Fiber Goes With the Flow

October 1, 2007

15 Min Read
Fiber Goes With the Flow

Photo: Tate & Lyle

Feeling thirsty? In need of quick hydration? Think you could use a long, cool swig from a tall bottle of something refreshing? Then how about a frosty glass of ... fiber?

“When you historically thought of fiber in beverages,” recalls Scott Turowski, technical sales, Sensus America, Monmouth Junction, NJ, “you thought of something that you’d have to drink when you were old.” But that’s beginning to change. “As the population is aging,” he says, “even younger people are starting to recognize fiber’s benefits, and you’re starting to see it more.”

That rising profile has put pressure on the industry to crank out more palatably potable means of fiber delivery, and thanks to their efforts, it’s safe to say that the days of gulping down thick, gritty solutions are gone. Today’s fiber-fortified beverages are better fit to sip with a straw than slurp from a spoon. “Just think of fiber-fortified orange juice,” Turowski suggests. Tropicana’s Pure Premium Essentials packs 3 grams of soluble fiber per 8-oz. serving— about as much as in an actual orange. “We now have the options to fortify these products with fiber,” he notes, “and not affect quality or make a horrible-tasting product.”

As L. Steven Young, principal, Steven Young Worldwide, Houston, and North American technical advisor, Matsutani America, Decatur, IL, says, “By developing processes and analytical techniques that inherently yield fibers with high solubility and no coarseness, graininess or grit; that are low in viscosity, and color- and flavor-free; and that have high thermal and acid stability,” we not only can introduce fiber to all types of beverages, but in some cases even make those beverages better.

Barriers to entry

To understand how much fiber fortification has improved, it helps to understand what made it so challenging in the first place. “The biggest obstacle to the use of fiber in beverages has traditionally been the high viscosity associated with soluble fibers, and the unwanted turbidity in clear beverages,” says Lorraine Niba, business development manager, National Starch Food Innovation, Bridgewater, NJ. Because they’re so hygroscopic, soluble fibers are notorious for sucking up water to a beverage’s textural and visual detriment. Plus, traditional isolation and separation techniques unleash fiber impurities that mar the beverage flavor.

That’s just the rap sheet for soluble fiber. As for insoluble, some industry experts flat-out declared them impractical in beverages. “Because they’re insoluble,” Niba says, “they don’t dissolve in solution, and so tend to precipitate of out the beverage.” Because they, too, are quite hygroscopic, a little can bulk up a drink a few centipoises shy of sludge in no time.

Drinking a better diet

It’s a wonder there was ever any market for fiber-fortified beverages. However, we have made drinking our diets a national pastime. Practical, portable and prep-free, a sports bottle or travel mug full of something fluid has become a symbol of our time— imbibing, one might say, is the new eating.

At the same time, notes Michelle Schwenk, food scientist, Tate & Lyle Americas, Decatur, IL, beverages, as “a major source of calories for the consumer,” are “under a lot of pressure.” Sodas, sugary juices and suspiciously sweet energy drinks “don’t have a lot of redeeming nutritional value,” she says. Even bottled water is taking heat for robbing us of fluoride and cramming landfills full of plastic bottles.

This hasn’t escaped the beverage industry’s attention, which is always eager to make amends with a new functional fluid geared to a thirsty public. “Beverages continue to be the top choice of consumers seeking improved functional products,” says Niba. “And fiber supplementation is now rated even higher than calcium as desirable in products by consumers.”

Those consumers know what’s good for them. For years, researchers have cited epidemiological evidence linking high-fiber, low-fat diets to reduced risks for coronary heart disease, type 2 diabetes and colorectal cancer. As clinical trials continue to fill in the gaps, fiber’s merits become even harder to ignore. Studies associate a drop in cholesterol levels of between 0.5% and 2.0% per gram of soluble fiber eaten daily; a study by the Harvard School of Public Health, Boston, found a 28% reduced risk of developing type 2 diabetes in female subjects who consumed cereal fiber; and research shows that colorectal cancer risk drops 31% for every 13-gram daily increase in fiber (Journal of the American Medical Association, 1997; 227(6):472-477).

