Why Roast Coffee? What Happens When Green Beans Meet Heat
A beginner's look at the science behind your morning cup
Roasting coffee is essential to flavor development. Serving coffee in its green bean state would be incredibly astringent, sour, and grassy — not really something you’d enjoy in your morning cup. The roasting process actually unlocks the complex flavors we enjoy: the body, the sweetness, the aromas. Without roasting, we wouldn’t experience this flavor complexity at all. Not only that, it would be nearly impossible to get a good grind with green beans.
Last week, I had the pleasure of attending the second installment of my coffee roasting school. We selected beans from three different origins, roasted them to the same profile, and got incredibly different results. Same temperature, same time — completely different cups. It was one of those moments that cemented how much origin really matters, even when every other variable is under your control. I wrote a post on single origin coffee and terroir if you want to learn more!
Coffee roasting is a combination of two things: temperature and time. How hot (or how cool) and for how long. A lighter roast preserves more of the bean’s original character, bringing out its brightness and acidity. A darker roast brings out deeper, bolder flavors like chocolate and caramel while toning down the brightness. The job of a roaster is to decide where on that spectrum each coffee belongs, and that may look very different to every roaster.
There are different methods of roasting coffee but the most common one is drum roasting where beans tumble in a heated rotating drum. It’s the traditional method and preferred by many because of the amount of control it gives you over the process. This is also the one we used in our course and I thoroughly enjoyed it. There are others like air roasting (also called fluid bed) where hot air lifts and circulates the beans to roast them more evenly and quickly. Each method offers different benefits and it’s one another variable that shapes what ends up in your cup.
This is one of the reasons I decided to learn to roast myself. I want to understand what’s happening inside the drum so that when I eventually start roasting my own coffee, every batch is made with intentionality.
What’s your favorite roast profile and why? Let me know in the comments below!
Your class sounds really fun, Bernardette! And I hope you all get to sit down at the end with a nice hot cup of java!!
How fun, to be taking a roasting class in something we love to drink yet often don't think about what goes into a coffee we love vs one we never buy again. Ahhh the scent!