High-pressure solid-state (mechanochemistry) synthesis of corn starch tartrates

In this work, native and pretreated corn starches were chemically modified to obtain starch tartrates, a derivative with potential use in a variety of food and non-food applications, such as biomedical, pharmaceutical, and environmental fields. The objective was to perform the synthesis by a novel solid-state methodology at high-pressure, varying the system pressure, temperature, and reaction time. Before the reactions, native starch was thermally pretreated in a water/propylene glycol medium to improve the esterification activity. The maximum degree of substitution (DS) reached (0.1718) was achieved using native pretreated starch at a pressure of 55 kg cm^-2, a temperature of 343 K, and a reaction time of 72 h. To characterize the derivatives obtained, several techniques were used, such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermogravimetry (DTG), differential scanning calorimetry (DSC), polarized light microscopy, and X-ray diffraction (XRD). The obtained results demonstrate that it is feasible to carry out the solid-state esterification of starches using a high-pressure system, achieving higher DS than the system at atmospheric pressure. Furthermore, starch pretreatment improves the reaction performance (up to 34% for the maximum DS) compared to that achieved using native starch.