Roasting coffee - the magic happens
Coffee roasters use conductive and convective heat to heat coffee beans. In our Probat UG22, the direct flame under the drum heats the drum which in turn heats the air inside the drum. This rather boring, and we’d like to say there is magic going on inside there (which there is) but the magic all starts with heat transfer and ends... well, who knows, that’s the magic part.
The beans inside the roaster have to be tossed around to ensure they are not in contact with the drum for any extended period of time. This can cause burning of the beans called tipping and scorching in roasting.
Most of the heat transfer in roasting comes from convective heat transfer from the air inside the hot drum, whereas a small amount comes from conductive transfer from the drum and other beans. This is why it is important to have the correct airflow settings within the roaster to allow for maximum convective heat transfer to the beans.
So that’s the dry scientific things that are happening inside the roaster, but where is this artistry people talk of in roasting coffee?
This comes in the manipulation of convective and conductive heat to turn those flavorless green beans into those delicious sweet, floral, rich, chocolaty notes you find in every cup of our coffees at 19 grams. You can roast a coffee to the exact same time and temperature and depending on how you get there, the results will be wildly different.
We have developed a style of roasting over years of trial and error that we believe brings out all the best qualities in the bean, without adding any harsh acidity or roasty notes, and that is where the magic lies.
Maillard reaction defined
In a nutshell, it's the process of combining the natural sugars with amino acids (protein components) to form melanoidins. They're what give roasted coffee it's brown color and contribute to the body of the coffee.
Maillard reactions are sugar browning reactions and produce flavours in coffee that are caramelly chocolaty and malty. Longer reaction times tends will achieve more complex flavours whereas shorter reaction times will leave brighter and more fruity notes, and we have to remember we are breaking down sugars with the Millard reaction, so the more complex and rich flavours will come at a cost. To put it more simply, it’s a balancing act of what you are trying to achieve.
How a bean gets brown and why a bean needs to get brown
The Maillard reaction is responsible for creating hundreds of aroma and flavor compounds in roasted coffee and by manipulating the roast we can change the flavour of the coffee we produce.
This is the same reaction that is happening when you are roasting a chicken, browning a steak or cooking down sugar.
In all these cases, eventually too much of a good thing will lead to burnt destroyed flavours and the goal is to achieve a balance. In Coffee, the Maillard reaction begins at around 150°C when you notice that the green beans have started to change in colour from green to yellow and then yellow to brown. Later in the roast they will become self-sustaining. We can adjust the application of heat to slow down or speed up this reaction and this is just one of the many ways we can influence the final cup you are drinking.
Experience our freshly roasted coffee here