Abstract:
In the field of nutrition, complex carbohydrates have
become increasingly important in the last decade. The fiber
fraction of foods has been implicated as modifying the
etiology of several chronic diseases and the starch fraction
is important with respect to the glycemic index of foods.
This study has focused on the complex carbohydrate fraction
of three cereal brans: barley, oat, and wheat.
Compositional analyses of each of the brans, untreated and
following simulated processing, were done by adaptations of
the methods of the Association of Analytical Chemists
(1990). Analyses for moisture, fat, ash, protein, starch,
total dietary fiber, and beta-glucans are reported. Oat and
barley brans had similar compositions, but both differed
substantially from the wheat bran preparation as summarized
below. Oat and barley brans had total dietary fiber
contents of approximately 17% and 20% of the dry weight,
respectively. Wheat bran contained approximately twice as
much total dietary fiber (38%). The beta-glucan fraction of
the total dietary fiber was similar for the barley (29%) and
oat (28%) brans, but wheat bran had negligible quantities of
beta-glucans. The starch content of the brans ranged from a
low of 21% for wheat bran to a high of 55% for barley bran.
Simulated in vitro digestion studies using pancreatic enzyme
preparations suggested that the starch fraction of oat and
barley brans is readily broken down within the small
intestine. Greater than 75% of the starch component of oat
bran was solubilized or digested within the first hour of
enzyme exposure. Extended digestion periods reduced the
starch content of the insoluble bran to less than 10% of its
original value. This result suggests that less than 10% of
the starch fraction of oat bran may enter the large
intestine as a substrate for microbial fermentation.
