Twin-screw extrusion provides food processors and milling companies with a flexible, profitable mechanism to process products with high fiber and whole grain formulas for breakfast cereals, pasta products, snack foods, co-extruded products, and flat breads.
"In some cases, adding fiber to a dough or batter to meet a claim can change the rheology of the mix due to water absorption," says Chuck Werstack, food applications manager for ADM's research division. He recommends splitting the fiber content between the dough and topical application or mixing both soluble and insoluble fibers. In the case of ADM products, a mix of Fibersol-2 (soluble fiber) and Alpha Cellulose (an insoluble fiber) would be one recommendation.
Although wheat is the most popular grain in bakery formulations, millet, flax and other grains are commonly added to whole- and multi-grain varieties. Oats are, at 10.6 percent, high in beta-glucan, a soluble fiber that qualifies for highly marketable heart-health claims. But, again, soluble fiber is thirsty matter.
Whole grains do not release water with the consistency of refined grains either, compelling processors to play with baking temperatures and times to get their products right. Lower temps and longer bake times may be in order.
Equipment and other challenges
Some fiber -- oat fiber, for example -- can be abrasive to equipment. Wenger's Plattner notes use of whole grains in cereals and extruded snacks can impact machinery.
"Frankly, I'm amazed at how abrasive some fibers can be, especially when you put in a tremendous amount of fiber -- like 20 percent formulation," he says. "That's when you have a real processing issue. Particle size is extremely critical. If you are going to use fiber in an extruded operation, grind it." Fiber is held together by a cellulose-like polymer called lignin (not to be confused with lignan). It is the glue that binds fiber and helps, along with cellulose, to bind plant cells.
"When you mill a lot of fiber sources with lignin, you will beat up your equipment," Best warns. Fiber's lack of functionality in baking applications often demands the addition of gluten to strengthen the mix.
Whole grains and high fiber formulations should be mixed more slowly than formulations with more-refined flour. Less mixing may be required with the fiber's superior water absorption capability, but rapid mixing also opens the door to potential blending error.
Note to R&D
Some of the less obvious fibers and grains may be perfectly suitable replacements for formulations while posing fewer problems, sometimes even advantages, for your processing machinery.
Citrus fiber, for example, mimics fat with its ability to bind water and oil and offers advantages in managing moisture and thickening. It reportedly is effective in pound cake formulations.
While many consumers today love the coarse texture of whole grain products, others continue to associate it with cruder and less tasty products of the past. "By using fine grind whole wheat flour made from white whole wheat, the cell structure of bread and rolls will look more like what we get from white flour," says Charlie Morris, manager of ADM specialty ingredients-bakery.
For those who object to the bran or germ flavor of certain whole grain products, Morris recommends honey or molasses to overcome this flavor hurdle.
For snack and other applications, Chuck Werstack, ADM's food applications manager, recommends edible beans as a great source of fiber. "These beans contain 22 percent fiber and have shown very good results in extruded snacks and crackers."
ADM also has introduced Fibersol-2 to the market to enable processors to reduce the amount of water they need in the formulation.
"It's a soluble fiber that is 90 percent fiber -- very high in fiber -- and does not hold water," says Morris. He claims a 2 percent Fibersol-2 formulation content can help solve the problem and necessitate little formulation adjustment in the bakery process.
Sun-Opta, reportedly the world's largest producer of oat fiber, also offers a fiber derived from okara, the nutritious pulp remaining from soymilk production. Among okara fiber's marketable properties are its neutral flavor and its solubility with water.