Common advice given to those pursuing a healthy diet is to eat more fiber. And it is good advice to follow.
Dietary fiber, which comes in two forms soluble and insoluble, is the parts of fruits, vegetables, whole grains and legumes that the human body cannot digest or absorb. It delivers numerous health benefits beginning with a fuller feeling after eating, which contributes to weight loss. Insoluble fiber doesn’t dissolve in water and is found in foods like wheat bran, nuts and many vegetables. It promotes healthy digestion and bowel movements reducing the risk of diseases of the colon and intestines. Soluble fiber, which does dissolve in water, becomes a gel-like substance during digestion that helps lower blood cholesterol and glucose levels reducing the risk of heart disease, stroke and diabetes. Sources of soluble fiber include oats, legumes and citrus fruits.
Even with so many health benefits, Americans on average consume only 20 to 50 percent of the recommended amount of dietary fiber.The Institute of Medicine of the National Academy of Sciences recommends that men younger than 50 consume 38 grams of dietary fiber per day and men over 51, 30 grams per day. For woman over 50, the recommended amount is 25 grams per day and under 50 it is 21 grams.
“The typical Western diet doesn’t contain much fiber,” commented Guibing Chen, PhD, assistant professor and lead scientist in the Food Engineering, Processing and Packaging lab, a part of NC A&T State University’s Center for Excellence in Postharvest Technologies (CEPHT) located at the NC Research Campus in Kannapolis. “So you need some supplements or enriched foods. But even enriched foods, don’t have that much fiber. If we add too high a percentage of fiber, you get food that doesn’t taste good. People won’t eat it.”
Bringing Bran to the Forefront
That is one of the dietary dilemmas that Chen is addressing- how to increase fiber content while maintaining sensory qualities that appeal to consumers. Chen’s answer is to use mechanical means to enrich foods with bran, the outer coat of a grain that has the highest amount of fiber as well as proteins, vitamins and minerals. Most food processing removes the bran reducing the overall fiber content and nutritional value of many foods. In preliminary research, Chen studied wheat bran. He’s now concentrating on corn bran finding that he can produce higher quality bread with it. Corn bran is higher in fiber than wheat bran, although both brans are good sources of insoluble fiber, iron, antioxidants and vitamins E, A and B.
With a $300,000, three-year grant from the US Department of Agriculture National Institute of Food and Agriculture that begins in September 2012, Chen’s research with corn and wheat bran will get a boost. He’ll work with microfluidization, which is a process that forces an aqueous dispersion of particles through a micro-channel at extremely high speeds resulting in micro-particles that can be used to enrich foods with fiber. Chen’s research shows that the structural changes that occur in wheat bran treated with microfluidization increase the antioxidant activity by as much as three times that of bran that is not treated. How the process will affect corn bran will be determined during the course of Chen’s grant work.
A second part of the grant is to take brans modified with microfluidization and test them in cereals produced using the extrusion process. Many foods like snacks, functional foods, pastas and cereals are manufactured using this process. It involves mixing and heating ingredients in a stationary barrel where tightly fitted screws rotate until the mixture is forced through a die, which determines the product’s size and shape. Chen is experimenting with the percentage of bran he can include in cereal products that will maximize health benefits while maintaining texture and other sensory attributes acceptable to consumers.
A secondary area of research has stemmed from the success in increasing the antioxidant activity of wheat bran through microfluidization. Associate Professor and lead scientist for Functional Foods Shengmin Sang, PhD, who is also at CEPHT, is working to identify and purify specific phytochemicals in wheat bran that are linked to the reduction in the risk of colon cancer. In a study published in May 2011 in Bioorganic and Medicinal Chemistry, Sang found that the compounds 5-alk(en)ylresorcinols are the “major active components in wheat bran (that) inhibit human colon cancer cell growth.” Chen and Sang are planning future research to see if microfluidization will improve the bioavailability of these types of compounds and, in turn, increase their use to prevent diseases like colon cancer
Encapsulating Bioactive Compounds
Even if phytochemical content is enhanced in foods, it still has to be delivered in ways that the human body can maximize. Chen is addressing that dilemma too. He is developing microcapsules using naturally occurring biopolymers such as sodium alginate, pectin and gellan gum. These microcapsules can be used as delivery systems for bioactive compounds to achieve site-specific delivery and controlled release in the human gastrointestinal tract. For example, Sang is researching ginger as a preventative for lung and colon cancers. Microencapsulation technology may be a tool to increase the bioavailability of ginger extract while masking its pungent and spicy flavor so that it can be more palatable in water or other liquids.
Prevention of foodborne illness may be another application of microencapsulation. Leonard Williams, PhD, professor of Food Safety and Microbiology and interim director of CEPHT, and Chen are studying the use of edible coating materials containing microcapsules filled with natural antimicrobial compounds as a preventative film to stop or delay the development of bacterial contamination of food products like fresh-cut fruits.
Chen has yet another area of research involving canned and prepackaged foods. Overall, from fiber to phytochemicals, he is focused on finding solutions to dietary dilemmas.
For more information, visit NC A&T State University Center for Excellence in Postharvest Technologies.