Starch Lab Report

1. Preparation of oxidized starch Oxidized starch was prepared according to the method of Forssel et al. (1995) with slight modifications. 50% slurry of starch was prepared by dispersing 50g of starch in 100 ml of distilled water. The pH was adjusted to 9.5 with 2M NaOH. 20 g of NaOCl (in which 4% active chlorine) was added drop-wise to the slurry over a period of 30 min, while maintaining pH range 9.0-9.5, with constant stirring 30±2°C. The reaction proceeded for 10 min after addition of NaOCl. After the reaction, the pH was adjusted to 7 with 1M H₂SO₄ and the oxidized starch was filtered, washed four times with distilled water by using centrifuge and dried in oven at 30±2.0°C for 48h. Dried starch was powdered with morter and pestle and passed through 200 mm sieve and the powdered oxidized starch was kept in a polythene bag.

Determination of carboxyl content Carboxyl content was determined by using the modified procedure of Chattopadhyay et al. (1997). First, 2g (dry basis) of oxidized taro starch was dispersed in 25 ml of 0.5M HCl. The starch slurry was stirred for 30 min followed by filtration through a medium porosity fritted glass funnel (we used bottman filter paper). The residue obtained was washed with 400 ml of distilled water. The starch cake was then quantitatively transferred to a 500 ml glass beaker and the volume was adjusted to 300 ml with distilled water. The starch slurry was then heated with constant stirring in a boiling water