Pre-Esterification Dry Heat Treatment Enhances the Functional Properties of Starch Citrate: Enzyme Resistance and Water Absorption.

This study investigates how pre-esterification dry heat treatment (DHT) of corn starch at 170°C, 180°C, and 200°C influences the functional properties of subsequently synthesized starch citrates. Structural and morphological changes induced by DHT and esterification were analyzed using scanning electron microscopy, X-ray diffractometry, and Fourier-Transform Infrared spectroscopy. Starch citrates were characterized for their resistance to pancreatic α-amylase and amyloglucosidase, as well as their water absorption capacity (WAC) at 37°C. Results demonstrated a strong correlation between DHT temperature and the functional properties of the final citrate. Increasing the DHT temperature significantly increased the resistant starch fraction and WAC. Specifically, citrates from native starch had a resistant starch (RS) fraction of 91%, while citrates from starch pre-treated at 200°C exhibited a markedly increased RS fraction of 98% and a 64% increase in WAC. These findings indicate that DHT is an effective pre-treatment for enhancing the dietary fiber potential and hydration properties of starch citrates.