Fiber

Method Description

This method determines total dietary fiber, including insoluble dietary fiber (IDF), soluble dietary fiber (SDF), resistant starch, and non-digestible oligosaccharides (DP ≥ 3), in accordance with the CODEX definition. Samples (defatted if necessary) are enzymatically digested using mammalian α-amylase and amyloglucosidase at 37 °C to simulate human digestion, followed by heat treatment (95 °C) to denature enzymes and proteins, and subsequent protease digestion at 60 °C. Insoluble dietary fiber (IDF) is isolated by filtration and quantified gravimetrically, with corrections for protein and ash. The filtrate is treated with ethanol to precipitate soluble dietary fiber, which is collected, filtered, and quantified gravimetrically as gravimetric soluble dietary fiber (G-SDF), also corrected for protein and ash. The remaining soluble fraction (non-precipitated) is concentrated and analyzed by high-performance liquid chromatography (HPLC) to determine HPLC-soluble dietary fiber (HPLC-SDF; DP ≥ 3). Total dietary fiber is calculated as the sum of IDF, G-SDF, and HPLC-SDF. Samples containing significant levels of DP2 or DP3 carbohydrates (e.g., isomalto-oligosaccharides, maltitol, lactose) should be identified at submission. This method is applicable to most food products; however, samples containing psyllium or fructans should be submitted under specific test codes. High-fat (>5%) samples require special handling.