The Rapid Integrated Total Dietary Fiber Assay Kit method is validated under collaborative study (AOAC Method 2017.16, ICC Standard No. 185) and suitable for the measurement and analysis of Total Dietary Fiber as per Codex Alimentarius definition. This method is updated to be more consistent with in vivo conditions in the human small intestine, i.e. a 4 h incubation time. Under these conditions more accurate measurement of resistant starch is obtained, including phosphate cross-liked starch (RS4). Use of higher enzyme concentrations ensures that resistant maltodextrins produced from non-resistant starch under the incubation conditions of the Integrated Total Dietary Fiber procedure (AOAC Methods 2009.01 and 2011.25) are no longer produced.

In this improved, rapid method, the incubation time with PAA + AMG is reduced to 4 h and the levels of both PAA and AMG are increased to ensure that resistant starch levels obtained with a set of control samples are consistent with ileostomy data. Under these conditions, the DF values obtained for most samples are the same as those obtained with AOAC Methods 2009.01 and 2011.25.

The dietary fiber fractions that are measured with this method are:

1. High Molecular Weight Dietary Fiber (HMWDF) including Insoluble Dietary Fiber (IDF) and High Molecular Weight Soluble Dietary Fiber (SDFP; soluble dietary fiber which is precipitated in the presence of 78% aqueous ethanol), and

2. Low Molecular Weight Soluble Dietary Fiber (SDFS; water soluble dietary fiber that is soluble in the presence of 78% aqueous ethanol).

Alternatively, IDF, SDFP and SDFS can be measured separately.

The enzymes used in this method are high purity and effectively devoid of contaminating enzymes active on other dietary fiber components such as
β-glucan, pectin and arabinoxylan. They are supplied as freeze-dried powders; allowing the use of glycerol as an internal standard in the method.

* See McCleary, B. V., Sloane, N & Draga, A. (2015). Determination of total dietary fibre and available carbohydrates: a rapid integrated procedure that simulates in vivo digestion. Starch/Starke, 66, 1-24.