Dietary Fibre - ILSI Argentina

Dietary Fibre 19
A variable proportion of dietary fibre will be derived
from isolated or synthetic indigestible carbohydrates,
incorporated into food products, for example, nondigestible
oligosaccharides (fructo-oligosaccharides,
galacto-oligosaccharides), resistant starch, resistant
maltodextrins and polydextrose (Table 7).
TABLE 7
Some synthetic and modified fibres
Fibre component
Fructo-oligosaccharides
Oligofructose
Galacto-oligosaccharides
Gluco-oligosaccharides
Xylo-oligosaccharides
Polydextrose
Resistant maltodextrins
Resistant starches
Production process
Transfructosylation of sucrose with a
ß-fructosidase of Aspergillus niger
Partial enzymatic degradation of
native plant inulin
Enzymatic transgalactosylation of
lactose
Transglycosylation using
dextransucrase from Leuconostoc
mesenteroides
Partial enzymatic hydrolysis of xylan
by xylanase from Trichoderma sp.
Thermal polymerisation of glucose
with sorbitol and acid (as a catalyst)
Alkaline heat treatment of starch
Retrogradation of high amylose starch
ANALYSIS
As noted above, no single analytical method is able to
measure all fibre components in foods. There is a need
for analytical methods that quantify the components in
the dietary fibre definition, and at the same time
excludes other food components. Box 1 and Table 1
describe the principal methods of analysis for dietary
fibre currently in use.
Since 1985, the main accepted official method for
measurement of total fibre has been the enzymaticgravimetric
method of the AOAC (no. 985.29). However,
as the definition of dietary fibre has evolved and a range
of other AOAC and AACC approved methods have been
adopted, total dietary fibre methods do not quantify the
wider range of components now considered as dietary
fibre.
In the UK, for the purposes of food composition tables,
dietary fibre is measured as non-starch polysaccharides
by the Englyst method (Box 1). However, the AOAC
method (985.29) generates significantly higher values for
dietary fibre than the Englyst method, particularly for
foods rich in starch such as potato, bread, beans and
cornflakes. This results from the recovery of some of the
RS3 fraction of resistant starch as dietary fibre. In foods
containing lignin, such as whole grain cereals, the fact
that lignin is not included in the non-starch polysaccharides
analysis contributes further to the lower
values for this method. Therefore it is important to
recognise that where the Englyst values are used in food
tables and as the basis for dietary recommendations, as in
the UK, values will not always coincide with the declared
values on food product labels, which are based on the
enzymatic-gravimetric AOAC method.