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The average American falls short by nearly 20g per day of the recommended dietary fibre intake. L Steven Young, PhD, surveys the plethora of ingredient sources available today, and explains the costs, functionality and nutritional issues to consider when fortifying foods with dietary fibre

The US Food and Drug Administration and the US Department of Agriculture have clearly stated the importance of dietary fibre to the diet, but neither has directly defined the term ‘dietary fibre’.

The FDA does mandate its inclusion as part of the nutrition label. To paraphrase The Code of Federal Regulations,¹ ‘dietary fibre’ for nutrition-labelling purposes is defined by the methods used to measure it. Further, the code makes it voluntary to list either or both ‘soluble fibre’ and ‘insoluble fibre.’

But what exactly is dietary fibre? Since 1987, no fewer than 20 definitions have been proposed. The most recent are by the American Association of Cereal Chemists in 2000² and the Food and Nutrition Board of the Institute of Medicine, National Academy of Sciences in 2001.³ The exacting detail of these definitions and the background science are quite lengthy. However, to date and after much ongoing debate, neither definition has been adopted for nutrition-labelling purposes. It remains that ‘dietary fibre’ is defined, at least in the US, by officially approved analyses.

From a digestibility perspective, dietary fibre can be defined as the sum total of all carbohydrate polymers greater than degree of polymerization three (ie, three or more monosaccha-rides, or DP 3, in length) that are 1) not digested nor absorbed in the small intestine, 2) partially or totally fermented in the colon, and/or 3) partially or totally excreted in the faeces. This covers a lot of ground and may be too simplistic, but is consistent with most proposed definitions and recognizes the indigestibility of dietary fibre.

Definitions and methods of analysis keep evolving as does ingredient science and technology. Multiple benefits of dietary fibre are assumed. Key functional and nutritional benefits will differ according to the amount and type of dietary fibre to be considered and the specific application. It is the food technologist’s responsibility to understand and manage all key considerations.

The importance of dietary fibre is clearly outlined in Table 1 below, which shows the total number of dietary fibre-related references made on packaged foods in 2005. Such labelling declarations include, but may not be limited to,‘high fibre,’‘low carb,’ ‘no carb,’ ‘low sugar,’ ‘sugar free,’ etc. It is interesting to note that although ‘low carb’ and ‘no carb’ are purely US marketing terms, worldwide references to dietary fibre on packaged foods outpace US references nearly 12 to one.

The reason dietary fibre is of interest is not only is it a key nutrient for good health, but there is also the apparent ‘gap’ between need as expressed as daily value and actual consumption. Most nutritionists agree that adults need to consume a minimum of 25g fibre per day.

Actually, recommendations have been made (National Academy of Sciences) that dietary fibre consumption should be 30-35g per day and in some instances up to 50g per day. As we actually consume only 12-13g dietary fibre per day, the gap between consumption and need is increasing, not decreasing. This puts pressure on food technologists to find dietary fibre ingredients that can easily and benignly be added to foods.

A PLETHORA OF CHOICES
Key considerations include the food that is to be formulated, the amount of dietary fibre to add to the food, the composition and function of dietary fibre-containing ingredients available, and what you want to say about the finished food.

There are more than 60 sources of dietary fibre (Table 2) with more being commercialized daily, so selection of the right ingredient for the right purpose can be daunting. Composition (soluble and insoluble dietary fibre) is critical, as are minor constituents such as sugars, fats/oils, proteins, salts, etc., that could limit utility of any given ingredient (Table 3). Functionality is measured in terms of water binding, flavour, colour and texture of not only the ingredient itself but how that ingredient affects the functionality of the finished food.

Labelling becomes important based on what you want (principal display panel) and need (ingredient listing, nutrition facts panel) to declare. Further, nutritional efficacy can influence the amount and type of dietary fibre to be used as several health claims or structure/function claims may or may not be available for consideration. Finally, as always, economics play a role.

The cost of dietary-fibre ingredients, of course, depends on availability. The per-unit raw-material cost is important, but does not tell the whole story. The cost per unit dietary fibre and the cost per unit of functionality (the real reason the ingredient is being used) of dietary fibre need also be considered. Many times, raw-material costs may seem excessive, but the cost per unit of real functionality may, in fact, be the least-cost option. Care is necessary when considering costs, but extremely critical to success.

