ORIGINAL PAPER
Methods for analysis of dietary fibre - advantage
and limitations
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Danish Institute of Animal Sciences, Department of Nutrition,
Research Centre Foulum, P.O. Box 50,
DK-8830 Tjele, Denmark
Publication date: 1997-05-15
J. Anim. Feed Sci. 1997;6(2):185-206
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ABSTRACT
The two main approaches for the determination of dietary fibre (DF) in food and feedstuffs are
the enzymatic- and nonenzymatic-gravimetric AOAC (Association of Official Analytical Chemists)
procedures and the enzymatic-chemical Englyst and Uppsala procedures. The main analytical
problems which have been shown to influence the performance of the enzymatic-gravimetric AOAC
procedures are: variable starch removal, too high final phosphate buffer concentration, and hence
variable ash content of gravimetric residues, problems with residual nitrogen determination,
filtration problems of viscous and desugared fruit samples, and variable blank values. Standardisation and improvements of the methods have gradually improved the performance of the
gravimetric procedures to acceptable levels. The enzymatic-chemical methods with gas-liquid
chromatography (GLC), high performance liquid chromatography (HPLC) or colorimetry as endpoint determination are generally more complex, involve more steps and require, for the GLC and
HPLC methods, more advance equipment than the gravimetric procedures. The efficiency of starch
removal, the hydrolytic conditions for acid hydrolysis of DF polysaccharides, factorial corrections
for hydrolytic losses of sugars and laboratory expertise are identified as factors influencing the
reproducibility of the methods. Modifications and optimisation of the various steps and the build-up
of expertise in laboratories participating in the collaborative trials have improved the reproducibility
of the enzymatic-chemical methods to a level similar to that of the enzymatic-gravimetric AOAC
methods. Technical problems which may introduce errors in the determination of DF with all
methods are incomplete precipitation in 80% (v/v) ethanol, impurities in bacterial amyloglucosidases
resulting in depolymerisation and potential losses of DF polysaccharides. A recent BCR Reference
Material Study indicate that the various DF methods give comparable results for cereal based materials when appropriate corrections are made for lignin and resistant starch. The same was the
case with full fat soya. It is concluded that the techniques for measuring DF are as reproducible as
other analytical methods for feed and food labelling and for research. The choice of analytical
method depends therefore primarily on the purpose of the analytical work.
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