Dietary fibre has become a major public interest because of its claimed protective effects against 'Western' diseases. The Directive on Nutrition Labelling of Foodstuffs issued by the European Economic Community requires quantitative information on the level of dietary fibre in foodstuffs marketed throughout the community. It is extremely important that reliable methods for dietary fibre analysis are used in the member states. Several methods are in use. The methods measure different components and give different results. It is essential that Certified Reference Materials (CRMs) are available for each method. At the start of this project only CRMs for the AOAC 1990 method were available. A major reason for the lack of CRMs by other methods was that the methods were not sufficiently reliable to give certifiable results.
The overall objective of the project was to produce 5 reference materials each certified by 5 different methods of analysis using the latest BCR certification protocol. Particular objectives were:
a) to develop a reliable procedure for each analytical method and demonstrate its repeatability and reproducibility by means of intercomparison studies involving most member states and some non-member European states.
b) to prepare and pack 5 new dried reference materials, haricot beans, carrot, apple, full fat soya flour and bran breakfast cereal and demonstrate their homogeneity and their stability under a range of storage conditions.
c) to carry out certification analyses on all five materials by all five methods, using laboratories which performed well in the intercomparison study.
d) to investigate the composition of the intermediate residues produced during dietary fibre analysis.
e) prepare a report for submission to the Scientific Evaluation Group.
All the objectives were achieved. As a result five new dried dietary fibre reference materials have been certified: haricot beans (CRM 514), carrot (CRM 515), apple (CRM 516), full fat soya flour (CRM 517) and bran breakfast cereal (CRM 518). They are accompanied by a report which gives certified values by five different methods. The methods are (1) the AOAC enzymatic-gravimetric method, Prosky 1990 985.29 and (2) a derivative of this method, Lee 1992 991.43 (3) the Englyst enzymatic-gas chromatographic method and (4) a derivative of this method with a colorimetric end point, (5) the Uppsala method. These methods are fully described in the report. The new CRMs were released for sale early in 1997. To date, nine samples have been sold.
It is anticipated that the availability of reliable comparative dietary fibre values obtained by different methods will be valuable background information for discussions about the definition of dietary fibre and the recommendation of methods for its analysis
The co-ordinators laboratory prepared and packed the reference materials and together with the main partner carried out the analyses to demonstrate homogeneity and stability. Up to 32 laboratories from 15 European countries participated in the intercomparison and certification studies and took part in meetings to develop the methods and review results.