There’s a lot going on in a cup of coffee. From the time it hits your tongue and explodes into notes of cherry and strawberry, to the way it mellows into a softer honey or pecan flavor, and how it leaves a milky, chocolate feel in your mouth after you’ve swallowed it, taking a sip of a good cup of coffee can be an immensely flavorful experience. What exactly makes drinking coffee such a wild ride, and where do all these flavors come from? Like with so many other things, it all comes down to a little chemistry.
Coffee plays host to a wide variety of different chemical compounds that each have a unique effect on the way a coffee tastes, and it’s the way these compounds interact with each other that ultimately create that final flavor that you experience when you take a sip.
Besides caffeine, the most often talked about the chemical in coffee are acids. Many coffee aficionados will even describe the taste of coffee by referencing its acidic content (“I really like the taste of very acidic coffee” for example). It’s no wonder because it’s the acids that often contribute to the most noticeable and punchiest flavors in coffee. Most of the fruity flavors found in coffee owe their existence to the presence of acids. Citric acid, for example, makes coffee taste especially bright, and gives it a taste akin to fruits like lemon, orange, or grapefruit, while malic acids create more apple-like flavors.
Coffee is nothing if not complex, though, and it’s not just the acids playing a part in creating the full flavor. Another key component in the makeup of coffee is lipids. Lipids help balance out the brightness of the acids by helping to create a creamy mouthfeel, often being associated with flavors like milk or dark chocolate. Paper filters can filter out a varying degree of these lipids, which is why some brew methods (like the Chemex) are described as creating a “clean” or “crisp” cup, removing the lipids and the oils that can muddy up a coffee if found in too high quantities.
Sugars are present in coffee as well but don’t contribute to as much of the sweetness as you might expect. The sugars often contribute much in the way of aroma (which certainly affects our perception of the flavors we taste), but a majority of what we might perceive as notes of honey, caramel, or other sweet flavors are actually the result of ketones (your body actually produces ketones in certain instances of malnutrition, which is why diabetics who are suffering insulin shock are said to have sweet or fruity smelling breath).
When all of these chemicals come together in the perfect balance, the result is smooth, complex, sweet cup of coffee that changes and develops in your mouth as you drink it, akin to the experience described at the beginning of this post. So next time you drink a great cup of coffee that really blows you away, don’t tell your barista what great brew skills they have. Compliment them on their chemistry.