Summer 2001 Issue — Fruit and Vegetable Extracts with Secondary Plant Substances
The development of an innovative functional food concept

Elke Stich, Dr. rer. Nat.

GNT GmbH, Aachen

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Good health depends on proper nutrition

One of the most important choices you can make to maintain a healthy lifestyle is choosing a nutrient-dense diet. Scientific evidence clearly supports the fact that a proper diet may in fact help reduce the risk for cardiovascular disease and improve immune function later in life.

Fruit and vegetables are among the most important components of a healthy diet. On a mission to increase consumption of fruits and vegetables health organisations and companies in the USA and Canada launched a campaign with the message of eating at least 5 daily servings of fruits and vegetables for better health. Whereas the saying used to be "An apple a day keeps the doctor away", it is "5 A Day" now. A similar campaign was launched in Germany in the summer of 2000 with the slogan "5 am tag" (Fig. 1).

Fig. 1. Secondary plant substances cannot be produced by the human body and therefore must be obtained by eating fruit and vegetables (See Fig. 2).

Secondary plant substances (SPS)

Until recently the potential health benefit of fruit and vegetables was primarily attributed to vitamins and minerals. Research indicates, however, that the benefits are also due to their significant content of "Secondary Plant Substances" (SPS) or bioactive substances.

Secondary plant substances are micronutrients generated in plants as pest and disease repellents and as protection against excessive sunlight. Scientific understanding of their role in the prevention and treatment of specific human diseases is growing quickly. Prevention of cancer, anti-inflammatory and antiviral effects, decreasing cholesterol levels and blood pressure regulation are increasingly correlated to the intake of secondary plant substances. Specific types of fruits and vegetables are credited with a variety of health benefits.

Fig. 2. The most important secondary plant substances, where they are found, and their effects.

Plant extracts with a high SPS content

These scientific findings lead to the recommendation: Eat fruit and vegetables five times a day! A well-filled basket of fruit is, however, not always within reach. This was the reasoning behind producing plant extracts with high-standardized contents of secondary plant substances (SPS).

Selected raw materials

The quality of many processed foods depends on the quality of the raw materials used. Therefore only edible fruits and vegetables with a high SPS content should be considered for the production of extracts. The plants to be processed are first selected on the basis of literature searches. The range of suitable varieties is then further narrowed down by screening the varieties and by initial field tests. Seeds or seedlings must then be obtained for production in the quantities needed for industrial processing. Many years of hard work lie between the idea for a product and its introduction into the market.

Fully ripened fruit or vegetables offer not only the ultimate in taste and flavour but also maximum colour intensity and hence the highest content of secondary plant substances. The amount of the desired SPS is continuously monitored during the ripening process, ensuring that only ripe fruit and vegetables with a high SPS content are harvested. These fruits and vegetables have a considerable advantage over those sold in supermarkets, which has been harvested, unripe and therefore have a lower SPS content.

Careful processing - as close to nature as possible

Right after harvesting, the fruits and vegetables are frozen on-site or processed. This avoids the loss of SPS that would result from lengthy storage. The processing methods are developed specifically for each fruit and vegetable and tailored to the SPS in question. Carrots, for example, in which the non-water-soluble carotenoids are among the valuable SPS, are processed quite differently from blackcurrants, which contain many water-soluble anthocyanins.

During processing the SPS are not extracted selectively from the fruit or vegetable; instead, an aqueous full extract is first produced. Water, simple sugars and acids are partially removed from this extract. All the valuable ingredients typical of the fresh fruit and vegetable are preserved in the extract as far as possible, including flavonoids, carotenoids, complex carbohydrates, vitamins, minerals, amino acids and trace elements.

The manufacturing process operates continuously and not on a batch-to batch basis, reducing residence time to a minimum. Only physical techniques are used, such as washing, chopping, pressing, filtering, separating, concentrating and pasteurising, and only water is used as the extracting agent.

Bioactive substances are sensitive to high temperatures, so processing has to be carried out at the lowest possible temperatures. Using membrane separation methods that run at their best at low temperatures can successfully do this.

