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United States Department of Agriculture

Agricultural Research Service

Title: Comparison of Three Methods and Cooking Time in the Determination of Total Dietary Fiber Content of Dried Legumes

item Li, Betty

Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 17, 1995
Publication Date: N/A

Interpretive Summary: Legumes are important and rich sources of dietary fiber. Previously, we analyzed a variety of legumes, both canned and dried products. In comparing two gravimetric methods, we found that the dried/cooked samples had very different values for total dietary fiber (TDF) depending on the method. In the latest study, we tested a recently published method for TDF on some of the same samples we used before. The results indicated that the new method and our simplified method are comparable while AOAC method 991.43 tends to give much higher values. This information will be very useful to all who use the AOAC method, keeping in mind the likelihood of over-estimating the TDF value because of the presence of residual starch.

Technical Abstract: 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 are compared with those previously using a simplified method (II) and an AOAC/MES-Tris buffer method 991.43 (III). Total dietary fiber content varied from 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 method (II) and (III) on the effect of cooking time on the total dietary fiber values for 10 legumes. Greater variations were found 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.

Last Modified: 4/21/2015
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