Microwave-Assisted Synthesis Of Phosphorylated Corn Starch

Abstract

Phosphorylated starch is one of modified starches which is commonly imported. In general, starch resource to be modified must have more than 25% amylose. This study aimed to synthese phosphorylated starch and evaluate its potency as adosrbent. Corn starch was subjected to phosphorylation through microwave-assisted reaction of starch with a mixture of sodium dihydrogen orthophosphate and disodium hydrogen phosphate. The experiment was designed tooptimizeparameter of pH, microwave power irradiation, and microwave irradiation time. The results showed that the maximumphosphate substitution degree was obtained at a pH of 6, microwave irradiation of 500 W, and a reaction time of 10 minutes. The degree of subtitution ranged from 0.567 to 0.787. The physicochemical properties of the product as swelling capacity, solubility, water binding capacity, and paste clarity were significantly different than that of the unmodified corn starch. The infrared spectrum showed a high peak absorption in the wavenumber of 1651 cm-1, indicating hydrogen bonding formation phosphoric group-water- phosphoric group. In the fingerprint area, there were two new absorption peaks at 1200 and 990 cm-1, which were assigned for the P=O and C-O-P vibrations, respectively. The phosphorylated corn starch adsorbed methylene blue up to 73.3% and mercury up to 73.6%, indicating the prospect of the microwave-assisted synthetic phosphorylated corn starch as an effective adsorbent for heavy metals.