Coffee Roasting

Roasting Basics

Taking a grey-ish, green seed and turning it into a beautifully browned seed with which one can take, grind and brew a delicious cup of coffee is a challenging task that many of us take for granted. Behind each bag of roasted coffee was (hopefully) a well-thought and executed plan to bring out the best in that particular coffee. Just like a chef of a Michelin star restaurant or a professional baker. A roaster has to carefully manage each stage of a roast to ensure that the coffee doesn’t burn or isn’t underdone. A good metaphor to compare it to is a steak. When ordering a steak there are different degrees to which people want their steaks cooked. So a chef must carefully cook the steak to the right temperature. This is a perfect analogy for roast level in coffee roasting. You may like a dark roast (the coffee equivalent of a well-done steak), but for me I prefer a coffee that’s medium-light to light (the coffee equivalent of a medium-rare or slightly rare steak). 

Now that you have that analogy in mind for roast level. I’d like to mention quickly about how it’s much more than just heating the beans up to be until they are the right color. There are 3 stages that coffee goes through that a roaster must watch. (And many times they must make adjustments while they monitor the process.) The first stage is the drying phase. During the drying phase the coffee is doing just that—drying. Green coffee actually comes to the roaster with a residual moisture content of anywhere between 11-13%. During the drying phase this is being cooked away. Next, we arrive at the yellowing/Maillard phase. During this stage the coffee turns yellow. (These phases are pretty aptly named, right? 😂 Also occurring during this phase is the maillard reaction that is why it’s also called the maillard phase. This reaction is what makes roasted coffee, seared steak, toasted break, and baked cookies smell and taste amazing. When heat is applied the sugars and amino acids (proteins) in the coffee react together. This creates hundreds of new flavor and aroma compounds. Also, around this time or shortly after the maillard phase the coffee will reach first crack. This is when an audible crack can be heard by the roaster. This happens because the heat causes the water inside the bean to create steam and it also causes gases like CO2 to build up and create pressure. The crack happens when it becomes too much for the little bean to handle anymore. First crack usually marks the beginning of the development phase. During this last phase–the development phase–the coffee really starts to develop its flavors. Aromatic compounds form, acidity softens, and sweetness increases as remaining sugars in the coffee break down. There are lots of chemical reactions that are taking place and things like where the coffee was grown, how it was processed, and how the roaster changes variables like heat and time will all affect how the coffee will develop its full flavor during this phase. After this the coffee is dropped and hot air is pulled away to try and cool it as fast as possible because, again like steaks, it continues to cook after it’s pulled off of the heat. 

How long this process takes depends on the specific type of roaster that you use, but generally speaking almost all roast fall between 5-15 mins. So, relatively speaking, this is a very fast and sensitive process, but when it’s done well the results are (in my opinion) the best thing that a person can drink.