AOAC RI ERP E-Book - DS DF

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

levels were increased 2-fold and AMG was increased 12-fold and under these conditions, the resistant maltodextrins formed from non-resistant starch under incubation conditions of AOAC Method 2009.01 were no longer produced. Higher molecular weight dietary fiber (HMWDF) [(IDF + SDFP (soluble fiber which precipitates in the presence of 78% aqueous ethanol)] values obtained for samples not containing resistant starch were essentially the same as those obtained with AOAC Method 985.29 and 991.43. The IDF + SDFP values for many samples containing resistant starch (RS), were very similar to those obtained with AOAC Method 2009.01. Samples containing RS 2 (native, high amylose maize starch) and RS 4 (phosphate cross- liked native starches) however, resulted in much higher dietary fiber values. The current method employing TSK-Gel G2500PWXL ® columns for gel permeation chromatography, gives higher dietary fiber values for fructo-oligosaccharides than were obtained in previous methods using the Waters Sugar-Pak ® column because with the Sugar-Pak ® column co-elutes inulinotriose with disaccharides and thus, does not include inulinotriose in the dietary fiber calculations. Glycerol replaces D-sorbitol as the internal standard in-line with AOAC Method 2001.03 as the D-sorbitol is not separated from D-glucose on the TSK columns. An improved method for preparing samples for HPLC involves removing the bulk of the anions and cations (salt) in the sample by adding the sample to cation and anion exchange resins in a polypropylene tube and mixing thoroughly before the gel permeation separation. This step removes ~ 95% of the cations and anions in the sample, allowing more efficient use of expensive desalting pre-columns in simultaneous in-line deionisation and chromatography. With the shorter PAA/AMG incubation time, it is possible to eliminate the use of sodium azide in the incubation buffer solutions. The method described here measures IDF + SDFP gravimetrically and SDFS by HPLC and the values are combined to give TDF. The method was evaluated through an ICC / AACC International collaborative study. A total of 13 laboratories participated, with all laboratories returning valid assay data for most of the 16 test portions (8 blind duplicates) consisting of samples with a range of content of traditional dietary fibers, resistant starch and non-digestible oligosaccharides. In total, only 4 sets of data from the 104 sets submitted were statistically excluded as outliers. The dietary fiber content of the 8 test pairs ranged from 6.79 to 60.6%. TDF was calculated as the sum of HMWDF (IDF + SDFP) and SDFS. For TDF, the within laboratory variability (s r ) ranged from 0.29 to 0.74 and the between laboratory variability (s R ) ranged from 0.57 to 4.67. The within laboratory AOAC Research Institute ERP Use Only

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