Bora Rice Starch Analysis

Bora rice (Oryza sativa var.glutinosa)was used for this study, purchased from the local market of Tezpur, Assam, India. Sodium Hydroxide, Potassium Hydroxide, Sodium Potassium Tartrate,1-butanol-hydrochloric acid and Copper Sulphate from Sigma Aldrich were used for the extraction of the starch.

2.2. Starch extraction

The starch from glutinous rice was extracted by alkali extraction method. Rice sample (1kg) was steeped in sodium hydroxide solution (0.3%) at 25°C for 24 hrs to soften the endosperm. The supernatant liquid was drained off and rice samples were grounded. The grounded rice was again dispersed in sodium hydroxide solution (0.3%) and then allowed to settle for 6h. This process was repeated until the supernatant showed negative response to the protein test. Then the separated sediment was suspended in distilled water; the pH of the slurry was adjusted to 7.0 with hydrochloric acid (0.5M) and passed through muslin cloth followed by sedimentation for 6h. The sediment was centrifuged at 5000 g for 15 min and dried at 48 °C for 72 h [8].

2.3. Modification of starch

The 1-butanol-hydrochloric acid modification of glutinous rice starch was carried out according to the procedure described by Hu et al. [9]

For analysis,10% (w/v) dispersions of starch samples were used on the plate and excess sample was removed carefully by using a sharp razor blade. A thin layer of silicon oil was used on the exposed surface of the sample to prevent drying during testing. Frequency sweep tests (mechanical spectra) from 1 to 100 W/s were performed at 30°C. The storage modulus (G′), loss modulus (G″), complex viscosity (η*) and dynamic viscosity (η’) were calculated for each starch samples. The data were analysed using Rheoplus Version 3.61