Preparation and characterization of corn starch straws with strong mechanical properties by extrusion and retrogradation

The large consumption and subsequent discarding of disposable plastic straws can cause serious harm to the environment and pose a potential threat to human health. The aim of this study was to prepare a new straw from edible and degradable corn starch (CS) by twin-screw extrusion combined with starch retrogradation. The retrograded CS straws showed excellent mechanical performance (high flexural strength of ≈ 14000 g) and sufficient hydrostability (22.9 times the wet mechanical strength of CS straws) after soaking in 25 ℃ water for 1 h. The retrogradation treatment increased the crystallinity of starch straw from 22.01% to 29.64%, and had no significant effect on the thermal properties of starch. The CS straws and commercial rice straws, after soaking in water for 1 h, showed a bent appearance that negatively affected their consumer use. The CS straw with 30% moisture content and retrograded for 6 h remained vertical after soaking for 12 h. The stiffness of retrogradation starch straw soaked in orange juice for 30 min was up to 9500 g/sec. Considering the wide source of raw materials and low cost, corn starch straws strengthened by retrogradation are expected to serve as suitable substitutes that will solve the environmental challenges caused by the extensive use of plastic straws.