Effect of particle size on the physicochemical and antioxidant properties of Forsythia suspensa (Thunb.)Vahl leaf powders

Four powders of Forsythia suspensa leaf were prepared by coarse grinding and subsequent ball milling. The effects of particle size on the physicochemical and antioxidant properties of the powders were evaluated. The results showed that the particle size of the powder decreased from 107.99 to 29.20 μm by ball milling for 5 h. In addition, the ball-milled powders had substantial advantages in water holding, solubility and swelling capacities. Thus, the ball-milled powders had a better dissolution of phenolic, flavonoid, and polysaccharide components (25.45, 1.99 and 44.19 mg/g of powder for 5 h of ball milling), ultimately resulting in a superior antioxidant activity (maximum reductions of 14.96% and 19.20% for DPPH and ABTS radicals, respectively). The FTIR analysis showed that the structure of the active ingredients remained intact after ball milling. In conclusion, ball milling is a promising technique for preparing Forsythia suspensa leaf powder with improved physicochemical and biological properties. • Forsythia suspensa powders were obtained by coarse grinding and ball milling. • The properties and activities of the powder are correlated with the milling time. • The hydration properties of ball-milled powders rise with decreasing particle size. • Decline of the flow and thermal properties after ball milling treatment was found. • Antioxidant activity enhanced with higher active ingredients of ball-milled powders.