A Thermomix® is a miracle weapon for chopping and grinding food in the kitchen. Therefore, it's not surprising that many households also use a Thermomix® to grind coffee. While this is possible in principle, it doesn't guarantee good coffee.
The Thermomix® is a master of chopping, but it doesn't grind; it slices. It's not equipped with grinding discs, but rather with chopping blades, which, depending on the length of chopping time, can achieve almost any grain size of coffee, vegetables, nuts, etc. Unfortunately, the precision isn't sufficient for truly good coffee. In addition, the surface texture of a crushed coffee bean looks different than that of a ground coffee.
The coffee grind curve in an espresso grinder looks roughly like this. This degree of precision cannot be reliably adjusted with the Thermomix®. Although the coffee is ground, the degree of fineness or coarseness varies from grind to grind.
Why does the coffee from the Thermomix® sometimes taste sour and sometimes bitter?
The varying taste is due, on the one hand, to the uneven particle distribution (number of grain sizes). This varies from grind to grind, as the coffee grinders don't always grasp the coffee beans in the same way. This is also due to the fact that coffee has a different density depending on its origin. The size of the beans also varies depending on the variety, type, and growing region.
Cutting and breaking the beans results in a relatively large particle dispersion. This is important because finer particles tend to extract too much, resulting in bitterness in the coffee . Coarser particles are less easily extracted by the brewing water. This leads to under-extraction and thus a sour, aggressive taste in the cup.
If both fine and coarse particles are present, this results in a mixture of bitterness and acidity that tastes particularly unpleasant.
Is a Thermomix® not suitable for coffee?
That's not a general statement. There are some very satisfied users who successfully use the Thermomix® to brew filter coffee. Those who know their Thermomix® well and use good coffee have a huge advantage over supermarket coffee. This is often pre-ground and therefore already has a lower quality.
Coffee ground with the Thermomix® is always better than pre-ground coffee from the supermarket!
However, we recommend using Thermomix® ground coffee for filter coffee. The precision of the particles is not quite as crucial for filter coffee as it is for espresso. With filter coffee, the contact time between the coffee and water can be controlled in other ways than just by adjusting the grind size.
Espresso with the Thermomix®?
When it comes to espresso, the precision of the grind is crucial. This is almost impossible to achieve with the Thermomix®. But there's a trick here, too! For once, the so-called "double-walled sieves" make sense. These are included with cheaper espresso machines. The sieves themselves have only a small opening through which all the ground coffee is squeezed. This way, the sieves create the resistance that pre-ground coffee can't.
A good espresso takes about 20-30 seconds to brew . Thanks to the double-walled sieve, this can be achieved with almost any coarsely ground coffee or even older coffee. If we use the Thermomix and don't grind too finely, we can use the double-walled sieve. This gives us a good extraction time. The espresso won't be as perfect as with a properly adjusted espresso grinder , but the result will be good enough for the coffee used.
