Challenges and Constraints in Analysis of Oligosaccharides and other Fibre Components

Dietary fibres are plant components that resist digestion and that have physiological effects on human and animal health. Establishing a comprehensive definition of dietary fibre has been both controversial and challenging. The most internationally accepted definitions are those given by AACC International and the Codex Alimentarius Commission, which define dietary fibre based on both carbohydrate composition and physiological effects.

The evolving definition of dietary fibre has interacted with advances in the ability to quantify and characterise its diverse components. The earliest method for carbohydrate quantification in food and feed was by difference after measuring the more tractable components (water, protein, lipids and ash). Later methods employed gravimetric estimation of fibres after removal of digestible components of the sample. However gravimetric methods are incapable of characterising the structure of fibres or of measuring the small oligosaccharides, which have become of increasing interest for both human and animal nutrition due to their potential prebiotic benefits. A range of instrumental methods have therefore been applied to understand dietary fibre components more fully, including nuclear magnetic resonance spectroscopy (NMR) and chromatography.

Measuring total dietary fibre by chromatographic methods requires hydrolysis of polysaccharides into constituent monosaccharides. Acid hydrolysis is the usual method, but the kinetics of hydrolysis are affected by the nature of the carbohydrates and the sample matrix, such that optimising hydrolysis conditions for different samples remains challenging.

High performance anion exchange chromatography with pulsed amperometric detector (HPAEC-PAD) has emerged as the method of choice for polysaccharide quantification (via hydrolysis to monomers) and for oligosaccharide analysis. The ability to measure oligosaccharides has been driven by their increasing prebiotic importance and empowered by the availability of standards and new chromatographic methods, such that the understanding of how to produce and exploit these molecules is beginning to accelerate.

Presented at the International Fibre Summit 2019 (https://internationalfibre.com/). Reproduced with permission from the organizers.