Implications of two different methods for analyzing total dietary fiber in foods for food composition databases

• Published in: Journal of food composition and analysis Vol. 84; p. 103253
• Main Authors: Phillips, Katherine M., Haytowitz, David B., Pehrsson, Pamela R.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-12-2019
• Subjects: Analytical methods; Beans; Dietary fiber; Food analysis; Food composition; Food composition databases; Legumes; Nutrition; Potatoes; Quality control; Food composition databases; Analytical methods; Legumes; Beans; Nutrition; Potatoes; Quality control; Food composition; Food analysis; Dietary fiber
• ISSN: 0889-1575; 1096-0481
• DOI: 10.1016/j.jfca.2019.103253

•Dietary fiber (DF) content of different foods analyzed by two methods and compared.•Enzymatic-gravimetric (EG; AOAC991.43) and modified EG (mEG; AOAC2009.01, 2011.25).•mEG greater than EG in uncooked but not cooked dried pulses, popcorn, refried beans.•Innate analytical variability impaired detecting differences > 3 g/100 g in some foods.•More precise methodology, data for DF components, focus on key sources are needed.
Since 1989, total dietary fiber values in USDA databases were determined by the enzymatic-gravimetric (EGF) method (AOAC 991.43), where “fiber” is the residue remaining after samples are subjected to enzymatic treatments mimicking digestion. In 2009 EGF was modified to recover additional non-digestible components (e.g., galacto/fructo-oligosaccharides, polydextrose, resistant starch) (AOAC 2009.01, 2011.25) (mEGF). Limited mEGF data and high cost create a need to identify suitable foods for analysis. USDA’s National Food and Nutrient Analysis Program sampled suitable foods for analysis by EGF and mEGF. No detectable difference between EGF and mEGF was found in almonds, wheat bread, oatmeal cookies, tortilla chips, taco shells, kale, fast food French fries, or cooked dried pulses. mEGF exceeded EGF in uncooked dried pulses (5.4–10.5 g/100 g), raw potatoes (13.7 g/100 g), and cooked plantains (3.1 g/100 g), and slightly higher (0.7–2.2 g/100 g) in hummus, canned refried beans, prepared wild rice mix, and frozen raspberry berries, concentrate, and puree. Statistical power was hindered by high analytical uncertainty, especially for mEGF (up to 33% RSD), likely due to cumulative errors in the multiple steps comprising mEGF. mEGF analyses should focus on foods containing significant levels of fiber components not included in EGF, and reporting individual, particularly metabolically active, fiber components.