Effect of Pullulanase Pretreatment on the Water Resistance and Mechanical Properties of Starch Straws

ABSTRACT To explore the impact of pullulanase pretreatment on starch straws, the study examined and analyzed the structure, water resistance, and mechanical properties of the straws by varying the levels of pullulanase addition (0%, 0.02%, 0.06%, and 0.08%). The study found that pullulanase pretreatment increased the weight‐average molecular molar mass (Mw) of starch straws from 1.37 to 4.32 × 105 g/mol by enhancing amylopectin's shear resistance during thermoplastic extrusion. Additionally, the pretreatment improved the crystallinity (increasing from 9.72% to 16.24%) and short‐range order of the starch straws, as confirmed by x‐ray diffraction (XRD) and Fourier transform infrared (FTIR) results. The increased crystalline structure in pullulanase‐pretreated starch straws (pullulanase addition ≤ 0.06%) improved the compactness of their internal structure, thereby enhancing mechanical strength and water resistance. Conversely, 0.08% pullulanase induced microcracks that compromised structural integrity, reducing both performance metrics. This study demonstrated the potential of pullulanase pretreatment to improve the usability of starch straws.