Synthesis and characterization of citric acid esterified rice starch by reactive extrusion: A new method of producing resistant starch

摘要

Citric acid-esterified rice starch was synthesized using a one-step reactive extrusion method. The structure, physicochemical properties, and digestibility of the esterified starch were then measured. An in vitro digestion study indicated that esterification significantly increased the level of resistant starch (RS) in the samples. Fourier transform infrared spectroscopy (FT-IR) confirmed esterification had occurred between the citric acid and starch, with a new peak appearing at around 1730 cm(-1). X-ray diffraction indicated that esterification caused a decrease in the degree of crystallinity in the starch. The swelling power and solubility of starch citrate were both lower than unmodified starch. Turbidity measurements suggested there was a slower rate of reassociation in starch citrates during storage. These results suggest that citric acid esterification promoted cross-linking within the starch that significantly reduced its digestibility. This simple method may be useful for the creation of healthier starchy foods.