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Interlaboratory evaluation of AACC Method 32-45.01 for the measurement of total dietary fiber
B. MCCLEARY (1), A. Draga (1), J. Cox (1) (1) Megazyme International Ireland, Bray, Ireland.

AACC Method 32-45.01 (AOAC Method 2009.01; Codex Type I method) has been updated to allow for deficiencies identified in the method when it was employed across a diverse range of food materials. These limitations included; the fact that the incubation time with pancreatic a-amylase (PAA)/and amyloglucosidase (AMG) is 16 h whereas the likely time of residence of food in the small intestine is 3-5h; phosphate cross-linked starches (RS4) are underestimated; resistant maltodextrins are produced from non-resistant starch under the incubation conditions used in 32-45.01; fructo-oligosaccharides are underestimated using Sugar-Pak columns (F3 elutes after sucrose); sodium azide preservative is essential with incubation times of 16 h, but is undesirable; sample deionisation for HPLC is tedious; D-sorbitol is not considered to be the best internal standard. In the updated method, the incubation time with PAA/AMG was reduced to 4 h and levels of PAA (5 KCU/assay) and AMG (1.7 KU/assay) were increased. A simplified procedure for deionization of samples was developed and glycerol was introduced as internal standard. HPLC was performed on TOSOH TSK-GELR G2500PWXL gel permeation columns with in-line desalting. This method is currently under evaluation and results will be presented in this paper.