Preparation of thermoplastic starch with comprehensive performance plasticized by citric acid

Abstract To prepared thermoplastic starch (TPS) with good thermal plasticization processibility and resistance to retrogradation is important in this field. Herein, TPS plasticized with different plasticizers were successfully produced using a twin‐screw‐extruder. Effects of glycerol, xylitol, and citric acid on the retrogradation properties of TPS were studied by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). It showed that citric acid can improve the thermal plasticization processibility of TPS through three mechanisms, that is, chemical reaction between citric acid and starch, chain fragmentation of starch molecule due to the acidolysis of citric acid, and decrease of interaction between starch molecular chains. Since citric acid can be chemically fixed in the starch, excellent retrogradation resistance was achieved. After the accelerated retrogradation at 60°C/80RH for 48 h, the retrogradation and crystallinity of CA 4 TPS are 0.8% and 4.26%, respectively, which were lower than TPS without citric acid. In this work, a series of TPS samples with citric acid content from 0 to 8 wt% were prepared, and the DSC and XRD results showed that the TPS with 4 wt% citric acid yielded the least amount of retrogradation. The results of this investigation lay a solid foundation for the preparation and application of TPS with excellent performance.