I often have people ask me for coffee recommendations and they tend to say one of two things, either “I like dark roasts” or “I like coffee that doesn’t have acidity”. As a roaster, I find this really interesting because the current trend of “Third Wave” coffee is all about emphasizing the uniqueness of coffee origins by roasting light and highlighting the characteristic acidity in coffee.
Let’s get one thing straight. All coffee is acidic, to some degree. There are around 50 different acids that occur within a coffee bean, either when growing and harvested, or created during roasting. Some of those acids are important to the flavor of the coffee. Acidity adds brightness to the flavor, and gives the characteristic “fruit notes” that some will identify in a given coffee. Other acids produce undesirable flavors, like sourness or bitterness.
The primary acids in a coffee include chlorogenic acid, citric acid, malic acid, acetic acid, quinic acid, and cafetic acid. Each of these acids contribute to the taste of coffee, and each can be manipulated through the application of heat during roasting. Citric acid can come through as lemon, lime, orange, or grapefruit. Malic acid brings with it notes of apple peel or pear. Acetic acid can highlight lime notes, or can make a coffee taste sour if too high in concentration.
When someone says they don’t like a coffee that is too acidic, they’re usually talking about quinic acid. This is the one that creates the “sour stomach” that some coffee drinkers experience. While dark roasted coffees are higher in quinic acid, it’s really stale coffee or coffee that has been sitting on a hot plate too long that has the highest concentrations of quinic acid. If you want to avoid sour stomach, drink fresh roasted coffee.
The contradiction I run into is when someone says “I like dark roasts that have low acidity because the acid bothers my stomach”. As you roast darker, you increase quinic acid, which is what bothers the stomach. And if you roast slower, you decrease the level of chlorogenic acid, which gives coffee its perception of acidity. This is a conundrum, and it leads me to ask more questions because I need to know whether it is a flavor profile they do not like, or a physical feeling of sour, jittery stomach that they don’t wish to experience.
A slow roast, that is also a medium roast level, will have the lower perception of acidity and the lower level of quinic acid, and this is what I often do to create pleasing coffees that won’t win awards, but is a hit with customers. For those rare occasions when I want to knock one out of the ballpark, I like to take a high grown coffee and roast it fast, to preserve much of the brightness and fruit notes. It always amazes me when I taste citrus fruit in my coffee, knowing that it’s a flavor that was hiding in the bean the entire time.