Preparation of water-soluble oxidized starch with high carbonyl content by sodium hypochlorite

摘要

Water-soluble oxidized starch with high carbonyl content (DOCo = 0.40) was prepared using a one-step method with sodium hypochlorite (NaClO) as the primary oxidant and under the mediation of sodium bromide (NaBr) and hydroxylamine hydrochloride (NH_2OH.HC1). The influences of pH, initial starch concentration, and the amount of NaBr and NH_2OH.HC1 on the carbonyl and carboxyl content were discussed. The molar ratio of carbonyl to carboxyl groups can be adjusted from 0.8 to 2.2 by controlling the dropping speed of NaClO. The formation of carbonyl and carboxyl groups on the oxidized starch was confirmed by Fourier-transform infrared (FT-IR) and ~(13)C NMR spectroscopy. The molecular weight of the oxidized starch determined by SEC, revealed modest degradation. Besides, a good solubility of the oxidized starch in cold water was also proved based on the study of its solubility and swelling properties.