What does the roasting process do to coffee?

During the coffee roasting process, raw coffee undergoes a series of chemical and physical changes that transform them into the aromatic and flavorful beans we use to brew a cup of coffee. We’ve listed some of the most significant effects of the roasting process on coffee below:

Flavor development: roasting causes chemical reactions within a coffee bean that lead to the development of various flavors. During the roasting process, sugars and amino acids react to produce new compounds that contribute to a coffee's flavor profile. As the roast progresses, caramelization occurs, which produces a further range of compounds that can result in a wide range of flavors.

Fragrance and aroma development: the chemical changes that occur during roasting produce volatile compounds that are responsible for a coffee’s fragrance and aroma. These aromatic compounds are released when the roasted beans are ground and brewed, which produces the enticing aromas that we smell when preparing a cup of coffee.

Body, mouthfeel, and acidity: lighter roasts, like Schuil’s coffees from Ethiopia and Burundi, tend to have a lighter body and a higher acidity. Darker roasts, like Schuil’s Fogchaser and Seattle Blends, will have a fuller body and a heavier mouthfeel. The roasting process affects the oils within the beans, with lighter roasts retaining more of the natural oils, and darker roasts pushing oils to the surface, resulting in a shinier appearance.

Caffeine content: you can read in more detail about the always hot topic of the differences in caffeine content between light and dark roasts here. TLDR: the caffeine content in the bean remains the same during the roasting process, but differences in how coffees roasted at different levels extract when brewing do actually result in varying levels of caffeine that make it into the cup.