Physicochemical properties, in-vitro digestibility and structural elucidation of RS4 from rice starch.

Starches extracted from four different rice cultivars were phosphorylated by using STMP/STPP to make modified food starches with high contents of type 4 resistant starch (RS4). The results revealed 10- fold improvement in RS4 content by the phosphorylation of starch. The phosphorus % and DS values of rice starches ranged from 0.33 to 0.35, and 0.016 to 0.018, respectively. FT-IR spectroscopy showed reduction of OH stretching band at 3290cm-1 and the appearance of PO at 1244-1266cm-1 which confirms crosslinking of starch with STMP/STPP. Phosphorylation was found to increase water absorption capacity, oil absorption capacity, bile-acid binding and lightness, whereas amylose content, swelling power, solubility index and light transmittance were decreased with phosphorylation. DSC analyses revealed increase in thermal transition temperatures of the crosslinked starches which suggests that the application of STMP/STPP as a crosslinker can improve the integrality and stability of starch. SEM micro-graphs revealed that phosphorylated rice starch granules retained their integrity, while some fissures appeared on the surface of some granules. XRD analysis revealed decreased crystallinity of RS4 rice starches.

Effect of γ-irradiation on structure and nutraceutical potential of ß-D-glucan from barley (Hordeum vulgare).

This paper reports the characterization and potential antioxidant activity of ß-D-glucan isolated from barley treated with γ-rays. The ß-D-glucan was irradiated with 0, 2, 4 and 8 kGy by gamma ray. The samples were characterized by Fourier transform-infrared spectroscopy, gel permeation chromatography (GPC) and quantitative estimation by Megazyme ß-D-glucan assay kit. The average molecular weight of non-irradiated ß-D-glucan was 177 kDa that decreased to 79 kDa at 8 kGy. Antioxidant activity was evaluated by five complementary assays including DPPH, lipid peroxidation, reducing power, metal chelating ability and oxidative DNA damage assays. Further, the antiproliferative potential of irradiated ß-D-glucan was tested against three human cancer cell lines including Colo-205, T47D and MCF7 using MTT assay. Irradiated ß-D-glucan exhibited dose dependent cancer cell growth inhibition. In conclusion, the present study demonstrates that irradiation leads to the formation of low molecular weight ß-D-glucan with enhanced antioxidant and antiproliferative activities.