Whey protein concentrate offers thickening functionality.

On average we consume only about 15 grams a day of dietary fiber, even though the recommended daily intake is 20 to 35 grams. Studies suggest that adequate levels of fiber can decrease the risk of heart disease, some cancers, diabetes and high blood pressure. One easy way to increase the general population's fiber intake might be to add it to favorite snack foods, which now contain less than 3% fiber.

Until now, adding plant fiber during the sack-making extrusion process has caused undesirable changes in product texture. But by adding dairy proteins such as whey or casein as binders, ingredients hold together better, making for a more acceptable product that may eventually contain as much as 10% fiber.

Scientists at North Carolina State University modified whey protein isolate (WPI) to produce a thickening powder that's stable across a wide range of shear, pH and temperature environments. A protein-based food thickener offers unique nutritional advantages over conventional starch thickening systems, but the higher costs associated with a WPI-derivitized thickener may limit its applications.

The performance of a thickener made using whey protein concentrate (WPC), a cheaper material, is of great interest to whey producers. The objective of North Carolina researchers was to manipulate WPC into an ingredient capable of thickening and stabilizing food systems. Investigators prepared WPC solutions at protein concentrations above the critical gelation point. The solutions were modified using acid hydrolysis, holding them at gelation at temperatures of at least 80 C for more than three hours, then freeze-drying and grinding them to an average particle size of 25 microns.

Upon reconstitution of the powder in deionized water, the shear, pH and temperature dependence as well as solubility and water-holding of the solutions were evaluated. The WPC-derivitized powder exhibited shear-thinning behavior typical for thickened fluids. However, the viscosity did not vary with time, unlike the thixotropic behavior commonly associated with starch-thickened systems.

The powder was stable in pH environments ranging from 3 to 8, and the temperature dependence fluctuated with pH. The scientists were able to modify the WPC to offer thickening functionality similar to that found in starches and hydrocolloids over a wide variety of conditions. In addition, the powder confers the nutritive benefits of protein, creating an ingredient that's useful in fortified beverages, gravies, sauces, pie fillings, malted-milk products and sports drinks.

Further information. Jeff Resch, Department of Food Science, North Carolina State University, NCSU Box 7624, Raleigh, NC 27695; phone: [phone]; email: [e-mail].