The procedure for the determination of TDF is a slight
modification of the enzymatic-gravimetric method of
Prosky et al. (1985). The finely ground samples were
gelatinized in the presence of heat stable a-amylase
(Sigma Product No. A-5426) and then enzymatically
digested with protease (Sigma Product No. P-3910) and
amyloglucosidase (Sigma Product No. A-9913) to
remove the protein and starch present in the sample. The
water-insoluble dietary fiber (IDF) was filtered and
washed with water and acetone. The filtrate, containing
the soluble dietary fiber (SDF), was retained. The SDF
was precipitated with four volumes of 95% ethanol, filtered
and washed with ethanol. After drying, the IDF
was weighed. Half of the samples were analyzed for
protein and the others were ashed. Correction was
made for protein and mineral content of the residue.
The TDF was the combined soluble and insoluble fiber.