Legume and cereal starches - why differences in digestibility? II. Isolation and characterization of starches from rice (O. sativa) and ragi (finger millet, E. coracana).

Starches were isolated from rice and ragi (finger millet) flours and studied for
their physicochemical and digestibility properties. Both the starches were poorly
birefringent and non-ionic in nature. They exhibited single stage swelling and low
solubility in water and showed -100% (for rice) and -65% (for ragi) solubility
in DMSO after 60 h. Gas liquid chromatography (GLC) analysis of fatty acid
methyl ester (FAME) derivatives of the isolated starch lipid fractions revealed the
predominance of C16:O in rice starch and both C16:O and C18:2 in ragi starch.
The amylose. content of starch isolates ranged between 22 and 30%. The ragi
starch isolates (I/II) exhibited a slightly higher hot paste viscosity (300 BU) than
those of rice starch isolates (~200BU). Their setback viscosity increase was
minimal. In vitro digestibility studies showed rice starch to be more digestible; in
the native state, pancreatic a-amylase digested rice starch I to 40% and ragi
starch I to -56%; whereas in the gelatinized state, glucoamylase digested the
former to -88% and the latter to -70%.