Study of Kinetics, Thermodynamics and Reaction Time of Corn Starch Acetylation 

Abstract

Starch acetylation plays a crucial role in the starch industry, offering enhanced versatility and functionality. The study aimed to analyze the kinetics and thermodynamics of starch acetylation. Corn starch was acetylated in different degrees of substitution by esterification reaction with acetic anhydride, acetic acid and sulfuric acid as a catalyst. Order of the reaction was determined by integral analysis method, defined as a pseudo-first order because it presents correlation factor R2 closest to 1. From thermodynamic models used, it was possible to determine enthalpy of acetylation (-1.33x10-2 J.mol-1), critical temperature (0.0223 K), heat capacity (1.53x10-3J.mol-1.K-1) and entropy change (-2.31x10-4 J.mol-1.K-1). Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) characterized starch and starch acetates. In analysis, acetylation was confirmed with the appearance of band at 1740 cm-1, corresponding to carbonyl of acetyl group, presence of pores and breakdown of starch granules after acetylation reaction. Starch acetylation increased with reaction time, reaching a maximum degree of substitution of approximately 2.62 after 50 minutes.