Even below the level of disease, fiber works its mojo. By increasing stool bulk and speeding it through the gut, the insoluble fiber in Grandma’s bran flakes is what kept her regular. Moreover, some soluble fibers act as prebiotics, encouraging probiotic intestinal- flora growth to the benefit of overall gut health. By virtue of its sheer volume, both soluble and insoluble fiber increase post-meal satiety and curb hunger to the tune of a 10% decrease in energy intake and a 1.9-lb. weight loss over 3.8 months per extra 14 grams consumed daily (Nutrition Review, 2001; 59(5):129-39).

Yet, as Schwenk points out, “Americans are way under- fibered.” The daily value (DV) for dietary fiber is 25 grams per 2,000 calories. Meanwhile, USDA’s 2005 update of the Dietary Guidelines for Americans raises those stakes even higher, recommending 14 grams per 1,000 calories consumed —or about 28 grams per day. The Chicago-based National Fiber Council (NFC) goes higher still, advocating an ambitious 32-gram daily intake.

Yet, according to the Columbia University Institute of Human Nutrition, New York, the average American doesn’t get even half that much, topping out at between 10 and 15 grams per day.

Beverages to the rescue

When fortifying beverages with fiber, it’s important to take the product’s pH into consideration. Modified, stabilized fibers, such as some dextrins and fructo- oligosaccharides, are not as prone to hydrolysis in low-pH beverage systems as many other ingredients.

By loading fiber into the beverage products that consumers grab anyway, manufacturers bring more fiber fortification to the nation. “We get an outstanding number of requests for fiber samples and for information related to fiber fortification in beverages,” says Niba. “The beverage industry is very interested in learning how to add fiber as a strategy for making label claims.” The challenge, she says, “is to build a level of fiber into their products that allows them to make a strong label claim, and at the same time maintain a product that is acceptable to their core consumers in areas such as taste, texture and sensory quality.”

Ironically, if it weren’t for the technical challenges, there might not be a more amenable medium for fiber fortification than beverages. The Code of Federal Regulations, Title 21, Part 101.54, allows a product to make a “good source” of fiber claim if it’s low in fat and provides at least 10%, or 2.5 grams, of the daily value (DV) for fiber. To make an “excellent source,” “high in” or “rich in” claim, the same product must meet at least 20% of the DV, or 5 grams. Yet, because “serving sizes for beverages are typically large compared to other foods,” Young says, “this allows any given dietary-fiber ingredient to be added at a relatively low percentage use rate and still have less of an impact on sensory attributes.” Consider the typical energy bar. At 2.5 oz., or 70 grams, it doesn’t make nearly as much room for fiber as, say, an 8-oz. (240-gram) serving of milk, or a 12-oz. (340-gram) bottle of energy drink.

FDA rules allow for a prebiotic claim for dextrin-based fiber, notes Niba, “if a product contains one quarter of the effective dose of the fiber per serving.”

Most beverage designers zero in on these levels because they get the job done nutritionally while not generating excessive costs or sensory drawbacks. “Many of our customers, especially in the area of dairy beverages, are looking to add fiber to their products,” says Jenny Diehl, food scientist, TIC Gums, Belcamp, MD, “and most of these customers are asking for a level of 2 to 4 grams of soluble fiber per serving.” Because the ingredients she steers them to, including gum arabic and inulin, also “have very low viscosities, you can us them at a high loading level without seeing a difference from a sensory perspective.”

Indeed, “if properly selected and applied,” Young says, a fiber ingredient can let you “formulate up to 100% of the daily value of dietary fiber—25 grams per 8-oz. serving —and practically not even know it’s there.”

Perhaps the first issue to tackle should be a fiber’s acid stability. “Juices and most shelf-stable beverages have very low pHs,” Niba says. “Fibers, which are made up of complex carbohydrate molecules, are sometimes susceptible to hydrolysis in high-acid, low-pH systems.” The products of that hydrolysis—simple sugars—aren’t particularly perilous, but why fortify with fiber, and say so on your label, only to watch your beverage’s key functional feature decompose after a few weeks on the shelf? As Young cautions, “This can put any beverage at regulatory risk.”

