Consuming dietary fibre is known to be an important part of a healthy diet. Dietary fibre specifically, is thought to reduce a person’s risk for developing heart disease, stroke, high blood-pressure, diabetes, certain cancers and obesity. It is also thought to act positively by lowering blood pressure, controlling blood lipid concentration and promoting good gastrointestinal function.
Many of the foods we eat inherently contain fibre such as whole grain foods, vegetables, fruits, legumes (peas and beans) and nuts. The suggested daily intake of dietary fibre may vary slightly depending on country and the actual amount consumed will inadvertently vary depending on the region.
For example, diets high in whole grains, fruits and vegetables, similar to that in Asia, have a higher content of dietary fibre than diets in Western Europe and the US that may not contain these types of foods in adequate quantities.
In addition, there does appear to be a decline in the global consumption of dietary fibre due to lifestyle changes among people who are eating more processed and ready-to-eat meals. Even eating a diet of fibre-rich foods may not be enough to harness the full health benefits that dietary fibre can offer.
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There has been a type of evolution with regards to dietary fibre in foods in the recent years. Traditionally, dietary fibre could only be consumed as part of the above mentioned natural foods, but technological advances in ingredient processing/production have allowed us to obtain high fibre ingredients by extracting from high fibre foods, chemical processing, or a combination of the two.
This has led to food manufacturers using these high fibre ingredients, not only to increase the fibre content of foods, but in certain cases, to use these high fibre ingredients as partial substitutes for non-nutritive food components like starch, fat and sugar.
A few common types of dietary fibre ingredients currently used in this manner are resistant maltodextrin, polydextrose and inulin. These three fibre ingredients are considered soluble dietary fibre as they are soluble in water and form a gel as they go through the digestion process. These materials are not broken down by digestive enzymes as starch is, for example. These materials also have a lower caloric content than traditional digestible carbohydrates.
Resistant maltodextrin is prepared from the thermal treatment of moistened starch and a trace amount of acid. Any digestible materials are removed from the mixture and the remaining material is purified and then concentrated for use.
This material is very stable to heat and acid, which makes it a good choice for certain processed foods. Studies have shown that around 10 percent of the consumed resistant maltodextrin is digested and absorbed in the small intestine, around 50 percent is fermented in the large intestine and the remaining is excreted.
Aside from being extremely stable, it is considered a ‘user-friendly’ ingredient because of its low viscosity, as well as tasteless and flavourless characteristics. Resistant maltodextrin can be used in low calorie foods as a bulking and texturising agent to achieve a desirable sweetness without an objectionable aftertaste. The caloric value for a certain type of resistant maltodextrin is considered to be around one kcal/g, which is considerably less than that of starch or sugar, which is four kcal/g.
olydextrose, similar to resistant maltodextrin, is commercially prepared and not found in nature. Polydextrose is prepared from the in vacuo thermal treatment of glucose, sorbitol and a trace amount of acid.
This mixture is then purified to yield the pure ingredient. The resulting material, similar to resistant maltodextrin, is very stable to heat and acid, which also makes it a good choice for certain processed foods. Polydextrose resists digestion in the upper gastrointestinal tract and is partially fermented in the colon.
First commercially used in the early 1980s as an aid in reducing calories and fat in some processed foods, it has also been used in the Asia-Pacific region since the mid-80s to enhance the dietary fibre content of foods.
Currently, polydextrose is used to improve the nutritional aspects of foods by being a prebiotic, adding fibre and reducing calories, the glycemic load, sugar and fat. In general, the caloric value of polydextrose is considered to be one kcal/g by most national authorities.
Unlike resistant maltodextrin and polydextrose, inulin is found naturally and has been part of our daily diet. It is present in small quantities in foods such as leeks, onions, garlic, asparagus, wheat, artichokes and bananas. It is also found in a greater quantity in Jerusalem artichoke, dahlia, chicory, and yacon.
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On an industrial scale, inulin can be obtained from the extraction and purification of the aforementioned plants/flowers. The most common sources for industrial processing are chicory, followed by Jerusalem artichoke and dahlia.
Similar to other dietary fibres, inulin is not digested by the enzymes of the human digestive system and induces similar physiological benefits. Like the abovementioned resistant maltodextrin and polydextrose, inulin can be used to purely add fibre to a product, but can also be used to enhance the taste, texture, and smell of processed foods.
Its extreme solubility in water also allows for incorporation into water-based products like drinks, dairy products and table spreads. Inulin is also widely used as a prebiotic in dairy foods. While it has many similarities to that of other soluble dietary fibres, it does have the disadvantage of being susceptible to degradation by heat and acidic conditions.
This potential degradation makes inulin a poor candidate for certain heat processed or acidic foods. Like most soluble dietary fibres, inulin is considered to have a lower caloric contribution than that of digestible carbohydrates. A caloric value of between one and 1.5 kcal/g is generally being used for labelling purposes.
As lifestyles are constantly evolving and becoming more fast-paced, the need for quick, nutritious and healthy meal choices are becoming more evident. Soluble dietary fibre may be the answer to achieve more nutritious meals and also to add fibre to other ‘traditional’ products.
While it seems straightforward to add these ingredients and label them accordingly, food manufacturers must be cautious and well-informed about how to accurately market and label the dietary fibre content of these foods.
The term ‘dietary fibre’ was coined in 1953 and at that time, it was considered to be the non-digestible constituents of plants that make up the plant cell wall, known to include cellulose, hemicellulose and lignin.
The definition has evolved since then and unfortunately, it is different depending on which organisation or regulatory authority you ask. This makes using certain soluble dietary fibre ingredients, including the ones mentioned above, difficult as they may be considered dietary fibre by one group, but not by another.
This also creates the problem of international commerce as a manufacturer must comply with the regulations in the country where the food is sold, and not necessarily where the food is manufactured.
It is advisable to fully understand the regulations and requirements in the country of sale prior to formulating a new product, depending on the reason for formulating a product with fibre. Some reasons to use fibre in a product are: for use as a front-of-package marketing tool to support a health or ‘fibre’ claim; for use as a substitute for other ingredients such as starch, sugar or fat; or to produce a healthier, more marketable food.
If the purpose of fibre fortification is to use that information on the label, then the regulations must be strictly followed. However, if one is only trying to replace a non-nutritive ingredient and is not concerned with the labelling or marketing aspect, then the dietary fibre labelling regulations for the added soluble fibre ingredient may not be as critical.
Prior to formulation, it is necessary to perform research about the labelling regulations for all ingredients, in all countries of sale. If there is ever a doubt, it is best to work directly with the ingredient manufacturers, as they are the experts on those products and should be able to advise on the appropriate course of action.
As new ingredients evolve that boost the nutritional aspects of foods without compromising on taste, regulations will need to evolve as well to keep pace with scientific advancement in food technology.