Determining significant reaction parameters for cassava starch (Manihot esculenta) esterification with long-chain fatty acid chlorides in an aqueous solution

An important strategy for a highly efficient method to esterify cassava starch with a long-chain hydrophobic acyl group in aqueous solution was reinvestigated. Most of the published reports relied on the elevated reaction temperature in order to disperse and gelatinize starch which negatively affects the esterification. To promote the esterification completion within a short reaction time, lower reaction temperature was employed which is made possible by an efficient method of cassava starch dispersion by NaOH (aq.). The low temperature reaction conditions were explored and found to improve the starch esterification efficiency in aqueous solution. The other reaction parameters including NaOH concentrations, reaction time, and fatty acid chloride chain lengths were also investigated. Low reaction temperature enhances the degree of substitution up to 0.31, and the yield to a range of 50–56%. The results indicate that the conditions for setting up a successful esterification reaction with high reaction efficiency are: i) low reaction temperature (4°C); ii) up to C12 fatty acid chloride; and iii) low NaOH concentration (1.0–1.5M).