Optimization of starch oleate derivatives from native corn and hydrolyzed corn starch by response surface methodology

Conditions for the preparation of starch oleates of native and hydrolyzed corn starch were compared with the aim of developing a hydrophobic starch as gum arabic substitute for use as a wall material in microencapsulation. Optimization of the reaction parameters for maximization of degree of substitution (DS) of starch oleate was carried out using response surface methodology (RSM). Corn starch and maltodextrins of dextrose equivalent (DE) 12 and 18 were used in the study. A central composite rotatable experimental design (CCRD) was chosen to explain the combined effects of the three parameters, viz., oleic acid concentration, reaction time and reaction temperature to design minimum number of experiments. The optimal levels of the three parameters for corn starch (50 g) were an oleic acid concentration of 1.2 g, a reaction time of 201 min at 160 °C, wherein a maximum DS of 0.021 was obtained. For maltodextrin of 12 DE, 1.53 g oleic acid concentration, a reaction time of 334 min at 150 °C gave a corresponding DS of 0.0353. Similarly, for 18 DE, 1.36 g oleic acid concentration, a reaction time of 300 min at 129 °C gave a DS of 0.053. The optimized samples were compared to gum arabic with respect to emulsifying capacity.