Key ingredient functionalities necessary to take into account include colour, flavour, particle size, density, solubility, contribution of food structure, dispersability (or lack thereof), water binding (moisture retention), sugar content, fat content, calorie content, and effect on overall shelf life and acceptability.

In applications, dietary fibre can function to allow formulation of fibre-enhanced foods of all types. ‘Low/no sugar added’ or ‘sugar-free’ foods,‘low/no net’ carbohydrate foods, fat-modified foods, caloric-modified foods, medical foods and various dietary supplements are included. These all can take advantage of the nutritional efficacy of dietary fibre that can typically include one or more of the following:

• Effect on regularity and reduction of certain intestinal diseases, including certain types of cancers
• Effect on healthful intestinal function
  • Effect on maintaining healthful blood sugar (low-glycaemic index, low-glycaemic load)
• Effect on maintaining healthful serum lipids (triglycerides, cholesterol, etc)
• Effect on maintenance of healthful deposition of fat
• Effect on growth of healthful micro flora in the colon. From these effects, implied claims, nutrient content claims, structure/function claims, and a variety of health-related claims may be available to the food technologist. It is important to make sure that scientific evidence is available to support the appropriate claim.

APPLICATION OPTIONS
Applications for dietary fibre can vary from the old to the truly new and novel.

Beverages: Care is necessary when selecting dietary-fibre ingredients for beverages. Dietary fibres for this application most always will be water soluble; however, each must be compatible with the conditions under which the final product is processed, packaged, stored and distributed. If the ingredient is not compatible, expect to see declining dietary-fibre content accompanied by increases in simple sugars; sweetness; and other quality factors such as colour, flavour and viscosity changes. This is true for all applications, not just beverages.

Processed meats: Processed meats are not typical applications for dietary fibre ingredients; however, when control of moisture loss in cooking is necessary, many dietary fibres have great utility. Typically, high water-binding fibres can also add to dry, mealy, grainy texture in the finished meat product so proper selection and use is important.

Cereals: Extruded, flaked or baked cereals are classical application areas for dietary fibre. Colour, texture and water binding make water-insoluble dietary fibres particularly attractive. However, when limits are met that create functional or sensory problems, judicial use of a select water-soluble fibre can help attain total dietary-fibre contents worth promoting.

Snack foods: Fried and baked snacks are also good products to fortify with dietary fibre. As with other applications there are limits to use, typically defined by flavour and colour, and functional limits if the snack item is extruded or not. There are also significant factors to be considered between cold and high-pressure extrusion executions.

Confectionery: Dietary-fibre fortification of hard and soft confections is possible.

Certainly, the cold extrusion of shelf-stable bars or baked confections can limit the amount and type of dietary fibre to consider.

The utility of any given fibre is a function of its flavour, colour, performance and cost; not all fibres are meant for all applications

Miscellaneous applications: The dietary-fibre content of products such as sauces, dressings, soups, etc, can be enhanced simply. Again, use good judgement to select the most effective dietary fibre for the application at hand.

Medical foods, dietary supplements:

The gap between consumption and need makes the delivery of true fibre dietary supplements of great interest. Powders, tablets, capsules, etc, all have utility in offering ways to truly add supplementation to the diet.

MATCHING SCIENCE WITH CLAIMS
Adding dietary fibre to foods is desirable and demand for packaged foods with enhanced dietary-fibre contents is real and sustainable. Claims and opportunities are market and applications dependent.

The utility of any given dietary-fibre ingredient is a function of its flavour, colour, performance and cost. Not all dietary fibres are meant for all applications. Combinations of dietary-fibre ingredients are fine and many times desirable when appropriate to overcome individual limitations of use.

It is critical to match nutrition science to the intended dietary fibre and application of choice. Matching science with the appropriate claim to be made can help a formulator get to the finish line more efficiently and more accurately.

Finally, it is all about flavour and taste. However, matching product features (facts) to consumer benefits (reasons to buy) across the entire intended shelf life of the food is critical to ultimate product development success.

REFERENCES
1 21CFR101.9(c) (6) and 21 CFR 101.9(g) (2)
2 www.aacc.org
3 www.iom.edu

Steven Young, PhD, is principal of Steven Young Worldwide in Houston, Texas, a technical and nontechnical consulting firm specializing in the development and use of novel new food ingredients.
www.stevenyoung.net
Respond: editor@ffnmag.com All correspondence will be forwarded to the author.