Before we get into the specifics of the different roasting methods, let’s review some basic roasting concepts.
Depending on the roasting method you choose, the entire roasting process can take from between 10 and 30 minutes, though, it’s usually 15 to 20 minutes.
Probably the most important factor in the outcome of your roasting will be the type of green beans you choose. Coffees from different countries and growing regions have a wide range of characteristics. The best way to get to know the differences between various beans is to experiment with a variety of coffees and compare their flavors. Beyond this, practicing the art of blending different roasted coffees is another excellent way to familiarize yourself with coffee characteristics.
During the first half of the roasting process, the beans are essentially drying out. Green coffee has a moisture content of around 10%, although it can vary considerably based on ambient humidity, the origin, and age of the beans you’re using.
In the early stages of roasting, you may see some steam escaping from the beans and the coffee will have the smell of fresh grass. At this stage the beans are very dense and do not have much ‘coffee-like’ flavor yet.
Slowly, the beans will lose their green color and begin to turn a tannish/brown. You will also detect the smell of baking bread at this stage. The beans are on the verge of actually roasting rather than drying.
As the roast advances you will hear a crackling and popping sound. Once this sound begins, roasting has commenced. The popping sound (called the ‘first crack’) is the result of residual water inside the bean breaking free from carbon dioxide. This pinot makes the beginning of ‘pyrolysis’ where the beans begin to generate their own internal heat and smoke starts to emerge from the beans. Sugars inside the beans are caramelizing and the true coffee flavors are developing. It is at this stage that ‘chaff’ or the outer skin of the bean will separate and fly off the surface of the bean. The roast can be stopped anytime after pyrolysis has begun, depending on how dark you want your coffee.
The cracking noise will slowly subside and the beans will get darker and darker. After a short while a ‘second crack’ will begin to be heard which represents the breaking of the internal structure of the bean. Once this ‘second crack’ has started you have entered the category of ‘dark roast’. The smoke in this stage is more opaque and has a strong coffee smell.
The ‘peak’ of the second crack is about as far as you’ll want to go. Much beyond this will produce a thin, burnt tasting cup (though some people truly enjoy this charred taste). It is important to note that not all roasting methods can heat the beans to this point so some experimentation is necessary.
As you familiarize yourself with the roasting process, there are several ‘mileposts’ to watch for:
- The color and smell of the steam and smoke.
- The sound the coffee makes.
- The color of the beans.
Every bean will roast differently and the interaction of these ‘mileposts’ will tell you a lot about what is happening to the beans as they roast. As your techniques advance, you can begin to track the time and temperature of the roast by keeping a ‘roasting log’ that tracks the major variables of the roasting process.
The final stage of roasting is cooling the beans. Because the beans produce their own heat during the roast, it can take a couple of minutes to cool them down completely. The beans must be kept moving while cooling or they may heat themselves until they catch fire. This means you’ll want to cool the beans about a minute before they appear ready.