Cow parts (ear ;ox tail; minced meat)

The sample was very dry; only the root fragments was showing avery fatty, greasy consistency. For fragments > 8 cm, manual precutting was performed with a large kitchen knife. Also, a gardening scissors would be possible to use for precutting.

We used our Universal Cutting Mill PULVERISETTE 19 (50-700 rpm) for precutting the sample to < 4 mm.

The fragments were fed piece wise; it took 30 seconds until all sample was transferred into the grinding chamber. After one minute of grinding, already 60 grams of output was achieved. After finally two minutes, output rose to 67 grams. Surely a longer grinding time might increase the output somehow.

Because of the low dead volume, the grease of the root fragment smeared above knives or sieve cassette. A previous chilling / embrittlement of the fat should produce even less residues. For a rapid cleaning of the grinding chamber, we used small wood chips for small animal bedding and ground a portion with a small perforated sieve cassette. Greases were bound and dust residues were vacuumed off with a soft brush.

First, we tried to grind the precut sample of result one without a previous embrittlement. Because after 10 seconds, no significant comminution was achieved, the trial was aborted.

The sample was transferred into our stainless-steel grinding vessel to comminute after LN2 embrittlement. We poured in some liquid nitrogen to cover all sample and swiveled the vessel until the majority of LN2 was evaporated. The knife was still spinning freely (no sample froze to the bottom of the vessel). We closed the vessel with the lid and started our grinding trial with 2000 rpm in short intervals of one second. Now all LN2 was evaporated and we programmed a comminution of five cycles at 10.000 rpm for 5 seconds per each.

After a total grinding time of 20 seconds, the sample was still frozen and we ground the sample in 2 sec. intervals with 10.000 rpm speed. After finally 30 seconds of high speed grinding, the sample appeared to be very fine. While packing, we found a few fragments with a max. length of 2-3 mm; most likely some tendon fragments which were not embrittled in LN2.

200 grams of minced meat sample were placed into our stainless steel grinding vessel. We poured some liquid nitrogen into the bowl and swiveled the bowl. Because of the rest of moisture inside the sample, the movement of the knife was blocked. The sample was frozen to the bottom of the vessel. We mobilized the sample (with a wooden peduncle) again and waited until the majority of LN2 was evaporated.

The used SOP was programmed to comminute the sample in five cycles of 1 second at 2000 rpm, followed by three cycles at maximum speed (5 sec. per cycle).

A fine powder was achieved which stuck to all available surfaces. The brushed off sample was placed into a glass beaker to check the consistency of the sample after it melted again. We found a few small fragments with ~ 3 mm length on the bottom of the glass (most likely some tendon fragments).

The minced meat sample can also be ground without an embrittlement. For such an application, we provide a sickled knife with serrated blades.

290 grams of sample were used for this trial. We programmed a grinding time of 60 seconds at 10.000 rpm speed. At the beginning, we stopped the mill in short intervals and compressed the vessels volume with our vario-lid. After 15 seconds, the lid was pushed down to its maximum and we proceeded grinding with a light variation in height.

After the first 30 seconds of total grinding time, we stopped the mill and took one photo of the fine ground sample material. The sample appeared to be very homogenous. A stretched-out sample has shown a few fragments with 1-2 mm length (tendon like material).

We placed the complete sample back into the polycarbonate vessel and ground the sample for further 30 seconds. The ground sample was very sticky to the vessel and led, still some 1 mm long fragments were observed. The sample temperature rose to ~ 40 °C at this point. Most likely, also those tendon-like fragments will not be ground significantly finer this way.

We packed the sample and cleaned the grinding equipment by placing a proper portion of water and surfactant into the bowl. After 30 seconds of high speed “milling”, the equipment was flushed with fresh water and dried off.

The ox tail sample was precut with gardening scissors to < 2 cm length. Even with LN2 embrittlement in our Knife Mill PULVERISETTE 11, the sample was not ground. Only some small, chipped off fragments were found after a few seconds. A Universal Cutting Mill PULVERISETTE 19 was required to precut this type of sample.

The still frozen sample material was placed into the protected funnel with pusher and transferred into the grinding chamber in one batch. The grinding sound vanished rapidly. After 10 seconds, no further grinding sound was recognized.

Only a few loose particles remained inside the grinding chamber and have been removed rapidly by vacuuming with a soft brush.

A grinding of LN2 embrittled sample failed with our Knife Mill PULVERISETTE 11. The still frozen sample material was taken out of the vessel and was used to grind the sample with our Variable Speed Rotor Mill PULVERISETTE 14 classic line.

With impact and shearing forces, the sample might be comminuted as desired.

We used a sieve ring with 1,0 mm trapezoidal perforation and fed the sample into the mill which was equipped with an 8 rib rotor and which was running at 20.000 rpm. It took us ~ 25 seconds until the 55 grams of sample were transferred into the mill (spoon wise). The grinding sound stopped instantly after a spoon of sample passed the feeding funnel.

After 30 seconds, the mill was stopped. The ground sample almost filled the standard collecting vessel. The 1 mm sieve ring was not clogged significantly. Most likely, even smaller perforations can be used (0,75 mm or finer) for grinding. Only a few fibrous residues were located above the rotor ribs. For higher amounts of sample, we recommend using one of our cyclone separators. Cleaning was performed rapidly by vacuuming with a soft brush.