Prepared Foods Exclusive: Defining Dietary Fiber

By Dr. Sakharam Patil

In human and pet nutrition, few issues have captured attention in the way that dietary fiber and functional ingredients have in recent years. Dietary fibers are non-digestible carbohydrates and lignins that are intrinsic and intact in plants, while added fibers consist of isolated, non-digestible carbohydrates which have beneficial physiological effects in human and pet nutrition. Total fiber is then a sum of dietary fibers and added fibers, which together or alone will be referred as dietary fiber (DF).

DF components provide many functional properties depending on the source, processing technologies utilized in their production and their chemical/physical attributes. To complicate the matter further, the polysaccharides that comprise DF in nature are heterogeneous, and their structure-function relationships are difficult to establish. The oligosaccharides derived from polysaccharides or manufactured by fermentation are fairly well defined, making them easier to incorporate into food systems.

DFs have been divided into soluble and insoluble fibers. Functional and physiological characteristics of dietary fibers are largely influenced by their solubility, the source these ingredients are derived from and the type of processing used to produce fiber ingredients.

Humans have consumed fiber sources, such as chia seed, quinoa, wheat and barley, for thousands of years. As reported by Brand-Miller and Holt (1998) in Australia, Aborigines are known to have eaten some 300 different species of fruits, 150 varieties of roots and tubers, and a dizzying number of nuts, seeds and vegetables. Based on the analysis of over 800 of these plant foods, the fiber intake was an estimated 80-130g/day, depending on the contribution of plants to daily energy needs. Similar accounts have been noted in many regions of world, including a 10,000-year-old record from west Texas, showing the region’s natives consumed 150-250g/day of DF from many plant sources.

Today’s food technologist is faced with a myriad of choices among dietary fibers and derived carbohydrates, and many (sometimes conflicting) claims are made regarding the ingredients’ technical functions--such as viscosity, water holding, texture, etc.--and nutritional claims about the digestibility and glycemic index, among others. Formulating a DF ingredient into food products must be performed with a “systems approach” similar to fat-replacement, low-calorie or low-sugar products that have been in the market for quite some time, and some of these approaches are good. The systems approach allows the use of a group of food components to add, reduce or replace the target ingredient into food. In this case, the target ingredient is “adding DF” and its functional nutritional benefit.

Key physiological benefits of DF include: colonic/gut health, prebiotic function fermented in the colon, promoting healthy bacteria, a hypoglycemic lower blood glucose response in diabetes, lowered cholesterol, reducing the risk of CHD (coronary heart disease) and better mineral absorption.

Major DF sources, such as whole grain, cereal brans, fruit fibers (apple, orange, etc.), are widely available and are being incorporated into an increasing number of foods. While numerous sources are available for DF, some of the main sources can be categorized: whole plant, cell-wall material; derivatives such as resistant starches, beta glucans, bioactive NDO (non-digestible oligosaccharides) and hydrocolloids (mostly soluble polysaccharides gums); and soluble CHO derivatives from plant, microbial and other sources. Their common characteristic is they escape digestion in the small intestine and reach the large intestine, where they undergo fermentation; hence, their effect on metabolism and disease regulation are intrinsically linked to their physicochemical properties, as they pass through the gastrointestinal tract.

The future of dietary ingredients will continue to evolve, as more is learned about human physiology and the benefits of such ingredients. In view of insufficient consumption of DF--especially in Western diets--great opportunities remain in developing and marketing foods that can enhance DF levels in diets worldwide.

Cereal grains are major contributors to carbohydrate intake. Altering the carbohydrate quality and DF content of cereal products in the diet likely would have the most tangible effect on gut health and dietary GI (glycemic index). Food developers have a variety of choices and flexibility in choosing cereal products, particularly in the type of grain, degree of refinement and type of processing. Fibers from various sources are also available, as are a range of functional cereal- and carbohydrate-derived functional ingredients. New wheat and barley whole-grain flours--for example, a commercial ingredient with higher fiber content (30% DF) and some of the other nutritional benefits of beta glucan and phytonutrients--have been introduced recently. The challenge for those aiming to produce positive effects on colon health (gut health) is finding an option that can be slowly fermented in the colon, without producing the stomach discomfort commonly caused by the addition of fiber ingredients.

By various reports, generally accepted physiological benefits of dietary fiber can be summarized as below:
· Improvement of colonic function: a generic claim that includes reducing transit time, decreasing constipation, fecal bulking and managing IBS (irritable bowl syndrome).
· Prebiotic: Fermented in lower GI to produce SCFA, reduce colonic pH, enhance probiotic microflora and reduce pathogenic organisms.
· A hypoglycemic effect attributes to high viscosity in the small intestine, increasing resistance to diffusion/absorption and resulting in lower blood glucose and helping to manage diabetes.
· High viscosity, also resulting in a hypocholesterolemic effect, lowering serum CHL (cholesterol) levels and reducing LDL and the risk of CHD.
· Appetite control: satiation and the potential to manage obesity.
· Improve mineral absorption: Ca, Mg & Fe322.

Great opportunities exist in foods that can enhance DF levels in diets worldwide:
* Enhancing DF in diets worldwide will require a combination of solutions, notably developing products, processing and marketing mainstream ingredients cost-effectively to meet cultural/regional needs sustainably.
* Incorporate DF into mainstream ingredients, such as flours with high DF for staples such as baked goods--bread, flat breads (chapaties, pitas, nans, tortillas, etc.).
* Suppliers must focus on sustained, economically cost-effective supply, preferably available locally/regionally. Unless this happens, applications, formulation and mainstream products will not be available.
* Enhance the use of DF as ingredients via soluble/insoluble fibers and oligosaccharides.
* New and effective analytical methods must continuously be developed to support these developments and health claims related to new ingredients and formulations.
* Continue to develop, formulate and market foods that fulfill the consumers’ taste/convenience preferences for local markets. Transfer new technologies for global needs.
* Regulatory agencies must be proactive in developing guidelines, definitions, and appropriate checks and balances to protect consumers confused by the bombardment with new (and sometimes conflicting) information.
* Marketers and formulators must not exploit the consumer desire to improve health by making claims not substantiated by sound science and clinical data.

Sakharam K. Patil, Ph. D is currently a president of Munster, Ind.-based S. K. Patil and Associates, a group which has consulted for small as well as several Fortune 500 food companies. Patil held several positions in India, the Central Caribbean and Europe. His longest tenure was at American Maize/Cerestar, with positions such as director of QA, VP--commercial development, R&D, marketing and VP of technology transfer assignment in Europe. Patil has a bachelor of science from Poona University, M.S. Food Technology, CFTRI, Mysore University from India and a Ph.D. in food/cereal science, Kansas State University. Patil is currently an adjunct professor at the Whistler Center for Carbohydrate Research, Purdue University.  Contact or 219-922-1033.

From the January 18, 2010, Prepared Foods E-dition