Synthesis and characterization of corn starch esters obtained in oleic acid/L(+)-tartaric acid medium

Abstract

In this study, corn starch esters were obtained by a novel methodology using oleic acid as an esterifying agent and L(+)-tartaric acid as both catalyst and esterifying agent. The degree of substitution (DS) was determined along the reaction time to control the level of substitution achieved (up to 0.33), while all the other reaction parameters were maintained constant. Several techniques were applied to characterize the starch esters obtained, namely, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermogravimetry (DTG), differential scanning calorimetry (DSC), proton nuclear magnetic resonance spectroscopy (H NMR), polarized light microscopy, and X-ray diffraction (XRD). The incorporation of ester groups causes a gradual decrease in the crystallinity and thermal stability of the substituted starches. The hydrophobicity of the samples increases significantly as a function of the DS obtained. ¹H NMR analysis and solubility in dimethylsulfoxide (DMSO) indicate that the L(+)-tartaric acid is involved as a catalyst and an esterifying agent that crosslinks starch chains. The materials obtained are promising for use in various applications such as emulsifiers, surface coating materials, flavoring agents in the food industry, and biomedical applications for bone fixation and replacements, among others, meriting future studies.