute of Baking, Manhattan, KS, explains the typical need for some adjustment to a dough mix when fiber is added. "For bread, roll, pizza or anything breadlike, bakers will usually add vital wheat gluten," he notes. "As you add more and more of the water and the fiber, you are diluting the gluten. Without added gluten, the product will rise and then fall.

"The big thing is taste and texture," O'Donnell continues. "A lot of times, you pull out the fat and protein and put in fiber and water, your texture is going to be different, as will your taste. Sometimes, there are certain flavors that are carried in the fat of the product, and when you try to replace the fat with fiber and water, you can develop a bit of an aftertaste."

O'Donnell's conclusion rings true for any manufacturer marketing healthy products. "It doesn't take a lot to put it in a mixer and get something that you can cover with a package and sell once," he says, "but getting people to come back and buy it again is the trick."

Karen Grenus, Ph.D., has eight years combined experience in applied research and product development in the area of dry blends for savory applications. She holds a doctorate degree from Purdue University in Agricultural and Biological Engineering.

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