Roasting coffee is a complicated process. It requires understanding the time and temperatures needed to extract the full flavour from the beans. Coffee beans are matured in the coffee cherries and then fermented and dried to be sold as unroasted coffee beans. These beans are green in colour and have beany and grassy aromas. They do not smell like coffee at all. The beans require roasting to develop their aromas. These consist of between 800 to 1,000 different compounds.
Each batch of beans is unique, and it is roaster’s task to extract the right aromas in the right combinations and right ratios. This is done by applying heat to the beans with a specific machine called a roaster.
Every roaster records the effects of his or her actions and decisions during the roasting process and their effects on the end-flavour of the coffee. This is called a Roast Profile.
The Roast Profile has the same purpose as a recipe in cooking. It ensures consistency in aroma and flavour. This is something that is very important for clients of commercial roasters. Roast profiles are developed over time. They are unique to the roaster, the coffee bean and the roasting machine. Good coffee roasters stand and fall by their ability to retrieve the best flavour from each bean. This process requires a mixture of creativity and science.
Ultimately roasting involves “reading the beans”. The roaster observes and responds to the changes in the beans caused by applying heat over time.
There are several key moments in the process that forms the backbone of how a batch of coffee is roasted.
Charge or Drop Temperature. This refers to the starting temperature of the roaster when the beans are loaded to start the roasting process.
Turning Point. This is the point of equilibrium between the temperature of the beans and the drum. The temperature of the roaster will drop immediately after loading the beans because the cold beans absorb the heat from the roaster. The Turning Point is reached the moment the coffee has absorbed enough heat that the temperature stops falling and begins to rise again.
Rate of Rise (RoR). This measures the speed with which the temperature inside the beans increase. This is the result of the increased heat from the burners inside the roaster. It is expressed as the number of degrees per minute-to-minute.
Timing of Colour Changes. This measures the time it takes for the beans to change colour, from green to yellow to bread and beyond.
Roast Development time
Time and Temperature of First Crack. Throughout the roast, the coffee beans are losing moisture, sugars are caramelizing, and a multitude of other reactions are taking place. Moisture and gas are released along the seam of the beans when they reach is certain temperature and this results in a popping or cracking sound. This is the First Crack. The time and temperature of the First Crack are recorded in the Roast Profile.
The time between First and Second Crack. This measures the time between the first and second crack in the beans.
Timing of First Crack to End Roast Time. This is called Roast Development Time. The coffee will develop most of its flavour during the Roast Development time. It represents a small window of opportunity during which the actions of the roaster will determine how much acidity and body the roasted coffee will have.
The longer the Roast Development Time, the more body but less acidity the coffee will have. This means that longer roasted coffee will have more chocolate and less fruity notes. The entire time in Roast Development lasts generally between 45 seconds to 2 minutes.
Once the roasting is done, the coffee beans are decanted from the roaster to stirred to speed up the cooling down process. When coffee is roasted gases – including carbon dioxide – form inside the bean. To brew the coffee immediately after it is roasted would have a negative effect on the taste and profile of the coffee. Therefore, the roasted beans have to stand to degas for a few days. Thereafter, it can be shipped, either as ground coffee as whole beans.
Local Coffee Roasters
Slow Town Coffee Roasters and Two Beards Coffee Roasters are two prominent local coffee roasters in Namibia and both are located in Swakopmund.
Slowtown Coffee Roasters is Namibia’s oldest and largest artesian coffee roasters. Their roastery is located in down-town Swakopmund and the company owns coffee shops in Swakopmund, Walvis Bay and Windhoek.
Two Beards Coffee Roasters specialises in single-origin Arabica coffees. Their roastery is located on the outskirts of Swakopmund in a complex that also hosts Stillhouse Atlantic and Namib Dunes Brewery. They have an in-house coffee shop Two Beards and a Saint that serves café-style meals.