Understanding Polydextrose and How It Works

Lengthen shorter chain polymers of different sugars and you get this designer soluble fiber.

By Mark Anthony, Ph.D., Technical Editor

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Glucose is the sugar in our blood that supplies us with energy. When dozens of glucose sugars are linked together, it's called starch. But there are ways glucose units are joined that makes them indigestible, and for some applications that can be a good thing.

We can't derive energy from grass because the glucose sugars that make up the cellulose, which is structurally similar to starch, are linked together by bonds our digestive enzymes cannot break. Cellulose thus passes undigested into the colon where it functions as an insoluble fiber.

In the mid-1960s, Hans Rennhard, a Pfizer Inc. researcher, created a polymer of 89 percent glucose, 10 percent sorbitol and 1 percent citric acid that functioned as a soluble fiber. After patenting in 1973, and FDA approval in 1981, polydextrose was classified as a soluble fiber. Multiple studies have demonstrated its safety and positive effects on digestion.

Yielding only 1 kcal/g, polydextrose has become a multipurpose ingredient helping ingredient manufacturers increase non-dietary fiber content while replacing portions of a product's sugar, starch and fat. This, in turn, helps food and beverage makers create products with reduced calories and lower energy density in a variety of foods, including beverages, cakes, candies, dessert mixes, breakfast cereals, frozen desserts, puddings and dressings. It's also been a boon to low-carb and sugar-free creations.

Commercial polydextrose is available under brand names such as Sta-Lite by Tate & Lyle, Decatur, Ill.; Litesse by Danisco, New Century, Kan., now a division of DuPont Nutrition and Health; and Trimcal from C&H Ingredients, Farington, UK, as well as others.

Last year, Nutrition Reviews published "Dietary fiber type reflects physiological functionality: Comparison of grain fiber, inulin and polydextrose." The authors compared the effects of these different fibers on digestion and various blood parameters. The article compared the physiological effects of three types of dietary fiber with varying compositions, degrees of chemical and structural heterogeneity, origins and physical properties.

There are obvious differences. Grain fiber is chemically heterogeneous. It has both insoluble and soluble fractions, along with associated compounds, each promoting various biological activities. In contrast, inulin and polydextrose are industrial products that must demonstrate their beneficial physiological functions in order to be classified as dietary fiber. Inulin is a soluble fructose polymer that promotes the growth of bifidogenic bacteria and is efficiently fermented by gut microbes. Polydextrose is a soluble non-viscous manmade polymer that is only partially fermented by the gut microbiota.

An important factor drawing the attention of food manufactures to the use of polydextrose in various applications is its simplicity. Here the homogeneity of the compound may work to its advantage over grain fibers in certain applications. Since polydextrose is a synthetic compound, it's not subject to the natural variations that may affect natural products. The taste, described as clean and non-sweet (vis the low calorie content) does not interfere with the flavor of the end product.

High solubility, clarity and rheological properties similar to sucrose make polydextrose versatile enough to add a desirable texture to a variety of liquids, including dairy drinks and yogurts, sauces and dressings, while reducing calories from fat or sugar. Consumers in general do not want to taste the fiber, but are attracted to smoother and richer consistency when it comes to various liquids. Taste and texture are always key concerns when reformulating foods to a health-conscious audience.

The variety of processed foods impacted by polydextrose is matched by the potential for product presentation. As a soluble fiber with the ability to bind water, polydextrose can partially or totally replace sugar, fat or starch in a formulation -- which means it can be presented as reduced fat, reduced sugar, low calorie, or even low glycemic index, depending upon the application and the target audience.

Polydextrose works particularly well in foods that require bulking agents or those that are traditionally sweet or rich in fat. It is able to maintain the texture and mouthfeel that often is lost in the process of removing sugar and fat to reduce calories. This quality is particularly important when replacing fat in confectionaries and baked goods, where mouthfeel can "make or break" a product.

Because polydextrose is only partially metabolized in the human digestive system, it contributes only 25 percent of the calories of sugar (1 kcal/g versus 4 kcal/g) and only 11 percent of the calories of fat (9 kcal/g). It's realistic to achieve at least a 50-percent reduction in kcals with no compromise on taste and eating quality.

Since obesity is the most pressing dietary concern, there is a number of strategies food manufacturers are employing to attract health-conscious consumers. Polydextrose has allowed manufactures to add fiber and lower calories from sugar and fat without compromising taste or texture.

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