Determination of dietary fibre as non-starch polysaccharides with gas–liquid chromatographic, high-performance liquid chromatographic or spectrophotometric measurement of constituent sugars

TLDR

NSP compose approximately 90 % of plant cell‑wall material, making them a useful index of this material. The study describes methods for measuring dietary fibre as non‑starch polysaccharides (NSP). The methods involve enzymatic starch removal, acid hydrolysis of NSP to sugars, and measurement of the released sugars by gas‑liquid chromatography, HPLC, or spectrophotometry, enabling determination of total, soluble, and insoluble NSP. The three analytical approaches give comparable results across diverse foods, and the refined spectrophotometric method is robust enough for food labeling and quality control, while NSP values serve as a reliable marker of a diet rich in fruit, vegetables, and high‑extraction cereals.

Abstract

Methods for the measurement of dietary fibre as non-starch polysaccharides (NSP) are described. A common enzymic removal of starch and acid hydrolysis of the NSP to their constituent sugars are followed by one of three alternative techniques, gas–liquid chromatography, high-performance liquid chromatography or spectrophotometry, for measurement of the released sugars. The results obtained by the three methods are in good agreement for a wide range of raw and processed foods. NSP compose approximately 90% of the plant cell-wall material and are therefore a good index of this material. Values for NSP therefore provide a good marker for a diet rich in fruit, vegetables and high-extraction cereal products associated with health and recommended in dietary guidelines. Values for total, soluble and insoluble NSP may be obtained with any of the end-point techniques, and the detailed information obtained from the chromatographic methods is useful in studies of the relationship between the intakes of various types of NSP and health. The causes of some potential interferences in the spectrophotometric assay, especially from processed foods, have been identified and eliminated. The rapid spectrophotometric version is suitable for food labelling purposes and for quality control, and the changes described have made it more robust.