Physicochemical properties and starch digestibility of Scirpus grossus flour and starch

Flour and starch isolated from the tubers of Scirpus grossus were investigated for their physicochemical properties and starch digestibility. The flour was extracted using two different processes namely peeled and unpeeled processes. Proximate analysis revealed that the flours from both processes contain considerably high total starch, more than 80%, which indicate their potential use as starchy foods. The amylose content of the flours and starches ranged from 29 to 32%. Starch granules of S. grossus were oval in shape with smooth surface and small diameters ranging from 6 to 15 μm. All samples exhibited high swelling pasting behaviors with pasting temperatures ranging from 78 to 79 °C, indicating the strong bonding forces within the granule interiors. Differential scanning calorimetry (DSC) results suggested that the samples gelatinized at temperatures ranging from 71 to 81 °C. In vitro starch digestion assay found that all samples provided the estimated glycaemic index (GI) values of approximately 55 or less.