Abstract: This study investigated the effect of freezing ball milling treatment on the structure, properties and digestibility of waxy rice starch, prepared by alkaline extraction. The effects of treatment time on the particle size distribution, microstructure, crystalline structure, short-range ordered structure, pasting properties, thermodynamic properties and digestibility of waxy rice starch were examined. The results showed that after freezing ball milling treatment, the integrity of starch granules was damaged with cracks appearing on the surface, the particle size tended to increase, and the crystalline structure and short-range ordered structure were severely damaged. The water absorption index increased from 2.15 to 7.31 g/g, and the cold water solubility and swelling power increased significantly from 2.97% and 3.25% to 46.33% and 15.50%, respectively in the 80 min ball milling group compared with untreated samples (P < 0.05). The enthalpy change (ΔH) decreased from 9.33 to 1.79 J/g, and the degree of gelatinization significantly increased (P < 0.05). The birefringence of the starch gradually disappeared with increasing treatment time. The rapidly digestible starch (RDS) content of waxy rice starch increased significantly (P < 0.05), while the contents of resistant starch (RS) and slowly digestible starch (SDS) decreased significantly (P < 0.05). This study provides basic data and references for the production of modified starch products with novel structures and properties.

Key words: waxy rice starch; freezing ball milling; structure; digestibility