Enthalpy relaxation and glass to rubber transition of amorphous potato starch formed by ball-milling

Ball-milling is known to convert native potato starch into an amorphous state. Using differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD), we demonstrated that the ball-milled amorphous starch exhibits a glass to rubber transition accompanied by a recovery from enthalpy relaxation. Such transition behavior differs from that of the glassy starch formed by heating and subsequent quenching. We further found that the ball-milling process for potato starch enhances the enthalpy and volume relaxation with breaking the crystalline inner native potato starch. In addition, our results suggest that WAXD examination may capture the volume relaxation phenomena of amorphous materials such as starch.