When the expert speaks of “coffee refinement”, he often means roasting. Because only through this process do the coffee beans get their unmistakable aroma. Therefore “roasting” and “grinding” are also referred to as “refinement”. The different origins are mixed in industrial production before the roasting process so that they always have the same taste profile after refinement.
What does “roasting” mean in the world of coffee?
This process is the important final step on the way to refining the coffee beans. Incredible but true: a coffee bean consists of around 300,000 to 400,000 cells. These are so to speak “activated” by roasting. During roasting, extremely complex chemical reactions take place when the heat is applied. Sugar and amino acids are reassembled, so that an estimated 1,000 new aromas are created in the form of chemical compounds during the roasting process. This fact makes roasted coffee one of the most aromatic foods, and it therefore has far more aromatic substances than wine.
The processing steps in detail
The harvest and its various processes
The coffee harvest season runs from November to April. During this period, the coffee pickers have to make several “picking rounds”, as even the coffee cherries from the same bush ripen at different speeds. Nowadays coffee is harvested using the “stripping” or “picking” method.
The picking process
The branch of a coffee plant can have flowers as well as ripe and unripe fruits at the same time. In order to be able to harvest only the red and fully ripe fruits, manual labor is the only possible harvesting method. “Picking” bears this name because the pickers “pick out” the ripe coffee cherries here. Fruits that are not yet ripe stick to the bush so that they can ripen in peace. On plantations with this method of working, the pickers search the plants for fully ripe fruits at regular intervals. This harvesting process is the most time-consuming, labor-intensive and of course the most expensive type of harvest. However, it guarantees the exclusive use of fully ripe fruits, which can then be optimally processed. In order to maintain the goodness of the quality, the beans must be further processed within 24 hours.
The stripping method
This approach is entirely the opposite of carefully harvesting using picking. The fruits of the branch are completely picked. Therefore, the best time for stripping is when as many fruits of the coffee plant as possible are ripe. At the end of this harvest, only the bare branches remain on the plantation, as the pickers strip them off, including all fruits and leaves.
The use of machines, mostly on flat plantations, is also not uncommon. They are provided with counter-rotating brushes that also remove all fruit and leaves from the branches. Either the fruit will be caught by the machine or they will fall to the ground, and they may ferment and start to rot in no time at all.
The process is accelerated by soil organisms that penetrate the pulp and can even cause diseases. In the process, a single fruit involved in the fermentation process can ruin a large amount of healthy coffee beans. To prevent this, the farmers use electric sorting machines, which for the most part recognize bad fruits, sort them out and dispose of them. Since in the course of the stripping process not only fully ripe, but also overripe and unripe coffee beans are harvested, this yield is sold at a low price.
From raw coffee to finished roasted coffee
Green coffee is called raw coffee. These are coffee beans before they are subjected to the roasting process. Green coffee is usually sorted by size and quality before it is stored and roasted at a later date. After the harvest as well as during processing and further processing, the product is considered green coffee. It is then exported to the corresponding countries and brought to the roasting plants, where the green coffee is finally refined into roasted coffee. The expert calls this phase “preparation”.
The different possibilities within coffee preparation
1. Wet processing
This process is an extremely water-intensive type of coffee processing. In the first step, inferior or unripe coffee cherries are sorted out and then the peel is removed from the coffee cherry. Then the pulp of the cherry is separated from the coffee bean. These steps require different washing processes with a very high proportion of water. Ultimately, only the parchment sleeve and the layer of mucus remain. Then the fermentation process takes place in large tanks.
The fermentation is a biological process, in which ferment organic materials with the use of fungi, bacteria or enzymes added. Bacteria are added to coffee beans for this process. These remove the remains of the sticky parchment skin from the beans and also dissolve small residues from the pulp.
The professional again distinguishes two types within fermentation :
The wet fermentation: this is where water is added to the tanks. In this way the fermentation process is started.
Dry fermentation: With this, the moisture of the depulped coffee bean is sufficient to cause the fermentation process.