Not all fibers show the same pH sensitivity. Inulin, with its mixed linear beta-2,1-linked fructan polymers and oligomers, is among the more vulnerable. “Inulin does have limitations when it comes to beverage formulation,” Turowski says. “It’s a bit prohibitive in the sense that low-pH, shelf-stable products can be an issue.” However, once pH reaches 4.0 to 4.2 and above, “inulin can be stable in these products at room temperature for a year of shelf life,” he says. Furthermore, pH is a threat “only at ambient temperature. So if you’re talking about refrigerated products, that’s not an issue, and we can start fortifying things, like orange juice, that are at a low pH.”

Modified, stabilized fibers, notes Niba, such as some dextrins and even shorter-chain species of inulin known as fructo-oligosaccharides, “are not as susceptible to low pH.” For example, the controlled acid, heat and enzymatic hydrolysis used to derive digestion resistant maltodextrin (DRM) from corn starch effectively “immunizes” it against acidic beverage conditions, as well as against the heat of retort, hot- fill or aseptic processing.

Those processing rigors are the second concern to address, as “some fibers are not stable to high heat,” Niba says. “Post-process shelf stability is another concern, as some fi- bers will slowly degrade over time in a beverage system.”

But again, many fiber ingredients are surprisingly robust in the face of these conditions. DRM, dextrin-based soluble fiber and soluble corn fiber ingredients can withstand standard beverage processing and storage challenges.

Soluble corn fiber, manufactured using the same method that gives us corn syrup, is an example of just how much the world of fiber ingredients has widened. “It behaves a lot like corn syrup,” Schwenk says. “We’ve always been aware of this small fraction of corn syrup that’s not digestible, and in most corn syrups, manufacturers try to minimize that fraction. But what we’ve done is change the reaction kinetics to maximize it so that now we have a high level of these nondigestible alpha-1,2 and alpha-1,3 bonds in the molecule.” Displaying corn syrup’s viscosity, but nearly none of its sweetness, it adds not only fiber but bulk to beverages, making it a great companion to high-intensity sweeteners in formulations. 

Even better, Schwenk says, “it dissolves just like sugar. It’s soluble at up to 80%, so there are no issues with functionality at a high level.” In fact, she continues, because it’s available as a pumpable liquid, it’s useful for beverage manufacturers already working with liquid HFCS. “You don’t even have to dissolve it because it already is dissolved.” So it hides even in applications as naked as bottled water. “You can’t taste it and you can’t see it and you can’t detect it when you drink it,” she says.

Solving insoluble problems

As its name implies, insoluble fiber doesn’t dissolve. That has put it on blacklists as a beverage ingredient. “You’re going to feel the graininess of it,” Schwenk says. “And you’re going to have to keep it suspended somehow, which typically means that you’re going to need a thick beverage with particles in it, which most people don’t want.”

Not so fast. As Melanie T. Dineen, senior applications technologist, SunOpta Ingredients Group, Bedford, MA, says, “It’s OK for beverages to have texture and body.” It all depends on the beverage. When advising clients curious about insoluble fiber, she says: “What I’ve told people is don’t eliminate it off the bat. Now, if they’re going to ask me, ‘Can I put an insoluble fiber in water?’ I’m going to tell them, honestly, no.” But with the right viscosity and opacity, a beverage can accommodate insoluble fiber.

So, while everyone else was showing—or, rather, hiding —soluble fiber in bottled waters at the latest IFT Food Expo, Dineen and colleagues featured a yogurt-based apricot mango smoothie whose fruit prep paired insoluble oat fiber and red wheat bran with soluble fiber from inulin (as well as from the product’s guar and locust bean gums stabilizers). The smoothie delivered 4 grams of fiber per 8-oz. serving, which easily earned it a good-source claim and fell just short of clinching excellent. More importantly, she says, 

“People loved it.” It wasn’t clear or texture-free, but what smoothie is? In fact, smoothie patrons often appreciate the heft that a little fiber brings. “People like that there’s more texture there,” she says. “It’s not just mango pulp, but fiber, as well. It’s all about getting the right consumer perception —that it’s OK for a smoothie or shake to have some body. You don’t need to have water-thin products.”

