Effects of Twin-screw Extrusion Temperatures on Structure and Physicochemical Properties of Corn Starch

Abstract

As changes in the melting behavior of starch in the extruder affect the physical properties of the extrudate. exploring the melting behavior during starch extrusion is of great significant for the production of ideal thermoplastic starch-based materials. Effects of different extrusion temperatures (60, 70, 80, 90 and 100 ℃) on the structure and physicochemical properties of corn starch were investigated. The results showed that under high temperature and mechanical shear, the starch granules were fragmented and the granule size was reduced. The hydrogen bonds within starch molecules were broken, which made starch easier to bind with water molecules, to improve the hydration properties of thermoplastic starch (TPS). As the temperature increased, the content of amylose increased, and the relative crystallinity (RC) and double-helix order (DO) decreased, indicating that the long-range and short-range ordered structures of corn starch were destroyed during heating. The high temperature treatment of the extruder reduced the enthalpy of TPS and destroyed the ability of starch paste to form a gel network. The samples had a weak gelation behavior, and the rigidity and elasticity were weakened. In conclusion, the temperature of twin-screw extrusion changed the starch particle structure, crystalline structure, hydration and rheological properties to different degrees. This study has provided theoretical basis and new ideas for extruding high quality thermoplastic starch materials.

Keywords

• twin-screw extrusion
• thermoplastic starch
• structure
• physicochemical properties