The influence of dry heat treatment on the structure and performance of thermoplastic starch with different amylose content

Dry heat treatment (DHT) was used to physically modify high-amylose starch, normal starch, and waxy starch, and the three modified starches were then prepared into thermoplastic starch (TPS) via the melting method. The effects of DHT duration on the structure and properties of TPS with different amylose content were investigated by analyzing the crystalline structure, molecular structure, rheological properties, mechanical properties, and light transmittance. FTIR and dynamic rheological results showed that as the DHT duration increased, the short-range order and solid-like behavior of the three types of TPS improved. Waxy TPS exhibited the most significant improvement in short-range order, while normal TPS showed the most noticeable enhancement in solid-like behavior. The crystallinity of high-amylose TPS increased with prolonged DHT, whereas waxy TPS exhibited the opposite trend. After DHT modification, both the UV barrier performance and tensile strength of all three materials improved, with high-amylose starch showing the most significant changes. The differential effects of DHT modification on TPS with varying amylose content are expected to expand the industrial application range of starch-based materials. This study provides a theoretical foundation for the application of DHT in the preparation of thermoplastic starch materials. ● The starch modified by dry heat was plasticized by melting method. ● The amylose content influences the effectiveness of dry heat treatment. ● The short-range order of the modified materials is improved. ● The treatment can improve the strength and UV barrier of thermoplastic starch.