Soluble (SDF), insoluble (IDF) and total (TDF) dietary fiber were determined by an enzymatic-gravimetric method according to Lee et al. Duplicate test samples were sequentially treated for starch gelatinization and enzymatic starch and protein digestion in three incubation steps: heat stable alpha-amylase (or termamyl) (1500-3000 units/mg protein; Sigma Chemical Co.) at 95 to 100°C for 15 min; amyloglucosidase (5000-8000 units/ml; Sigma Chemical Co.) at 60°C for 30 min, pH 4.0-4.7; and protease (7-15 units/mg protein; Sigma Chemical Co.), pH 7.5. In this experiment, sample was
suspended in MES/ TRIS buffer. The enzyme digestate was then filtered using acid-washed celite on a Fibertec system E1023 filtration unit (Tecator, Sweden). Following filtration, the remaining residue was the IDF and the filtrate was the SDF. The IDF was washed with two portions of 15 ml 78% ethanol, 15 ml 95% ethanol and 15 ml acetone. For SDF, the filtrate was precipitated with 95% ethanol at 60°C before filtering. The SDF was then washed with two portions of 15 ml 78% ethanol, 15 ml 95% ethanol and 15 ml acetone. TDF, IDF and SDF residue values were all corrected for undigested protein, ash and blank.