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Finding the fibre

   
 
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Choosing a diet high in fibre can give health benefits

A high fibre diet is known to be a healthy choice. The measurement methods to determine fibre levels in food improved a lot in the development of five food reference materials. These materials are useful tools for improving fibre measurements around Europe and they help trade flow moothly within the Single Market.

 

Healthy foods are becoming increasingly popular across Europe. A diet high in fibre is claimed to provide some protection from "Western" diseases. This includes reducing cholesterol in the blood, reducing the risk of intestinal cancer and aiding the heart and bowel functions. With more and more scientific evidence of the benefits of increasing the amount of fibre we eat, consumers are choosing products that are labelled as high fibre content.

If the packaging claims that the food inside is full of dietary fibre, the mass of fibre per 100g of the product must also be stated, according to an EC Directive on Nutrition Labelling of Foodstuffs. This Directive lays out what nutritional information must be labelled on food that is marketed within the European Community.

Packaging claims must be substantiated

Although manufacturers know that they must state the amount of fibre in food, the law does not actually provide a definition for dietary fibre, nor does it specify a method to be used to analyse food for fibre content. There has been an on-going debate throughout Europe about what method should be used to measure fibre.

As each of the three main methods measures a slightly and subtly different substance, it is virtually impossible to compare two packets of breakfast cereal for their nutritional content. Without comparable measurements, food products cannot move freely within the Community.

Disputes arise in these situations and they are time consuming and expensive to resolve. Also, further research into which specific substances in fibre provide health benefits becomes unbelievable if there is no specified method.

It was apparent that food industry, research institutions and food inspection bodies should be following mutually recognised methods to measure the fibre, but this would require much work and expense. It would be impossible to implement a single method of measurement, but this project aimed to provide an alternative solution. The partners produced five food Certified Reference Materials (CRM) with the amount of fibre in each sample being specified for the main current methods of fibre determination. Thus, all laboratories are able to trace their results to a reference point and the measurements are comparable.

Three methods to determine fibre content

There are three main methods used for fibre measurements:
  • The AOAC method uses enzymatic and gravimetric analysis where the food is separated into its constituents and each of these fractions is weighed.
  • The Englyst method uses enzymatic analysis with acid hydrolysis and sugar determination.
  • The Uppsala method also uses enzymatic analysis with acid hydrolysis and sugar determination as well as a gravimetric Klason lignin determination
These complex methods have many steps and it was necessary to carry out studies where each laboratory carried out their own fibre measurements. The group then discussed the results in technical meetings. Many meetings were needed to identify errors and improve procedures which may cause uncertainty in the results. The measurement methods were shown to be repeatable and reproducible.

In all, five CRMs of different foods (apple, carrot, haricot beans, full fat soya flour and bran breakfast cereal) were prepared and their fibre has been accurately determined using the three methods as well as two further common variations of the methods. As a result, laboratories analysing for fibre can compare their results with measurements made using different methods.

The project team had to do many studies on the reference materials which must be stable and must not decompose over time. This is hard to achieve with food materials as chemical and microbiological activity changes the composition of food over time. An example of this is seen when fruit goes mouldy. The solution is to remove the water from the food and package it well in order to preserve it.

All the partners provided knowledge and experience

The two main partners were the coordinator's laboratory, RHM Technology in the UK and a Belgian laboratory at the Ministère des Affaires Economique. Dr Alan Pendlington, the coordinator, explains the rôles of these partners "Apart from coordination, our laboratory prepared and packed the reference materials and carried out the analysis to confirm homogeneity and stability. The Belgian lab carried out analysis for the AOAC method. In addition, between 30 and 40 labs representing 15 European countries were involved in various stages of the project." He goes on to say, "Each participant contributed their wide experience and expertise and this was shared at the meetings which were a vital part of the project. Sharing ideas and experiences made it possible to improve the measurements being made and allowed the materials to be certified."

Since the beginning of 1997, the reference materials have been available through the Institute for Reference Materials and Measurements in Belgium. They are now used all over Europe in the national regulatory laboratories, food manufacturers' laboratories and research institutions. There has been considerable interest from outside Europe, where the fibre dispute continues.

 

 

Project Title:  Dietary Fibre Reference Materials

Programmes: Standards, Measurements and Testing
Contract Reference:  

Cordis DatabaseFor more information on this project,
go to the Cordis Database Record

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