Fabrication of high-amylose starch nanofibers via solution blow spinning: Role of starch concentration

Starch nanofibers hold promise for food-packaging but scalable production is hindered by limited spinnability understanding and conventional spinning challenges. Here, solution blow spinning (SBS) was employed to fabricate nanofibers from pure high-amylose starches (HI55 and HI70, with 56% and 72% amylose content, respectively) dissolved in aqueous NaOH, as model systems. Quantitative spinnability windows (non-spinnable, C < C ^⁎, overlap; onset, C ^⁎ < C < C _e; stable, C > C _e, entanglement) were quantitatively established by correlating fiber morphology with rheological transitions. Stable fibers formed only at C > C _e, where sufficiently entangled starch chains formed a viscoelastic network capable of sustaining flow-induced extensional deformation under the combined shear and stretching fields of SBS. The transition from the non-spinnable regime to stable spinnability was accompanied by coordinated rheological responses, including increased consistency index, zero-shear viscosity, critical strain, and structural viscosity index, together with reduced non-Newtonian index, modulus-frequency dependence, and surface tension. In addition, fiber diameter scaled with both surface tension and C / C ^⁎, highlighting the coupled roles of interfacial effects and chain entanglement in fiber morphology. Compared with HI55, HI70 exhibited superior spinnability at lower concentrations due to greater amylose-induced chain entanglement.