Investigation of rheological properties and conformation of cassava starch in zinc chloride solution

Zinc chloride aqueous solution is a non‐derivatizing solvent for starch, and can be used as a media for homogeneous starch modification. Here, the rheological properties of starch in ZnCl2 aqueous solution under different conditions are considered. Specifically, a large number (120) of viscosity–shear‐rate curves for starch–ZnCl2 solutions with different starch contents, ZnCl2 concentrations, and temperatures were obtained and modeled using a master curve method. In particular, the power‐law index (n) from the modeling could accurately classify the starch molecules in ZnCl2 aqueous solutions into an insoluble state, a dilute state, a semi‐dilute state, and a sticky state, reflecting the different degrees of chain interactions in the solution. In particular, the sticky state would be mostly likely be controlled by the zinc–starch complex, which made the rheological behavior entirely different from that at low ZnCl2 concentrations. The knowledge obtained from this study can be used to guide the homogeneous modification of starch and the fabrication of starch‐based materials using green solvents such as aqueous ZnCl2 with desired properties. \n \n