This study investigates the synthesis of corn starch nanocrystals (SNCs) via sulfuric acid hydrolysis. Esterification of oleic acid (OA) with SNCs was carried out using Maghnite-H+ as a catalyst, a non-polluting, eco-friendly proton-exchanged montmorillonite-based green catalyst suitable for various chemical processes. Optimization of synthesis parameters, including reaction temperature, duration, and catalyst quantity, was conducted using response surface methodology (RSM) with a central composite design incorporating three factors and three levels. Optimal conditions for achieving a high degree of substitution (DS) were determined as follows: 21.27 h reaction time, 106.39 °C temperature, and 15.17 % (by weight of starch) Maghnite-H+ catalyst, with a molar ratio of OA to anhydrous glucose units of 3:1. Characterization of the esterification product was performed using FTIR spectroscopy, while electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed significant changes in appearance and internal structure post-esterification. Thermal analysis indicated lower heat resistance for SNCs-OA compared to native starch and SNCs. Furthermore, both esterified and unmodified SNCs exhibited antioxidant properties, with activity comparable to standard antioxidant vitamin C (ascorbic acid), as measured by their ability to neutralize free radicals, which increased with SNCs concentration. This comprehensive study offers valuable insights into the synthesis, characterization, and functional properties of SNCs-OA.
Keywords: Antioxidant properties; Box-Behnken; Esterification; Maghnite-H(+); Oleic acid; Starch nanocrystals.
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