Nov 30, 2017· In brief, about 1 g the extractivesfree sample was loaded to 50 mL ZrO 2 grinding jar (including 10 × 10 ball bearings) in Retsch Ball Mill PM 100. The biomass was then ball milled at 580 RPM in a frequency of 5 min with 5 min pauses inbetween for h total time.