Inulin and that "gut" feeling: inulin, a prebiotic typically found in dairy yogurts to enhance calcium absorption, also can provide moisture in meat substitutes and trade spaces with carbohydrates to supplement dietary fiber

Prepared Foods, July, 2004 by Marcia A. Wade

Before inulin found fame on the U.S. low-carb circuit, it was making regular appearances on the ingredient labels of Stonyfield Farm (Londonderry, N.H.) products and other dairy manufacturers who nourish their probiotics with prebiotic fibers.

Over a span of five years, products by Stonyfield Farm have evolved to include prebiotic inulin in the company's entire line of yogurt and cultured soy products. "Our objective is to continue to provide as many healthy components as possible, through yogurt and cultured products, without sacrificing their quality," says Kasi Reddy, vice president of R&D and quality assurance at Stonyfield Farm.

Stonyfield's yogurts contain six live and active yogurt and probiotic cultures, which include Bifidobacteria. Inulin selectively stimulates the growth of this beneficial microflora, creating the ideal symbiotic yogurt products. "We are big advocates of symbiotic products," says Reddy. "Inulin has a perfect synergy with the probiotic bacteria we use."

Symbiotic food products contain not only health-promoting microorganisms but also the prebiotic fibers that selectively stimulate the growth of lactic acid bacteria. "The health of the large intestine is generated almost exclusively by fermentable fibers (like inulin) that act as a food source for the health-promoting bacteria," concurs Bryan Tungland, vice president of scientific and regulatory affairs for a global inulin supplier.

The relationship between inulin and bifidobacteria results in the production of short-chain fatty acids (SCFA), which creates a low-pH environment in the digestive system and helps with calcium and magnesium absorption, explains Reddy. This low-pH environment restricts the growth of disease-causing bacteria in the digestive system.

"Stonyfield's launch of Yo Baby drinkable yogurts with inulin has been a huge success," states Mark Izzo, director of science and technology at another global inulin supplier. Of late, more U.S. products containing inulin, like those at Stonyfield Farms, also have assumed the challenge to make calcium absorption efficient in the gut. Both launched within the last year, Tropicana Smoothies (Bradenton, Fla.) and Yoplait Nouriche (General Mills, Minneapolis) also contain inulin for similar purposes.

Fermentable dietary fibers, in general, set the stage for the entire health of the human body. The fermentation of inulin produces high levels of propionic acid, the primary SCFA used by the liver to reduce serum triglycerides and serum cholesterol in the blood. "Not only does calcium absorption take place in the large intestine, but 65% to 70% of our immunity is located in our large intestine," informs Tungland. In addition, colorectal health provides a preventive mechanism for autoimmune re-expression.

The USDA allows for structure function claims provided an efficacious dose of inulin is consumed based on clinical or literature references and inulin is a part of the nutritional make up of the food. "Some of the structure function claims that could be made with inulin include, 'helps promote the growth of bifida bacteria;' 'helps promote healthy digestion;' and 'helps maintain healthy cholesterol levels,'" says Tungland. "With the exception of structure function claims regarding calcium absorption, for which higher inulin levels would be needed, most of the structure function claims about inulin fall into the 5g/day category," says Tungland.

The Right Identity

However, inulin has seen a burst of popularity in the U.S. because of its functional properties that affect texture, body and mouthfeel. Many of those textural properties are based on the size of the inulin chain length. Inulin is a nondigestable fiber culled from a chicory root by a hot water extraction process, and then filtered based on chain length.

"One of the misconceptions that a lot of people have about inulin is that inulin, fructo-oligosaccharide (FOS) and oligofructose are all inulin," says Robert Veghte, a business manager at a specialty fiber blend supplier. "They are right to a point, but there are differences between the products. You may be able to get away with using one product in one application, but you may need to use another in a different application."

The difference between inulin and oligofructose is the degree of polymerization. "The correct inulin must be chosen for the food system the manufacturer is working in," says Izzo. With or without a glucose terminal, inulin can consist of linked fructose molecule chains ranging from two to five fructose molecules, all the way up to about 50 to 60 molecules. Standard inulin chains average at about 15 molecules. Long-chain inulin and standard inulin work well in applications that use inulin to bind water. It is perceived to convey a fattier mouthfeel than short-chain inulin. The long-chain inulins provide structure, fiber and bulk fill, are able to sustain high temperatures and (depending on the chain lengths) can bind roughly four times more water than short chains.

The shorter chain length version of inulin, FOS is anything with a degree of polymerization (DP) shorter than 10. FOS comes in two forms created in two different ways. It naturally can be isolated from chicory root and then enzymatically hydrolyzed to shorter chain lengths. Alternatively, several single fructose molecules can be polymerized enzymatically to produce FOS. "The short-chain inulins provide humectant properties and elasticity when used with hydrocolloids like xanthan gum," explains Tungland. Also known as oligofructose, or short-chain fructo-oligosaccharides, shorter FOS chains are sweeter and more soluble. In meats, medium-chain length inulin can represent properties of both long- and short- chain inulin.