Effect of ethanol ball milling on the structure, properties and in vitro digestibility of corn starch

Ethanol, as a ball milling medium, not only helps improve the uniformity of ball milled modified starch, but also inhibits the swelling of starch particles, while avoiding issues such as agglomeration and high energy consumption associated with wet ball milling for modified starch. Moreover, ethanol is volatile, which can significantly improve the production efficiency of modified starch. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), laser Raman imaging (LRS), differential scanning calorimetry (DSC) and rapid viscometry (RVA) were used to investigate the changes in the structure, properties, and in vitro digestibility of corn starch, verify the feasibility of this method, and explore its mechanism of action. The results showed that after 120 minutes of ethanol-mediated by ball milling, the crystallinity of corn starch decreased from 34.16% to 26.61%; the gelatinization enthalpy of corn starch decreased by 9.49 J/g, with reductions in peak viscosity and final viscosity; the solubility of corn starch increased to 36.6%, the content of free amylose increased, its digestibility rate rose from 74.3% to 85.6%, and the content of RDS increased by 14.1 percentage points. The digestion mode of starch followed a combination of parallel and sequential digestion modes. When subjected to 45 minutes of ball milling, corn starch exhibited increased crystallinity, elevated viscosity, reduced solubility, and enhanced gelatinization enthalpy. This phenomenon arises because the mechanical force generated during ball milling promotes the internal recrystallization of starch. These findings indicate that ethanol ball milling can alter starch structure, thereby significantly modifying the properties and in vitro digestibility of corn starch. The process of ethanol ball milling of starch conforms to the theory of mechanochemistry. Therefore, appropriate ethanol ball milling treatment of corn starch enables most starch particles to remain in the agglomeration stage while enhancing starch’s chemical reactivity. This research provides theoretical and technical support for the future preparation of high-quality modified starch.