Abstract: Rice starch was milled for 5, 10, 20, 30, 60, 90 or 120 min using a high-energy ball mill and then characterized by rapid viscosity analyzer, differential scanning calorimetry, laser particle size analyzer, scanning electron microscopy, polarizing microscopy, X-ray differaction (XRD) and Fourier transform infrared spectrometer. The results showed that peak viscosity, trough viscosity, breakdown value, final viscosity, setback value and gelatinization temperature decreased from 6.80, 3.75, 3.06, 5.35, 1.61 Pa·s and 81.00 ℃ to 2.33, 0.49, 1.84, 1.06, 0.57 Pa·s and 68.07 ℃ after 30 min milling, respectively, and then leveled off with increasing milling time. The phase transition peaks G and M1 were both weakened with the increase in milling time, and they completely disappeared when the milling time exceeded 30 min. The structural analysis showed that the crystalline structure of rice starch gradually diminished with ball milling up to 30 min, and was finally almost completely destroyed. Moreover, 5 and 10 min ball milling could cause irreversible expansion of starch granules to some extents, and ball milling for over 20 min broke down the starch granules, causing them to aggregate. The high-energy ball milling treatment changed the structure and conformation of rice starch, but did not lead to the formation of new chemical bonds and groups.

Key words: rice starch, high-energy ball milling, physicochemical properties, structure