After fermentation, which, depending on the amount of added microorganisms and the temperature in the fermentation tanks, can take between 12 and 36 hours, the beans are washed again, whereby the parchment cover can now be easily removed from the beans. They then have to dry in the air in drying stations, or drying machines take over this phase.
The taste of coffee with wet-processed beans is often lively, with a mild body and pleasantly present acidity that causes a slight tingling on the tongue.
2. The dry preparation
In this procedure, water is only used in the first step. This is where the coffee cherries are washed and thoroughly cleaned. They are then placed on special mats and exposed to the heat of the sun for about 2 to 3 weeks. The pulp and skin still adhere to the individual bean. By turning it several times during the drying process, the pulp and skin loosen. At the end of this phase, the parchment-like shell, the silver skin and the pulp can easily be separated from the coffee bean by machine. There is no fermentation with dry processing. At the end of the work step, the coffee beans must be washed and sorted again.
The coffee made from dry-processed coffee beans has a floral scent and impresses with a fruity, slightly floral aroma. Furthermore, these types of coffee are characterized by a complex body.
3. The semi-dry preparation
This procedure is also called ” pulped natural “. The process is similar to dry processing. However, not the whole coffee cherry is dried here, but only the depulped core, i.e. the pure coffee bean. Even with the semi-dry preparation, there is no fermentation.
The coffee prepared in this way has an intense, complex aroma. The flavor is called ” umami “, which translates as “hearty” or “meaty”. With this pleasure, a feeling of soft, full and delicious density develops on the tongue and creates less of a special taste sensation.
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In principle, a distinction is made between hot air roasting and drum roasting.
A. The hot air roast
Here, the coffee is shock-roasted in just a few minutes at very high temperatures of up to 600 degrees Celsius. This is often used to process types of coffee that you can buy inexpensively in supermarkets.
B. The drum roast
In this process, small amounts of coffee beans are gently roasted at low temperatures. This gives the aromas enough time to fully develop. By the way, coffee roasting in a drum roasting oven is the oldest method still in use and the traditional form of long-term roasting. Regardless of the size of the drum, the principle of this type of roasting is always the same: horizontally rotating drums are heated from the outside and whirl the beans evenly around one another.
Since every type of coffee is different, the master roaster’s skills come into play here. Because he has to use his experience, his specialist knowledge, in short his “feeling for the bean” based on the color and the “ cracking ” of the beans to determine exactly when the coffee is ready to roast. Depending on the desired degree of roasting, this process can take up to 20 minutes at temperatures between 180 degrees Celsius and 210 degrees Celsius. Because of this slow and gentle roasting process, the green raw coffee beans are turned into aromatic coffee beans. Chlorogenic acids are largely broken down during drum roasting.
Single origin or blend?
One could also speak of ” single-origin coffees ” or ” coffee blends “. With Single Origin, all coffee beans come from the same growing area and must not be mixed with other types of coffee. These are always exclusive products with an exceptional taste. This is not least due to the type of roasting, as the beans are only lightly roasted. This shows off the multi-faceted taste particularly well. Single origins have an extremely high quality standard, as only the best beans from a harvest are selected for them. The price level for the Single Origin is correspondingly high.
Blend, on the other hand, is a mixture of different types of coffee. They are the most widely used form because it is easy to get a consistent taste in coffee blends. In order to reduce costs, blends are occasionally added to coffees of inferior quality. The more varieties are mixed, the more similar blends are in taste, which means that the richness of taste is lost.
The low price level of the blends in contrast to single-origin coffees is probably the reason why the most popular coffees in Europe consist of blends.
Conclusion: coffee processing
Only the roasting process, the last important step, refines the coffee.
- The picking harvest process is the most labor-intensive, time-consuming procedure and therefore the most expensive method of coffee harvesting
- Within coffee preparation, a distinction is made between wet preparation, dry preparation and semi-dry preparation
- For roasting, there is drum and hot air roasting
- Blends, i.e. coffee blends, are sold the most in Europe compared to single origin for reasons of cost