Roasting Coffee Beans is essentially cooking green coffee beans. Except it's actually a lot more than that. Throwing beans in a pan doesn't really work, nor does baking them. The roasting process roasts the beans in a very controlled and precise way, and it's fascinating.
Let's explore together what roasting actually does to coffee beans, including ...
- Why we even roast coffee in the first place.
- How large toasters are better than another industrial kitchen equipment.
- What happens inside the bean at different stages?
- And how those stages affect the final taste.
This blog will give you an idea of how roasting here at Driven is a craft, not a factory production line. It will help you understand how flavors are formed and help you choose better beans the next time you are trying to decide between a few bags.
Lets start by the beginning.
Why do we have to roast coffee beans?
Coffee beans, as you know, are the seeds of a small cherry-like fruit. When first harvested and removed from cherries, they are hard, dense, and green in color.
If you were to try to prepare these green coffee beans as roasted coffee, the result would be unrecognizable and gross. Before roasting, the coffee beans have a very vegetal and "green" flavor. They are also so dense that most grinders couldn't break them into smaller pieces. Not very good for making coffee.
Roasting coffee beans breaks down the cell structures of the beans and extracts the moisture they contain to grind them. Roasting also initiates a series of complex chemical reactions that create the rich flavors we love in coffee, whether it's fruity and floral notes or deeper hues of chocolate and caramel.
Why We Use Large Coffee Roasters
Here's the thing: it is possible to roast coffee in a frying pan, over a fire or in the oven. In fact, it has been done that way for hundreds of years. However, these methods fall short in some dramatic ways, resulting in an unpleasant, unbalanced taste.
The greatest weakness of these methods is the lack of control. Roasting specialty coffee generally requires a specific temperature rise throughout the entire process. There is leeway for different techniques and styles, but on the micro level. Pans and ovens cannot allow this level of control or precision.
Another drawback of these methods is the fact that they cannot roast the beans evenly. The pans are hot, but the air around them is not. Baking distributes the heat a little more evenly, but you can't stir the beans without lowering the temperature. Unevenly roasted beans are not tasty beans.
Large commercial roasters continually chuck the beans to make sure they are evenly roasted. They also give us a very high degree of control over temperature. For delicious specialty coffee, they are the way to go.
5 main chemical reactions inside beans
There are thousands of chemical reactions that take place during coffee roasting, but we'll focus on the big five and how they develop the unique flavors of coffee.
During the first few minutes of roasting, the beans heat up, actually expand in size, turn a roasted yellow color, and begin to smell like toast or popcorn. And then comes the good stuff.
- Maillard Reactions: This is a large one that is responsible for a large part of the flavor of roasted coffee. Between 300- and 400-degrees Fahrenheit, a variety of chemical compounds, including amino acids in proteins, begin to react together to create more palatable flavor and aroma compounds. During this stage, hundreds of flavors develop in just minutes.
- Caramelization: Around 370 degrees, the natural sucrose (sugars) in the beans begins to caramelize. The aromatic and acidic compounds are released into the bean, and that sweetness changes from being like refined sugar to a deeper and more satisfying honey or caramel sweetness.
- First crack: just above 400 degrees, the remaining water in the bean vaporizes, causing the bean to expand and crack audibly. Beans lose about 5% of their weight due to loss of water and turn light brown in color. Shortly after the first crack is when the light roasts are removed from the roaster and cooled.
- Pyrolysis - Around 430 degrees, the beans undergo another chemical change that quickly expels the trapped carbon dioxide. The beans turn a darker brown color and lose about 13% of their weight due to the lost carbon dioxide. During this time, the bright acids from the caramelization soften from the deeper roast and more rounded flavors are formed.
- Second Crack: Just before 450 degrees, the grains experience a second audible crack, mainly due to pyrolysis that ejects carbon dioxide very quickly. Right after this point, the sugars and acids begin to break down into the darker, woody, carbonic flavors that are more common among dark roasts and the classic dark roast coffee aroma develops fully.
The old way of roasting coffee used to bring the beans to the second crack, but that's less so among specialty coffee roasters. Most beans reach a better stage of balance, sweetness, and flavor between the first and second cracks (around a medium roast).
And those super dark, oily beans that taste like ash and bitterness? Those are roasted past the second crack stage. We never roast coffee this far; generally, destroys all good and interesting flavors.
We just bring out the best and most satisfying flavors we can when we grill. Sometimes it is a light or medium roast, but we also have a couple of darker options.
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