Resistant starch derived from processed ragi (finger millet, Eleusine coracana) flour: structural characterization

From five cycle autoclaved finger millet (ragi, Eleusine coracana) flour, resistant starch (RS) was isolated by sequential enzymatic digestion and purified by GPC and SE–HPLC methods. Its molecular weight was ∼1.4×106 Da. Permethylation followed by GC–MS analysis revealed the RS to be a linear α-1,4-d-glucan, probably derived from a retrograded amylose fraction of ragi starch. X-ray diffraction data showed the ragi RS to have both B and V-type diffraction patterns. The enthalpy value of ∼0.7 mcal mg−1 showed ragi RS to be thermally stable. The undigested material recovered from the ileum of rat intestine fed with processed ragi flour exhibited a close similarity in some of its properties to that of RS isolated by an in vitro method.