The art of coffee roasting - the path to the perfect bean

The aroma of freshly brewed coffee is aromatic and enticing. Floral, chocolaty, earthy or pleasantly fresh - coffee enchants the senses with over 800 flavours. But how do the different flavours get into the coffee? In addition to the actual beans, their careful care and harvesting as well as the correct preparation, the roasting of the coffee beans is a decisive factor for unrivalled coffee enjoyment. We take a closer look at the art of coffee roasting and explain how coffee gets its unmistakable aroma and its wonderful brown colour.

Coffee roasting starts with the green coffee
Every cup of coffee starts with a small, green, inconspicuous fruit - the coffee cherry. The cherry-like fruits, which we call beans, grow in the so-called coffee belt in sun-kissed countries such as Brazil, Peru, Indonesia, Colombia and Ethiopia. Each region brings its own special characteristics to the fruit, and the two varieties Arabica and Robusta differ from each other above all in terms of intensity. The real art of turning the beans into an aromatic and invigorating drink lies in the coffee roasting process.

Before coffee roasting can begin, the beans are picked from the coffee bush and dried. This is the green coffee. It is greenish in colour, sometimes yellowish or brownish, which has earned it the name "green coffee". The green beans do not smell of coffee at all, but are more reminiscent of green tea. Coffee roasters use this green coffee to extract the legendary taste of the Central Europeans' favourite drink.

The five steps of coffee roasting
When coffee is roasted, the green beans become the basic ingredient for an invigorating start to the morning, a relaxing cup of coffee with afternoon cake or the crowning glory of a delicious evening meal in the form of an espresso. During the roasting process, the colour and structure of the coffee beans change. They turn brown, lose density, increase in volume, decrease in mass and lose around 15 to 20 per cent of their moisture. The art of coffee roasting lies in knowing these chemical and physical changes precisely and influencing them at the right time with the right temperatures. During the roasting process, the coffee beans are slowly heated to temperatures between 180 and 210 degrees.

Stage 1 - Drying
When the coffee beans arrive at the roasting plant, they have a moisture content of around eight to twelve per cent. In the first phase of coffee roasting, the beans heat up slowly and the water begins to evaporate. This is because the temperature in the roasting drum drops to around 90 degrees Celsius as the beans are filled. It still smells of green tea and freshly mown grass.

Stage 2 - Yellowing
In the second stage of coffee roasting, the typical coffee flavours slowly begin to develop. The chemical and physical changes set in and the smell of toasted bread emanates from the roasting drum. This is also when the beans start to change colour. They expand and shed the silver skin, the chaff.

Stage 3 - The first crack
In the third phase, you can not only smell the coffee, but also hear it. The temperature is slowly increased again, the pressure rises and the water evaporates in larger quantities. This changes the structure of the walls of the coffee beans, which is noticeable in a soft cracking sound.

Stage 4 - The development of the roast flavours
Now comes the fourth phase of coffee roasting. It lasts right after the first crack until the end. This is where the coffee roaster's craftsmanship comes into play. The longer the coffee beans are roasted, the more sugar is caramelised and acids are broken down. Depending on the desired degree of roasting and flavour profile, this phase takes between ten and 15 percent of the entire roasting process. In many coffee roasting plants, this is 13 to 25 minutes.

Stage 5 - The final crack
The fifth stage of coffee roasting is characterised only by a final crack. The beans crack a second time, which is also known as the second crack. Coffee roasters do not always wait for this second crack. Depending on the type of coffee, they also dispense with the final cracking, which is known as French toasting.

After roasting, the coffee beans are around 20 per cent lighter than before the roasting process. They are now firm to the bite and need to be stored for some time before grinding.

The three methods of coffee roasting - roaster types
Coffee can be roasted using three different methods: traditional roasting, paddle roasting or fluidised bed roasting. In the classic drum roaster, the beans are placed in a rotating cylinder that is heated. In the paddle roaster, an internal paddle in the roasting chamber ensures that the beans are moved. In the fluidised bed roaster, or air roaster, there are no such parts for moving the beans. The beans are constantly suspended by a permanent flow of hot air.

Dark or light - the different degrees of roasting
Coffee is available in different degrees of roast. A distinction is generally made between three degrees of roast. The light, the medium and the dark roast. The very dark roast has been added in recent years. The differences are explained below.

Light roast
Light coffee roasts can be recognised by the light brown colour of the beans. They usually have a fruity and slightly acidic flavour. The lightly roasted bean contains more of the coffee's original flavours, which are determined by the region, the soil and the climate of the region of origin.

Medium roast
Medium-roasted coffee beans are slightly darker than the light roast. The acidity is lower and the flavours are nicely balanced. Medium-roast coffee is usually used for café crema, café au lait and espresso.

Dark roast
With the dark roast, the coffee bean is a dark brown colour. It appears oily and shiny. The bitter substances increase and the acidity is low. Dark-roasted beans are heated again to up to 210 degrees Celsius before the famous second crack. Dark-roasted coffee is characterised by a chocolaty taste with strong roasted aromas and traces of cloves and tobacco. Genuine Italian espresso is brewed from these blends, which can also be recognised by the very dark crema.

Very dark roast
Very dark roasted coffee has even stronger roasted flavours and aromas of tobacco and spices. The surface of the beans has lost its oiliness, they do not shine, but are a matt dark black colour. It is not yet so widespread, but is usually mixed with a dark roast in the cup of some espresso lovers.

The various roasts are packaged either pure or blended. The art of coffee roasting continues in the composition of different roast blends. The world of coffee is fascinating. Coffee roasters use their knowledge and skills to ensure that this world remains varied and offers the perfect beans for every coffee lover.