Determination of Total Dietary Fiber (CODEX Definition) by Enzymatic-Gravimetric Method and Liquid Chromatography: Collaborative Study

Abstract

A method for the determination of total dietary fiber (TDF), as defined by the CODEX Alimentarius, was validated in foods. Based upon the principles of AOAC Official MethodsSM 985.29, 991.43, 2001.03, and 2002.02, the method quantitates high- and low-molecular-weight dietary fiber (HMWDF and LMWDF, respectively). In 2007, McCleary described a method of extended enzymatic digestion at 37C to simulate human intestinal digestion followed by gravimetric isolation and quantitation of HMWDF and the use of LC to quantitate low-molecular-weight soluble dietary fiber (LMWSDF). The method thus quantitates the complete range of dietary fiber components from resistant starch (by utilizing the digestion conditions of AOAC Method 2002.02) to digestion resistant oligosaccharides (by incorporating the deionization and LC procedures of AOAC Method 2001.03). The method was evaluated through an AOAC collaborative study. Eighteen laboratories participated with 16 laboratories returning valid assay data for 16 test portions (eight blind duplicates) consisting of samples with a range of traditional dietary fiber, resistant starch, and nondigestible oligosaccharides. The dietary fiber content of the eight test pairs ranged from 11.57 to 47.83. Digestion of samples under the conditions of AOAC Method 2002.02 followed by the isolation and gravimetric procedures of AOAC Methods 985.29 and 991.43 results in quantitation of HMWDF. The filtrate from the quantitation of HMWDF is concentrated, deionized, concentrated again, and analyzed by LC to determine the LMWSDF, i.e., all nondigestible oligosaccharides of degree of polymerization 3. TDF is calculated as the sum of HMWDF and LMWSDF. Repeatability standard deviations (sr) ranged from 0.41 to 1.43, and reproducibility standard deviations (sR) ranged from 1.18 to 5.44. These results are comparable to other official dietary fiber methods, and the method is recommended for adoption as Official First Action.

Modification and Application of Dietary Fiber in Foods

“…For instance, McCleary et al used the Enzymatic-Gravimetric Method to determine high-molecular-weight dietary fiber (HMWDF), using Liquid Chromatography for low-molecular-weight dietary fiber (LMWDF). These methods provide results that are comparable to other official dietary fiber methods, and this method is recommended for adoption as Official First Action [26]. Chemical analysis is generally used to determine the components of dietary fiber, and is often combined with enzymatic methods by using enzymatic treatment to remove the starch and using anhydrous ethanol for precipitation to obtain total dietary fiber.…”

Gastrointestinal Release of β‐Glucan and Pectin Using an In Vitro Method

“…None of these methods are comparable to the solubilization of fibers in the gastrointestinal tract. Several authors (Beer et al 1997;Monro 1991Monro , 1993Monro , 2000 have questioned the use of these methods for different types of fibers due to their limited relevance to gut-soluble fibers, and a new method for the assay of integrated total dietary fiber is applying a protocol more consistent with the human digestive system (McCleary et al 2010). One study by Lazaridou et al (2004) obtained good results by water extraction of βglucan from oat flour at 47°C for 3 hr.…”

Genetic variation in the extract viscosity of rye (Secale cereale L.) bread made from endosperm and wholemeal flour: impact of high-molecular-weight arabinoxylan, starch and protein

“…The contents of extractable, unextractable and total dietary fibre, often referred to in the literature as soluble, insoluble and total dietary fibre (SDF, IDF and TDF respectively), were determined as HMW components according to the enzymatic/gravimetric procedure described by McCleary et al 25 The results obtained by this method were corrected for ash but not for non‐digestible protein.…”