Bee propolis

For our test we used approximately 350 ml of pre-cut sample. The total available volume of the vessel is higher, but we don’t recommend using more than 500 ml of sample, because the speed of the knife will be limited when too much of sample is fed.

Before the sample was fed, the steel vessel was pre-chilled with a bit of liquid nitrogen. After the cooling down of vessel and knife we added the sample to the vessel and added more liquid nitrogen in order to embrittle the sample.

The vessel was tilted so liquid nitrogen was covering all the sample. After about 30 seconds, the majority of the liquid nitrogen was evaporated and we ensured that the knife was still possible to move.

The vessel was closed with the lid and placed in the mill was. We programmed five cycles of a grinding with maximum speed (10.000 rpm) for one second, followed by a programmed pausing step of two seconds. The observed grinding sound was smooth; a tiny amount of dust escaped the Cryo-lid inlay (a filter with approx. 100 µm passage).

After five cycles (and five seconds of total grinding time), we inspected the grinding vessel. A typical grinding result was observed; majority of sample was comminuted quickly to a fine powder (mainly about 100-300 µm) with a few larger fragments (up to ~ 500 µm max.). The achieved fineness is typical for a Knife Mill PULVERISETTE 11.

After emptying the vessel, some fine sample dust remained on the lid and inside the vessel. We wiped off the residue with a cloth damped with alcohol and finally used warm water and soap inside the mill.