Starch was isolated from sweet potato and the process was standardized. It was found that the treatment ‘T8’ containing (0.25% potassium meta-bisulphite (KMS) and 0.12% citric acid) had shown excellent and promising result so far as residual protein, yield, past clarity and colour of the isolated starch was concerned. Chemical modification of isolate sweet potato starch at 3% and 5% (w/v) levels was carried out by acetylation using vinyl acetate concentration (4 to 10 %) and dual-modification using propylene oxide at a specific level of 7% and adipic acid anhydride (0.05 to 0.12%). Biodegradable films were prepared from the isolated native and modified starches. Glycerol at levels such as (0.25g/g, 0.35g/g, and 0.45g/g) was used as a plasticizer in the film preparation. Thickness of bio-films increased with increase in glycerol and starch concentrations whereas solubility decreased with increase in starch concentration and modification levels. Water and acid solubility of films prepared from native starch were highest which decreased in the acetylated starch films and further decreased in cross-linked starch films. With increase in starch and glycerol concentration tensile and puncture strengths of bio-films increased. Dual-modified starch films had shown higher mechanical strength than acetylated starches. The biodegradability was higher for native bio-films followed by acetylated starch and least for dual-modified films.
Chemical Modification of Potato Starch by Graft Copolymerization with Citronellyl Methacrylate
