AOAC RI ERP E-Book - DS DF

OMAMAN-38 B: Collaborative Study Protocol Expert Review Panel Use Only September, 2017

It is essential to ensure that the increased levels of enzyme, especially the AMG, do not lead to hydrolysis of other dietary fiber components such as fructo-oligosaccharides, galacto-oligosaccharides, resistant maltodextrins etc. Studies confirming this were previously reported (6, 7). After incubation with PAA/AMG, the pH of the incubation mixture was increased to ~ 8.2 followed by temporary heating to ~ 100 o C to inactivate the PAA and AMG and promote denaturation of protein, thus providing for efficient protein hydrolysis by protease after cooling the solution to 60 o C. IDF + SDFP was recovered gravimetrically after alcohol precipitation of the SDFP, and combining this result with SDFS determined by HPLC, gives the value for TDF. Reducing the incubation time with PAA/AMG from 16 to 4 h has the advantage of removing the risk of microbial contamination of the sample during the extended incubation. Thus, there is no need to add sodium azide to the incubation buffer. While the dissolution of PAA/AMG in the method employs a buffer containing sodium azide, the presence of sodium azide is not essential and can be omitted if the enzyme is used soon after preparation and is kept on ice before use. However, the use of sodium azide is still recommended in the maltodextrin chromatographic standard solution and the glucose/glycerol reference solutions as these solutions can be prepared and stored for several years before use. In this method, the concentrates containing SDFS from the samples were analysed using TSK gel permeation columns with in-line removal of anions and cations (10). The in-line desalting cartridges obtained from Bio-Rad have a limited capacity, being able to desalt only 25-30 samples before becoming exhausted. To reduce the very significant cost factor (the cartridges are expensive), the concentrates are deionized in a polypropylene tube containing anion and cation exchange resins prior to chromatographic measurement. This results in 90-95% removal of ions and extends the life of the HPLC deionization cartridges by 10 to 20 times as many injections. In the current method, SDFS is analysed on TSK ® gel permeation columns with a glycerol internal standard (6). If a sample being analyzed contains glycerol, diethylene glycol is a suitable internal standard alternative. In AOAC Method 2009.01, a Waters Sugar-Pak ® column is employed with D-sorbitol as the internal standard. However, on AOAC Resear h Institute ERP Use Only

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