Comparison of Three Methods and Two Cooking Times in the Determination of Total Dietary Fiber Content of Dried Legumes

Freeze-dried samples of a variety of dried legumes cooked according to package instructions were analyzed for their total dietary fiber using a recently published method (I) which utilizes porcine pancreatic enzymes. The values from the latest study compared those obtained previously using simplified single enzyme method (II) and an AOAC/MES-Tris buffer method 991.43 (III). Total dietary fiber content varied form 17% (g/100 g dry weight) for chickpeas to 30% for kidney beans as determined by methods (I) and (II), and 30 to 58% with the same legumes using method (III). Comparisons were also made using (II) and (III) on the effect of cooking time on the total dietary fiber values for 10 legumes. Greater variations were found in fiber content between cooking times with method (III). Variations between brands of the same legumes were also more pronounced with the AOAC method. This may be accounted for by the day to day variability of the method when used on samples containing high starch.