Abstract: Parameter optimization for the superfine comminution of Astragalus membranaceus root by vibration-milling was carried out based on cumulative distribution rate of 400 mesh superfine powder (Va). The physical properties of superfine Astragalus membranaceus root powder were studied at different levels of granularity. Results showed that superfine comminution increased the fluidity, water binding capacity, expansibility and bulk density of Astragalus membranaceus root. The maximum dissolution rate of total flavonoids from superfine A. membranaceus root powder of 400 mesh was 0.26 g/100 g. The optimal superfine comminution of Astragalus membranaceus root was achieved through dry comminution on high-speed pulverizer for 1 min, sieving through a 60 mesh sieve, moisture content adjustment to 6.7% and superfine comminution at － 20 ℃ for 20 min. As a result, a Va of 86.9% was obtained. Moisture content had the greatest effect on Va, followed by comminution time and temperature. Moreover, a regression model for Va (Y) as a function of temperature (A), comminution time (B) and moisture content (C) was obtained as follows: Y = 85.62 + 0.085A + 1.22B － 3.48C + 1.05AB + 0.35AC + 0.63BC － 2.28A2－ 4.18B2 － 2.73C2.

Key words: Astragalus membranaceus, superfine comminution, cumulative distribution rate, property, process optimization