Elizabeth Arndt, manager, product development, ConAgra Foods, Omaha, NE, agrees. “Whole-grain ingredients can serve as a fiber source and provide a variety of textures in different beverage types, including instant and ready-to-drink smoothie beverages.” Her company’s Sustagrain® barley, a waxy, hulless variety with 30% or more total dietary fiber, of which 40% is soluble beta-glucan, “can be used in beverages such as instant dry mixes, as an add-in nutritional ingredient in in-store smoothie bars, and in ready-to-drink smoothie beverages.” Various particle sizes and forms let product developers tailor formulations to a target texture. “A very fine flour can provide a smoothie-like texture,” she says. “Coarser flour or flakes can provide pulpiness and a distinctive visual appeal. And finally, coarse granular and steel-cut pieces can be used to provide a satiating, chewy texture, particularly in yogurt-based beverages.”

Even thinner beverages can handle a judicious dose of insoluble fiber, if strategically chosen. How a supplier processes and grinds an insoluble fiber determines its suitability in beverages. “We sell a lot of different types of oat fiber,” Dineen says. “We have some that will make a thicker product vs. some that won’t make a thick product.” Less lignin and hemicellulose in some of the oat fibers make them “softer and more flexible,” she says. But these same fibers also absorb more water, which refocuses the spotlight on textural goals. “Our highest-absorbing fiber,” Dineen says, “at 1%, will work best in a shake. The middle-range fibers are typically for when someone wants less viscosity. These are soft, but they don’t absorb as much water. And we can also grind them finer.”

In fact, Dineen has had “really good success” using softer, flexible fibers in chocolate milk. One 8-oz. serving of the version she developed provides 2.5 grams of fiber from 0.75% and 0.31% oat fiber and inulin, respectively, as well as from hydrocolloid stabilizers and the cocoa itself. “It’s not 100%, and it depends on the cocoa,” she notes, but “I found out that there’s actually a fair amount of fiber in cocoa when I was formulating the chocolate milk.”

Strategic suspension, though, remains critical. “If you don’t want your bottle to have any sediment on the bottom, you have to use some sort of hydrocolloid to keep it suspended,” Dineen says. Suspending insoluble fiber may actually help increase fiber totals, as many hydrocolloids used for suspension—carrageenan, gellan gum and cellulose gels, for example—also assay as fiber. The Chicago-based American Dietetic Association concludes that a normal, mixed diet consists of about two-thirds to three-quarters insoluble fiber, with the rest soluble, so product designers can more closely match this natural balance when they combine a little of both in one beverage formulation.

Granted, cost in use, as well as viscosity, limit how much fiber we can add via hydrocolloid stabilizers. “Usually, if you’re using 0.030% or 0.015% carrageenan, it’s not really contributing too much fiber,” Dineen says. “But a little bit of carrageenan in combination with a soluble fiber and insoluble fiber together make a balanced beverage that has great mouthfeel and the physiological benefits of both soluble and insoluble fiber.”

Hydrocolloid choice rests mainly on formulation and processing conditions. As always, pH factors into the decision. Most dairy-type carrageenans, Dineen says, perform best above a pH of 4.0. “I’ve gone down to 4.4, 4.2 in a juice system, but that’s as low as I have gone.” Heat can be an issue, too. “I’ve had some good results with gellan gum when I’ve just been pasteurizing the product,” she says. “And if your beverage is pasteurized and/or homogenized, you can use carrageenan and CMC. That’s a good combination if you’re making a UHT chocolate milk. They all add to your fiber content, but they’re also keeping your oat fiber or soy fiber in suspension.”

She almost makes it sound easy—not to mention delicious. And that’s what sets this latest generation of fiber-fortified beverages apart. “We’re making them taste good,” Dineen says. “We’re not just throwing in a bunch of ingredients. We’re using superfruits, really good flavor systems—and it tastes good. You’re enjoying it rather than plugging your nose and chugging it down.”

Kimberly J. Decker, a California-based technical writer, has a B.S. in Consumer Food Science with a minor in English from the University of California, Davis. She lives in the San Francisco Bay area, where she enjoys eating and writing about food. You can reach her at [email protected]


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