AOAC RI ERP E-Book - DS DF

OMAMAN-38 A: Collaborative Study Manuscript Expert Review Panel Use Only September, 2017

AOAC Official Method 20 17 .xx Total Dietary Fiber in Foods Enzymatic-Gravimetric-High Pressure Liquid Chromatography Method

(Applicable to plant material, foods, and food ingredients).

A. Principle A method is described for the measurement of total dietary fiber as defined by Codex Alimentarius Commission (CAC). The method quantitates high molecular weight dietary fiber (HMWDF), which includes insoluble dietary fiber (IDF) and fiber which precipitates in the presence of 78% ethanol (SDFP); and fiber which is soluble in 78% ethanol (SDFS). Resistant starch (RS) is captured in the IDF fraction ( Figure 2017.xxA ). This method combines the key attributes of AOAC Official Methods of Analysis 991.43, 2001.03, and 2002.02 and is an update of AOAC Method 2009.01. Duplicate test portions are incubated with pancreatic α -amylase and amyloglucosidase (AMG) for 4 hr at 37 o C in sealed 250 mL bottles in a shaking water bath while mixing in orbital motion, or stirring with a magnetic stirrer, during which time non-resistant starch is solubilised and hydrolysed to glucose and maltose by the combined action of the two enzymes. The reaction is terminated by pH adjustment and temporary heating. Protein in the sample is digested with protease. For the measurement of total dietary fiber, ethanol or industrial methylated spirits (IMS) are added and the IDF and SFDP are captured, on a scintered glass crucible, washed with ethanol and acetone, dried and weighed. One of the duplicate residues is analysed for protein, the other for ash. SDFS in the filtrate is concentrated, desalted with resins and quantitating by HPLC. This method differs from AOAC Method 2009.01 in that incubation time with pancreatic α -amylase and amyloglucosidase is reduced from 16 h to 4 h (with higher concentrations of enzymes used) to better simulate human intestinal residence time; improved desalting and HPLC separation of SDFS is incorporated; glycerol is used as the internal standard; and sodium azide is deleted from the incubation buffer. (a) Grinding mill.— Centrifugal, with 12-tooth rotor and 0.5 mm sieve, or similar device. Alternatively, cyclone mill can be used for small test laboratory samples provided they have sufficient air flow or other cooling to avoid overheating samples. AOAC Research Institute ERP Use Only B. Apparatus

Method updated 2008--08-10 This copy printed 22 August 2017

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