The chemical modification of a range of starches under aqueous reaction conditions

A series of starch esters with different side-chain lengths and moderate DS-values was prepared and studied. The esters were prepared by acylation of the gelatinised starch with the appropriate acid chloride in 2.5 M aqueous sodium hydroxide (NaOH) solution, which represents an economical and facile method for the preparation of esterified starches. The alkali solution acted as the medium for the derivatisation and ensured uniform substitution by enhancing solubility of the starch and accessibility of the reagent. Successful esterification was limited to acid chlorides containing between six and 10 carbon atoms. Shorter or longer chain-length acid chlorides did not react under these conditions to form esters, as confirmed by FT-IR spectroscopic and elemental analyses, as well as by intrinsic viscosity analysis.