Analysis of Low Molecular Weight Soluble Dietary Fiber by Prominence-i

Importance of the topic

Low molecular weight soluble dietary fibers (LMWSDF) such as indigestible dextrin and polydextrose play an increasingly important role in food formulation due to their beneficial effects on digestion, lipid metabolism and glycemic control. Accurate quantification of these fibers is essential for nutritional labeling, regulatory compliance and quality assurance in the food industry.

Objectives and overview of the study

This application note describes an enzymatic-HPLC method for measuring LMWSDF in beverage matrices. The goal was to demonstrate a streamlined sample pretreatment and a high-performance liquid chromatography workflow that meets Japanese Food Labeling Standards for dietary fiber analysis.

Methodology and instrumentation

The analytical protocol combines enzymatic digestion, ion-exchange clean-up and refractive index detection on a Prominence-i HPLC system. Key steps include:

• Enzymatic hydrolysis with α-amylase, protease and amyloglucosidase to remove starch and protein.
• pH adjustments and incubation in buffered conditions (pH 6.0, 7.5 and 4.3) at controlled temperatures.
• Ion-exchange column treatment (AMBERLITE™ IRA-67/200CT) to remove residual salts and proteins.
• Analysis on two Shim-pack SPR-Na ligand-exchange columns (250 mm × 7.8 mm, 8 µm) in series, with water as mobile phase at 0.50 mL/min, 80 °C and RID-20A detection.

Key results and discussion

Two beverages containing indigestible dextrin were analyzed. Chromatograms were divided by retention time into mono-, di- and oligosaccharide fractions. Peaks eluting at or before maltotriose defined the LMWSDF fraction. Glucose produced by starch hydrolysis, quantified via a pyranose oxidase assay, served as an internal reference. The HPLC data showed clear separation of LMWSDF from glucose and other mono-/disaccharides in both samples, enabling reliable quantification.

Benefits and practical applications of the method

The combined enzymatic-HPLC approach offers:

• Improved recovery and specificity for low molecular weight fibers vs. traditional gravimetric methods.
• Omission of ethanol precipitation and filtration when only LMWSDF is present, reducing sample preparation time.
• Compatibility with regulatory requirements for nutritional labeling in Japan and other regions.

Future trends and potential applications

Advances in column technology and detector sensitivity may further enhance throughput and lower detection limits. The method can be adapted for complex food matrices, enabling broader screening of functional fibers. Integration with automated sample preparation platforms will support large-scale quality control in the food industry.

Conclusion

The enzymatic-HPLC protocol on the Prominence-i system provides a robust, accurate and efficient means to quantify low molecular weight soluble dietary fibers in beverages. Adoption of this method can improve compliance with labeling standards and support the development of fiber-enriched products.

References

Food Labeling Standards — Appendix: Methods of Analysis of Nutritional Composition. Notification No. 139, Consumer Affairs Agency, Japan, March 30, 2015.