Resistance is not futile (where starch is concerned)

Pasta can be made with resistant starch,
reducing carbs to less than 6 g per serving.

By Frances Katz, Senior Technical Editor

They’re starches, but they don’t always act like starches, especially where digestibility is concerned. Resistant starches (RS) behave much like ordinary starch but, because they are not easily digested, they may be assigned zero calories in foods in some cases. And of special interest in the current dieting trend, they help foods carry a reduced carbohydrate label.

“RS is of increasing interest as a food ingredient. Unlike common dietary fiber sources, RS does not hold much water and, thus may be a preferred fiber source for use in low moisture products such as cookies and crackers,” Kansas State University researchers Paul Seib and Kyungsoo Woo wrote in a patent application, which was granted in 1999. “Also, RS is free of a gritty mouthfeel, and unlike traditional fiber sources does not significantly alter flavor and textural properties of foods. Those characteristics can improve the processing and quality of foods such as baked and extruded products when RS is added. Furthermore, RS is measured as dietary fiber, and may be assigned zero calories.”

NOTE TO PLANT OPS Because water-holding capacity of resistant starches is usually lower than most other starches, moving foods around the plant -- whether mixing, pumping, or shaping products -- may require a little more power, especially if the food is a relatively low-moisture product. Also, browning on surfaces is likely to be less apparent, so baking ovens for breads may need a different temperature setting. Higher solids cause heat penetration differences in canned foods. Don’t assume that changing a starch won’t change the processing parameters. But there may be plus sides, too: Changes in the water activity of the finished foods may permit a reduction in preservatives.

In other words, it can be considered fiber for labeling purposes, but acts more like starch for manufacturing purposes.

However, shearing, mixing, and heating may change the amount of starch that remains resistant to digestion. So it’s necessary to analyze the end-food products as they are ready for use by the consumer, notes a research director of a major food manufacturing company, which is evaluating the various available resistant starch products in different foods.

The company is careful about regulations, and diligent about the science that provides labeling back-up. Officials are concerned about the consumer’s perception that Big Food could confuse them by changing the message every few years.

“First we take out the fat and increase the carbohydrates, then we take out the carbohydrates and add protein, while the consumer gains more weight,” notes the scientist, who prefers to remain anonymous. “We have to make sure we have the science right, and our communication to the consumer needs to be clear and consistent. We’re developing a position on RS, but it’s too soon to say where and when we might use these ingredients. But they are unique, and may be very useful, especially if we find a way to communicate the value of the foods to the consumer.”

Twenty years of interest

Early mentions of resistant starch usually set the phrase off with quotation marks. The phrase started appearing sometime around 1982, with high levels of interest at the Flair-Flow Europe workshop on resistant starch in Crete in 1991, at which a number of papers were presented. These papers discussed the digestibility of RS, fermentation and the effect of this material on blood fats and bile acids in the colon, as well as testing methods. As a result, resistant starch was primarily a European subject of discussion for most of the 1980s.

But by the early 1990s, the U.S. Dept. of Agriculture was looking into resistant starch, and its major supply, high-amylose corn starch, was being studied by researcher Kay Behall. Behall fed healthy subjects food products made from high-amylose starches, including muffins, bread, and corn flakes. She found subjects who ate the high-amylose diet had changed insulin-producing patterns and lower serum cholesterol.

Research on the subject has been under way at the Beltsville Human Nutrition Research Center for some 27 years. This work includes the earliest and longest human study feeding high-amylose starch as the primary starch source, approximately half of the total carbohydrates in the diet.

Labeling issues have matched nutritional and functional issues in interest. The American Assn. of Cereal Chemists has launched an Ad Hoc Glycemic (Net) Carbohydrate Definition Committee to develop a science-based definition of glycemic carbohydrates. At the same time, National Starch has filed a citizen’s petition to modify carbohydrate content on food labels. National Starch wants fiber content to be listed independently and excluded from the “total carbohydrate” declaration on nutritional labels.

The designation for fiber, which includes National’s high-amylose products, should be outside the carbohydrate designation on the Nutrition Facts Panel to better correlate with label statements in Europe and the rest of the world, according to Rhonda Witwer, the development manager for nutrition at National Starch (www.resistantstarch.com). “These products test as fiber. Clinical studies clearly show the RS1, RS2 and RS3 types of resistant starches behave as fiber,” she says.