Structural studies of resistant starch derived from processed (autoclaved) rice

Resistant starch (RS), isolated by hydrolysis with Termamyl, protease and amyloglucosidase, of five-cycle autoclaved rice was purified by size exclusion chromatography. Structural characterization by beta-amylolysis, C-13 NMR and methylation followed by GC-MS analysis revealed RS to be a linear (1-->4)-alpha-D-glucan,originating probably from amylose. Its molecular weight was low, 1.20 x 10(6) Da, and amounted to 7400 D-glucose residues. X-ray diffraction measurements showed RS to have both B-type and V-type diffraction patterns. Differential scanning calorimetry data revealed the thermal stability characteristics of RS. The undigested material (equivalent to RS) recovered from the ileum of rat intestine exhibited an almost comparable GPC profile, molecular weight and lambda(max) characteristics with those of in vitro isolated RS.