Determination of Total Dietary Fiber in Foods, Food Products, and Total Diets: Interlaboratory Study

Abstract

Abstract An interlaboratory study was conducted to determine the total dietary fiber (TDF) content of food, food products, and total diets, using a combination of enzymatic and gravimetric procedures. Thirteen unknown products including 2 mixed diets (one lacto-ovo vegetarian and the other nonvegetarian) were analyzed by 32 analysts. Duplicate samples of dried foods were gelatinized with Termamyl, a heat-stable alphaam) lase, and then enzymatically digested with protease and amyloglucosidase to remove the protein and starch present in the sample. Four volumes of 95% ethanol were added to precipitate the soluble dietary fiber. The total residue was filtered, and then washed with 74% ethanol, 95% ethanol, and acetone. After drying, the residue was weighed. One of the duplicates was analyzed for protein, and the other was ashed at 525°C and the ash was measured. TDF was calculated as the weight of the residue less the weight of protein and ash. Coefficients of variation for 10 of the samples ranged from 2.95 to 26.39%. For 3 of the samples high coefficients of variation were obtained. The results compared satisfactorily with those obtained previously by the best method available for the individual foods studied.