Summer 2001 Issue — Fruit Based Dietary Fibers
Healthy Ingredients in the Food and Health Industry

Dr Jürgen Fischer

Herbafood Ingredients GmbH, D-14542 Werder, Germany

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Introduction

Organic components of plants which cannot be degraded by human enzymes and thus remain unabsorbed in the small intestine are defined as dietary fibers (DF). Recently, an extended definition was given by the American Association of Chemists (2001), which includes the beneficial physiological effect of dietary fibers. This updated definition reflects the scientifically proved nutritional benefits and importance of dietary fibers in the nutrition. Currently, three physiological effects are included: promotion of laxation and/or blood cholesterol attenuation and/or blood glucose attenuation. This inclusion of benefits clearly shows the meaning of dietary fibers in general but also, that not all types of dietary fibers necessarily have to have the same or all effects. Indeed, this cannot be expected because DF comprise of different substance groups, which fit to the physiological based definition.

Despite the general knowledge about the relation between dietary fiber and health (Southgate and Pension 1983), in industrial nations a big gap exists between the mean daily intake and the recommended daily intake. Most diet recommendations suggest that consumer should increase their dietary fiber intake, especially people that suffer from diseases like obesity, enhanced blood cholesterol level or constipation. However, the question arises, why is the intake of dietary fiber still so low?

One reason surely is the eating habits of "western" consumers: too fat, too sweet, too much refined food.

To alter this, consumers have to change their pattern of consumption towards traditional food with a high content of dietary fiber. However, the acceptance of food based on refined ingredients such as white flour, sugar or fat is higher than that of e.g. whole meal products or grain legumes. Traditional foods rich in dietary fiber tended to be hard-textured, dry or sandy and often difficult to chew specially for elderly people.

Another way towards an improved supply with DF is to change the composition of food. A key point to be successful on the market with DF-enriched food is to have ingredients that do not alter the hedonic and textural properties of food negatively. Especially "lifestyle oriented consumers" want to enjoy their meals and snacks. Although they are aware of the importance of healthy eating they don't want to be reminded to eat "healthy" such as in case of classic cereal bran.

Fruit based dietary fibers

Using tailor-made fruit derived dietary fibers as ingredients is a good choice to avoid the discrepancy between desired dietary fiber fortification and consumers acceptability of sensory properties. Beyond this, the right dietary fiber improves sensory properties in many applications such as mouth feel of beverages or freshness of bread. Additionally, new products with attractive properties, e.g. so called breakfast drinks with visible fruit fibers, can be created. An overview about properties and application fields of dietary fibers is given in table 1.

Table 1. Tailored fruit based dietary fibers for food and health industry.

Functional ingredient with physiological and technological aspects

The chemical composition as well as the macromolecular structure determines the properties of commercial dietary fibers. Depending on the type of dietary fiber, physiological effects can be categorized into water holding capacity, gel formation, binding of cations, and binding of sterols and microbiological usability. These physiological effects of dietary fibers can be found in different sections of the gastro intestinal tract (mouth and stomach, small intestine, colon) but also outside of the gastro-intestinal-tract. (Endress and Fischer 2001). Some important effects are listed in table 2. Properties which are equally important from both physiological and technological viewpoints are very interesting ones. An excellent example is the interaction of fruit fibers with water as summarized in table 2.

Table 2. Influence of high water binding fruit fibers.

Generally spoken, soluble fibers are able to immobilize large amounts of water and under certain conditions to form a gel. In contrast insoluble fibers bind less water, but have a more or less fibrous structure that can be helpful to act as non-caloric filler or to enhance the texture in a food system. The sensory perception of insoluble fibers is "rough", but becomes smoother with decreasing particle size or breakage of compact molecule linkages by thermo-mechanical techniques such as done in the case of Heracel AQ Plus fruit fibers.

A certain physiological effect can be obtained by fortification with different dietary fibers. An example is given in figure 1 for the bulking effect. Among other things, bulking is an important parameter to characterize a substance being helpful to prevent constipation and reflects different properties of a dietary fiber such as water binding and ferment ability. On the other hand this shows, that food producers have the possibility to choose among dietary fibers, which fit best to desired texture, viscosity, flavor etc. For example a low viscosity pectin for soft drinks, a classic fruit fibers for bars or cookies and fruit fiber with high water binding like Herbacel AQ for an instant soup.

Fig 1. Faecal Bulking Index (FBI).
FBI (Monro 2000) reflects non-digested food matter, hindgut bacterial biomass
and the water-holding capacity of the whole.
Reference was 12.5% wheat bran (100) to the normal diet (bases = 0).

Tailor-made fruit fibers for individual needs

Today, the natural behavior of fibers can be tailored to fulfill criteria that are ideal for individual needs. Different processing steps such as milling, degradation of molecular mass or washing exist to obtain special properties. Very few, if any of these modifications have been applied to dietary fibers or raw materials and thus a great potential still exists in this area. In case of apple pomace extensive studies led to a number of products:

• Low viscosity pectin (e.g. Herbapekt SF 50-LV)
• Pectin-enriched fruit fiber (e.g. Multipekt Plus 03)
• Classic fruit fiber with defined particle size (e.g. Herbacel Classic AF 01)
• Fruit fiber with improved technological properties (Herbacel AQ Plus Fiber)

The food industry now has dietary fibers that meet the highest demands of the consumers. For almost any application, food technologists can find ideal dietary fibers with versatile functionalities. In addition to the improvement of the dietary profile, DF serves as a good marketing element.

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