2.2.5. Total dietary fibre
(K-TDFR 03/2009, Megazyme).
Total dietary fibre (TDF) was determined using method based
on AOAC Method 985.29 on duplicate samples of dried and defatted
(if fat content is >10%) material. Samples are cooked at 100 C
with heat stable a-amylase to give gelatinisation, hydrolysis and
depolymerisation of starch; incubated at 60 C with protease (to
solubilise and depolymerise proteins) and amyloglucosidase (to
hydrolyse starch fragments to glucose); and treated with four volumes
of ethanol to precipitate soluble fibre and remove depolymerised
protein and glucose (from starch). The residue is
filtered; washed with 78% ethanol, 95% ethanol, and acetone;
dried; and weighed. One duplicate is analysed for protein and
the other is incubated at 525 C to determine ash. The TDF is the
weight of the filtered and dried residue less the weight of the protein
and ash.