The final concentration and pasteurisation is also done in a very gentle manner with extremely short residence times. Immediately after production, the finished product is cooled and stored at - 18°C (Fig. 3).

Fig. 3

Nutrifood® - a functional food

The result of these production processes - Nutrifood® products - are sold worldwide by the GNT Group. They mostly are extremely colour-intensive viscous concentrates with a high content of secondary plant substances.

These extracts are functional foods that can be enjoyed without diluting since they taste delicious. An example is Nutrifood® Complex, a concentrate of ten different fruits and vegetables. Just 5ml of this Nutrifood® contains as many secondary plant substances as 250g of ordinary fruits and vegetables; a teaspoonful - almost equivalent to the contents of a small fruit basket! These extracts are also delicious in yoghurt, Muesli, ice cream, quark, and fruit juices.

Nutrifood® makes the latest scientific expertise about secondary plant substances available.

Nutrifood® as an ingredient in other functional foods

Nutrifood® can also be incorporated into a variety of products for the promotion of health and well being. Various mixtures can meet the requirements of almost every customer. The best uses are in confectionary, fruit preparations and yoghurts, as well as in milk, cottage cheese, and of course drinks (Fig. 4).

Fig. 4. Products to which Nutrifood® has been added meet the need of the consumer for health nutrition while providing additional sensory enjoyment.

Standardized SPS values

For more convenience in industrial production our products are standardized with regard to the content of secondary plant substances. We also make sure that the visual effect remains unchanged: with colourfulness in mind we standardize to those SPS, which are responsible for colour strength (carotenoids and anthocyanins). SPS and colour are closely related: the fruit's colour intensity signals the degree of ripeness and thus also the achieved SPS content. The strongly colouring carotenoids and anthocyanins are also among the most important group of SPS and have a particularly high antioxidant capacity.

Test methods

The antioxidant capacity of a fruit or vegetable concentrate is a very interesting parameter. Various in vitro test systems are available, such as for example the TEAC (Trolox Equivalent Antioxidant Capacity) test. All the tests indicate the antioxidant potential of this food group, but the results cannot be compared with each other. The absolute values may vary considerably from one laboratory to another depending on the test method. So far reliable test methods are only available for water-soluble SPS such as anthocyanins and polyphenols. As far as we know the antioxidant potential of carotenoids cannot be measured reproductively yet.

Food, not additives

Fruit and vegetable extracts produced according to the above-mentioned principles are foods and not additives, since neither chemical synthesis nor selective extraction of SPS with organic solvents has been carried out. This is an important fact for industrial users. Take the well-known carotenoid lycopene as an example: the product produced by the method described here is not selectively extracted lycopene from tomatoes, but a concentrated tomato produced with a very high content of lycopene.

Therefore, within the EU, Nutrifood® can be labelled "fruit and vegetable extract" in the list of ingredients.

Pleasant taste

Nutrifood® has a delicious and aromatic taste, which is characteristic of the processed raw materials. A high content of SPS permits a low dosage in the final product, ensuring overall flavour rather than the domination of one specific flavour. Both sweet and salty ranges are available. Other flavours can be added simultaneously that correspond to the colour of the finished product but do not necessarily originate from the same source. For example, an extract obtained from pumpkin can be combined with oranges or orange flavour.

Marketing statements for functional foods with Nutrifood®

So far health claims on SPS are not permitted in the EU and official recommendation for consumption do not yet exist (except for ß- carotene which has a reference value of 2-4 mg/day). Nonetheless marketing statements can be made that will draw the attention of health-conscious consumers. The processed fruit and vegetables can be referred to with a statement such as "contains the bio-active substances of 100g of tomatoes (calculated on the basis of the lycopene content)" or "contains the bio-active substances of 100g of red berries (calculated on the basis of the anthocyanins content)".

Summary

Consumer behaviour shows a clear trend towards more nutrition awareness, but very few people consume the recommended five portions of fruit and vegetables a day.

It is to be expected that foods, which meet the daily requirements, will be increasingly enriched with fruit and vegetable extracts with a uniformly high standard of SPS. In this way consumers can eat more healthily without changing their buying, cooking, or eating habits, and need not forego enjoyment of their food.

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