The Roasting Process
As coffee beans roast, several important chemical changes occur that affect the taste of the bean. Perhaps the most notable change is that the beans darken in color the longer they’re roasted. It is by this most obvious change that we classify each roast type. Let’s take a look at them in turn, considering the distinguishing features of each roast. Notice that the acidity level of the bean goes down during the roasting process, while the bitterness increases.
- Light Roast
- Color: Light Brown
- Sheen: Dry and dull, with no oil on the bean
- Flavor: Fruity and mild, with stronger acidity. Some feel like this roast has a grassy undeveloped taste. This roast has a strong aftertaste, that some prefer and other do not.
- Names: Cinnamon, Light Roast, Light City or Half City
- Medium Roast
- Color: Medium brown
- Sheen: Dry and dull, with no oil on the bean
- Flavor: Stronger, fuller flavor than the light roast beans. Less aciditic than the light roast with a strong aftertaste.
- Names: City, American, or Breakfast
- Medium-Dark Roast
- Color: Rich, darker chestnut brown
- Sheen: Some beans start to develop some oil (some don’t)
- Flavor: This roast style is considered by many to be the ultimate roast: the perfect balance point in terms of brightness, aroma, full body and varietal flavor characteristics. Coincidentally, this is the roast style most home roasters end up adopting as their favorite, especially those who initially liked the shiny, dark roasted beans they used to buy in the store.
- Names: Full City or Vienna
- Dark Roast
- Color: Dark brown to black
- Sheen: Somewhat shiny and oily to very shiny and oily
- Flavor: This roast style is not acidic but has a pronounced bitter taste. The smoky flavors of the roasting process are more pronounced.
- Names: Espresso, Italian, French, High, Viennese, or Continental
The process of roasting coffee beans is hundreds of years old. One legend tells of a weary mystic who was sustained and revitalized in the desert by coffee. When he returned home with the “miracle drink”, he was actually proclaimed a saint. While brewing a good cup of coffee may not always result in sainthood, there are rewards for the bold and persistent roaster. So, let’s roll up our sleeves. We’ve got some sacred work ahead of us!
Start Your Engines
Once we fire up our roaster, the beans will start to move. We’ll explain the process as if you can see the beans, even if you need to rely more on hearing and practiced timing to get your beans out at the proper moment. During this first part of the process the water in the beans starts to evaporate, and the chemical decomposition of the sugars (pyrolysis) is occurring. The beans get brighter, then turn yellowish and emit a wonderful smell.
There is, however, a special type of roasted coffee that's known as white coffee, which is roasted at lower temperatures than most coffee beans and for a longer period of time. The roasting process is stopped right before the first crack which results in a coffee bean that appears white, hence the name. The coffee bean itself is still hard and dense, so grinding it properly is of the utmost importance. This style of roasting results in a bean that has a pronounced acidity with a nutty flavor.
First Crack in the Roasting Process
Green coffee beans are full of water, and that water is getting ready to explode. As the heat level in the roaster rises, the water begins to turn to vapor. When that water vapor escapes, the beans expand, creating a cracking or popping sound. This “first crack” will sound like popcorn or breaking toothpicks and will be irregular in cadence. Beans will expand to roughly twice their green size but lose about 15% of their weight. At this point in time, the beans will begin to “float” in the roasting chamber and turn a light brown color. Stopping after first crack produces a light roast coffee bean. Because the sugar in the beans have not started to caramelize, light roasted beans do not have the same sweetness that you'll find in beans that go through the second crack.
- Cinnamon Roast - This is the lightest roast. The beans will be light brown and dry. Named for its cinnamon color when ground, this roast tastes somewhat grassy and slightly underdeveloped.
- City or American Roast - This roast is often called the American because Americans prefer this roast. The beans will be still be dry and dull but will have a darker brown than the cinnamon roast. This roast has a stronger and fruitier taste than the cinnamon roast.
People who prefer a medium-dark to dark roast need to really pay attention during the second crack in the roasting process. To many, this is where the magic happens, and it happens very quickly. The second crack starts slowly and is not as loud as the first crack. You’ll start to hear a soft staccato cracking sound almost like the sound of bacon sizzling. This is the sound of the actual cell walls in the beans breaking down and releasing carbon dioxide and oils. Little flecks of beans (called chaff) begin to break off the beans. It’s during this stage that the sugars in the coffee beans begin to caramelize, creating a sweeter flavor.
- Vienna/City Roast - The beans will have some oil on them and be chestnut brown. For many, this is the perfect stopping point.
- Espresso - The beans are dark brown and oily but not quite shiny for this roast.
- Italian to French - For these darkest roasts, the beans are oily and almost black. At this stage the sugars have stopped caramelizing and have started carbonizing which gives them a smokier taste.
- Charcoal - Kidding. This is not a roast, these are burned beans.
No one wants a gassy bean! You may not realize it, but this is the last stage in the roasting process. Beans need to cure in order to let all the extra gasses out and to develop a full flavor. This takes a minimum of four hours and up to twenty-four. Some swear that twelve hours is the perfect cure-time for flavor development. Regardless of your preference, it’s a good idea to give it those beans a rest.