Samples (defatted if necessary) are digested with a mammalian alpha-amylase and an amyloglucosidase for 16 hours at 37oC to simulate the human digestive system. Following digestion, the sample is heated to 95oC to denature all enzymes and proteins present and then digested at 60oC with protease. Insoluble digestion resistant material (dietary fiber) is filtered away and the amount of Insoluble Dietary Fiber (IDF) is determined gravimetrically with protein and ash content subtracted (note: protein and ash are determined on the residue). The dietary fiber remaining in solution following the filtration is precipitated with ethanol and is collected in a second filtration step. The amount of dietary fiber collected in the filter is determined gravimetrically with protein and ash subtracted as above and is recorded as the Gravimetric Soluble Dietary Fiber (G-SDF). The filtrate containing the soluble dietary fiber not precipitated by the ethanol is concentrated and analyzed by High Performance Liquid Chromatography (HPLC) to determine the total HPLC-Soluble Dietary Fiber (HPLC-SDF) with a degree of polymerization (DP) greater than or equal to 3 (DP3). The total Soluble Dietary Fiber is calculated as the sum of the Gravimetric-Soluble Dietary Fiber and the HPLC-Soluble Dietary Fiber (SDF = G-SDF + HPLC-SDF). Total dietary fiber is calculated as the sum of the Insoluble Dietary Fiber and the Soluble Dietary Fiber (TDF = IDF + SDF).
At this time believed to be acceptable for all foods and food products
Stevia can cause interference with the chromatography. Samples containing >2% stevia will damage the instrument therefore cannot be run through this method. Glucomannan
Standard Gravimetric Analytical Chemistry Equipment and HPLC
Please supply expected estimates. Indicate matrix type and indicate if samples are high in fat (>5%). Indicate whether the sample contains fructans (inulin or fructooligosaccharides (FOS)), or psyllium, flax and gum (i.e. guar gum).
Please include notification for samples containing DP2 and DP3 carbohydrates (Isomalto-oligosaccharides (IMO), Maltiltol, Lactose).
Measures dietary fiber including resistant starch and non-digestible oligosaccharides of DP >3. Dietary Fiber is the portion of the carbohydrates which is not digested in the human gut. It is composed of both soluble and insoluble components. These methods are applicable to all food products; however samples containing psyllium or fructans should be submitted under specific test codes. High-fat (>5%) samples require special handling.