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AACC International Approved Methods - AACC Method 32-25.01. Total Dietary Fiber-Determined as Neutral Sugar Residues, Uronic Acid Residues, and Klason Lignin (Uppsala Method)

AACC International Approved Methods

Fiber

AACCI Method 32-25.01
Total Dietary Fiber-Determined as Neutral Sugar Residues, Uronic Acid Residues, and Klason Lignin (Uppsala Method)

VIEW METHOD

Objective
The principle of the method is illustrated in Fig. 1. The method includes selective and enzymatic removal of starch, using a thermostable alpha-amylase and an amyloglucosidase; precipitation of soluble polysaccharides with 80% ethanol; hydrolysis of amylase-resistant polysaccharides (precipitated and insoluble) with sulfuric acid; and subsequent quantification by gas-liquid chromatography (GLC) of released neutral sugars as alditol acetates. Uronic acids in acid hydrolysate are determined by colorimetry, and Klason lignin (sulfuric acid lignin) is calculated gravimetrically as acid-insoluble residue after correction for ash. The method determines total dietary fiber as the sum of the neutral sugar residues, uronic acid residues, and Klason lignin in food raw material and products. This method is applicable to cereal and vegetable products.