Determination of Insoluble, Soluble, and Total Dietary Fiber in Foods Using a Rapid Integrated Procedure of Enzymatic-Gravimetric-Liquid Chromatography: First Action 2022.01

BACKGROUND: A simple, accurate, and reliable method for the measurement of total dietary fiber (TDF) according to the Codex definition (2009) was developed and successfully validated as AOAC Official Method of Analysis (OMA) 2017.16. Subsequently, OMA 2017.16 was modified to allow separate measurement of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) fractions. OBJECTIVE: To perform a collaborative study to evaluate the repeatability and reproducibility of OMA 2017.16 modification for the measurement of total dietary fiber (TDF) as IDF and SDF measured as (1) water SDF that precipitates in 78% aqueous ethanol (SDFP), and (2) water SDF that remains soluble in 78% aqueous ethanol (SDFS) of degree of polymerization ≥3. METHODS: Duplicate test portions are incubated with pancreatic α-amylase (PAA), amyloglucosidase (AMG), and protease under the conditions employed in OMA 2017.16. For the measurement of IDF, the digestate is filtered and the IDF determined gravimetrically. SDFP in the IDF filtrate is precipitated with alcohol and captured by filtration and determined. SDFS in the SDFP filtrate is recovered and quantitated by LC. The matrixes included cereal products and flours, vegetables, health food snacks, soup, chocolate, and beans. Additional materials were analyzed by collaborators as “practice samples”. RESULTS: With the diethylene glycol internal standard, all multi-laboratotu (MLV) matrixes resulted in repeatability relative standard deviations (RSD(r)) for TDF analyses of <3.60% and RSD(R) ranging from 4.55 to 9.26%. For the practice samples, the RSD(R) for TDF ranged from 6.69 to 11.68%. CONCLUSION: OMA 2022.01 meets the AOAC requirements for repeatability and reproducibility and the data support First Action status. HIGHLIGHTS: OMA 2022.01 is a robust and reproducible method for the analysis of insoluble, soluble (SDFP and SDFS), and TDF in a wide range of matrixes.