Impact of extrusion cycles on the multi-scale structure, physicochemical properties, and functional behavior of high amylose starch

Starch is one of the most industrially significant biopolymers, with extensive applications in food industry. Its technofunctional and physicochemical properties are largely determined by the amylose-to-amylopectin ratio. This study evaluated the impact of extrusion cycles on the multi-scale structure, physicochemical, thermal, and pasting properties of high-amylose starch (HAS). It was used a thermally stable, and industrially relevant HAS "Hylon VII (R)". Material was subjected to extrusion cycles at 125 degrees C and 15 rpm using a single-screw extruder. The extrusion cycles progressively induced changes in HAS properties, while the granule morphology remained intact until the second cycle. Thermal analysis revealed minimal changes in gelatinization properties during the first two cycles, underscoring the high thermal resistance of HAS. Additionally, solubility and water absorption capacity increased by approximately 40 % compared to native HAS after the second extrusion cycle. X-ray diffraction patterns showed a transition from a B-type to a V-type structure after three extrusion cycles, indicating partial structural rearrangement. These findings demonstrate that HAS can withstand substantial thermomechanical stress while retaining its functional properties up to the second extrusion cycle. The observed structural modifications also suggest an enhanced potential for interaction with water, presenting opportunities to tailor its functional properties for specific industrial applications.