Have you ever wondered why all the coffee you drink is roasted? The whole idea seems a little odd, if you think about it. Why would you cook the beans, if you plan on boiling them anyways? But roasting is an important part of what makes coffee taste like coffee.
Much like food, coffee tastes different after cooking than it did before. The reason comes down to what are known as “maillard reactions.” Maillard reactions are when an an amino acid and a special type of sugar change the other.
When heat is added, the sugar and the amino acid combine together to create a wide variety of different compounds. If even more heat is provided, then these compounds can be brokend down into even more different, but simpler compounds. It are these compounds that are responsible for the smell and flavor of the food you eat as well as the coffee you drink.]
It is the breaking down of the compounds from more complex to simpler that gives each individual roast its flavor. Light roasts leave more of the complex compounds intact, while darker roasts almost completely destroy them and leave only simple molecules.
Because of this, lighter roasts like half city and full city carry the flavor of the soil they were grown in much more readily than darker roasts. The flavors are also usually more complex, the acidicy higher, and the mouth feel lighter. Most commercial roasters stop at half city(one of the lightest) while most specialty roasters go to half city(which trades some complexity for reduced acidity). Darker roasts are less complex, but are generally less acidic. Usually they are heavier in the mouth and have a strong, intense flavor.
Full roasts still contain a hint of their origin soil, but it is hard to identify behind the intensity of the coffee. French roasting completely destroys the taste of the origin soil and removes most of the complexity of the bean’s flavor. But what you get in exchange is an extremely strong flavor and a smoky-sweetness.
Each person has their own preferred roast level. If you have never tried experimenting with different levels of roasting, I would highly recommend it. It is getting to be more common that you can find a variety of roasts in places as common as your supermarket.
But if you want ultimate control over your roast, you will need to roast your own beans. But that is another post.
Until next time keep your coffee hot!