Roasting coffee is just cooking. You take an ingredient that's unpalatable — or downright inedible — and heat it to produce something delicious. And like cooking a delicious meal, roasting coffee is a surprisingly tricky process.
Learning just a little bit about it will help you understand how the coffee you enjoy was made. Armed with that knowledge you can select the best coffee for your palate.
Country of Origin
Each green bean picked has only potential flavor. Its actual flavor is gross. The spongy pale kernel of the coffee berry tastes almost nothing like the coffee it will become.
Each bean is a mixture of all the familiar food components: proteins, fats, carbohydrates. When you roast the beans, you begin a chain of chemical reactions among these constituents. The perfect roast brings all these reactions to a point where the flavors are balanced. That peak flavor in turn depends on the bean(s) and the unique growing conditions which produced them.
Taste is, well, a matter of taste. Some folks enjoy more bitterness. Some like sweeter, more complex flavors. On top of these preferences — and sometimes driving them — there's commerce: if you're a huge coffee producer, you need to make sure your product doesn't vary too much.
See, a Starbucks Pike Place Roast bought in Seattle needs to taste the same as one bought in Atlanta — or Bangkok. So you can't bring out the unique flavor of every bean; you need to find a repeatable recipe: a mix of origins, likely combined with a dark roast. Why a dark roast? We'll get to that.
So if you opt of easily-available coffee, you necessarily narrow the range of possible flavors you'll be drinking to those which work in a large-scale commercial operation.
Let's dive into the roasting process to see what other options there are.
Coffee roasters are huge cylinder of metal heated on the outside. The beans go in the hollow insides and the cylinder rotates. As it does, it heats the beans and because of the rotation, no one part of any bean gets scorched by lengthy contact with the cylinder, and no bean gets roasted any faster than any other.
The beans get dumped into the roaster and the beans are heated. Once the roaster decides the roast is done, the beans are dumped and cooled. Just how long and hot the roasting goes will determine the final flavor. You can thing of roasting as a timeline of flavor development; you chose the flavor profile by deciding when to stop.
Next, we'll take a look at that timeline in detail.
The first stage of roasting involves drying the beans. They contain a lot of water, so it takes a lot of time and heat to evaporate it all (well, most of it) out. Once most of the water is out, the beans will pop, just like popcorn. This is called 'first crack' and it marks the beginning of a time of rapid flavor changes in the coffee. You see, while there's a lot of water in the bean, you're basically just boiling them. Boiling as a cooking method is not known for it's flavor development. And as it is in the kitchen, so it goes in the roaster's drum. After the water is gone we can get into some very interesting flavors.
Between the Cracks
After first crack, the beans are light brown (called 'Cinnamon Roast') and dry on the outside. They proceed to darken until they eventually reach a dark brown color. At this point, there will be a 'second crack'.
At second crack, you've gotten the darkest of roasts and the beans are almost black, and oily on the outside. If you roast beyond second crack, you need to exercise care — you're moving inexorably to turning your fine beans from halfway across the world into very expensive charcoal.
The change in color is not the most interesting thing happening after first crack. Changes apparent to other senses are much more crucial: this is where the flavors are created.
Coffee beans have a certain amount of sugar in them. The roasting process first liberates them and then caramelizes them. Caramelization produces a more complex flavor, but one that's less sweet. So in general the darker the roast the less sweet it becomes, but the more caramel and complex, until finally all caramelized flavors are further transformed into decidedly not-sweet bitter flavors as the compounds begin to carbonize — literally turn ash.
The acidic taste in coffee is the dry, bright flavor. In general acidity will decrease as the roast progresses. Often coffees with a predominately acidic flavor will be described as fruity. The kind of fruit mentioned will give you an idea of the balance between the acidity and sweetness: a coffee with "notes of lemon" will be quite acidic and not very sweet. A coffee with plum and fig flavors will be both acidic and sweet.
Bitterness is one of the defining flavors in coffee. Bitterness generally increases as the coffee is roasted.
Ah, caffeine! Perhaps it'll surprise you to learn that caffeine content goes down the longer the coffee roasts. So that bitter, almost-burnt, brew that tastes as if it would wake a corpse actually has less caffeine than the more delicate-tasting lighter roast roasted from the same beans.
Take the roasting beyond second crack and you start to start to carbonize the beans. A little carbonization — like the black char on a steak — can be an interesting flavor. Too much of it and you start to feel like you're drinking charcoal.
One of the trickier aspects of roasting is that every bean goes the process at a different rate. Even with all the precautions taken in the design of the roasting machine to heat every bean evenly, beans vary in the moisture content, their size, and how close they end up to the heat source during roasting. Because of this, even very light roasts will contain a few carbonized beans. Diligent roasters (such as us, of course!) will take care to remove these since they're especially out of place in a lighter roast.
Putting this all together then, after first crack the coffee will progress from a bright 'clean', acidic flavor with substantial difference based on its origin to a less acidic, 'heavier', stronger and more bitter brew with fewer idiosyncrasies. This is described as a transition from the origin character to the roast character.
Post-Roasting Flavor Development
After the roast is done, flavor potential will continue to improve for a while, and then begin its long journey into staleness.
Next, the choice of [grinding][cremazen-grinding], brewing method will determine what aspects of the beans' flavor profile are emphasized.
Finally, the biggest change in the flavor of the coffee that actually passes your lips will be made after it brews: adding sugar, cream (or creamer), flavors, etc...
As we mentioned above, the darker roasts are more bitter and less sweet. Such roasts have a bold flavor which can stand up through these very strong companions. This is why large chains that sell lots of very sweet coffee drinks prefer darker roasts: you'll still be able to taste a coffee-like flavor even with 600 calories worth of sugar and milkfat.
Roasting at Cremazen
At Cremazen, we believe in customizing the roast to the bean in our single-origin coffees. Our aim is to bring out the best possible flavor from each batch so you can taste the terroir — the unique flavor that a particular spot on the earth infused into its plants. This means some trade-offs: the supply of the green beans is limited and seasonal. So our Burundi may come and go. The flavor of each single-origin is unique.
Our only blend — the [Festival Blend][festival-blend] — maintains consistency over time by using a mix of reliably-supplied single origin beans. Being more darkly roasted, it'll stand up better to cream and sugar, if you prefer your coffee that way.
- The more you add to your coffee — cream, sugar, flavor pumps — the darker a roast and the more you should chose blended rather than single-origin.
- If you take your coffee black, try single-origin, lighter roasts. If you haven't done so, you might discover an entirely different kind of coffee than you're used to.
- Pair your coffee with a suitable brewing method: darker roasts benefit from coarser grinds and longer brewing methods (e.g. French Press), lighter roasts benefit from finer grinds shorter brewing times (espresso and pour over)
Notes & Links
- What is the science behind coffee roasting? - Quora
- Sugars in roasted coffee - a conversation - jimseven
- Balancing act – Sweetness | Deaton
- How sweet is your cup? | Deaton
- Taste Notes + Flavor Notes | Coava Coffee Roasters
- CoffeeCuppers.com: Coffee Tasting Glossary
- How to Make Perfect Coffee - The Atlantic
- Coffee Roasts from Light to Dark - Coffee Crossroads
- Coffee roasting - Wikipedia, the free encyclopedia
- Coffee Roasting - CoffeeResearch.org
- Guatemalan Coffee
- Coffee Body
- Coffee Flavor