Blue Bottle Explains: Acidity

What does it mean when we say a coffee has acidity?


Dear Blue Bottle,

I’ve heard of coffees sometimes described as acidic. What does that mean? Is acidity in coffee a good thing?


Piqued Piquancy

If you’ve ever tasted a coffee and experienced a fresh brightness in your mouth—like biting into a green apple or sipping tart cherry juice—you’ve encountered acidity. As a roaster, I like the vibrant, “upper octave” notes that acidity adds to a blend, especially as it balances out a hefty body.

Most of us are accustomed to associating acidity with a certain flavor, but acidity can also be thought of more broadly as a sensation—also a type of mouthfeel—that different palates perceive in unique ways. It can range from delightful to downright distasteful.

Generally, while too much acidity makes the coffee taste sour, a balanced “brightness” (another word we use for acidity) adds dimension and clarity to the taste of the coffee.

How Regions Affect Acidity

Acidity is especially celebrated in single-origin coffees, where the brightness helps describe the coffee’s personality. Depending on the environment in which it is grown, coffee will naturally produce certain levels of acidity. In the right amount, acidity gives coffee a pleasing complexity.

We expect a coffee grown in Colombia, for example, to be more balanced in both body and acidity, with flavor notes of milk chocolate and citrus. A coffee from Kenya will be denser and may mimic the acidic characteristics of lime and grapefruit. It will taste more acidic than coffees from Central or South America, which have different environmental influences.

How Roast Methods Affect Acidity

Roasting also affects the level of acidity you perceive in coffee. As a roaster, this is where I have the most fun and the biggest challenges.

Although roasting won’t enhance the existing acidity in a coffee, a longer roast may “cook out” the perceived acids. It’s similar to toasting a beautiful slice of sourdough bread: The darker you toast it, the more its naturally tang will be masked.

If it’s a coffee we’re using for a certain blend, then the coffee will be roasted to match the way that blend currently tastes. Classic blends—like Hayes Valley EspressoGiant Steps, and Bella Donovan—have a characteristically heavy, syrupy body and lower acidity. Those coffees are roasted longer to increase the intensity of the caramelized sugar flavor.

On the other hand, a blend such as Mixtape Volume VI is lighter in body and has sprightly acidity. A coffee for Mixtape will be roasted more lightly—with intense heat for a shorter amount of time—to allow the acidity and sweetness to shine.

We roasters have more freedom when working with a single-origin offering, like Ethiopia Sidama Hunkute. In these cases, we roast the coffee in whatever way we feel best highlights the bean’s inherent beauty. This usually involves a shorter roast with more intense heat, or additional heat adjustments throughout the roast. As a result, our single-origin coffees taste more acidic, nuanced, and layered in the cup.

Determining Your Personal Threshold for Acidity

Each person’s palate is different and we all have different thresholds when it comes to acidity—not to mention temperature, sweetness, spiciness, and bitterness. And just to keep things interesting, those tastes also change as we get older. The world of coffee is an enchanting place for those who are curious and gutsy: You’re the boss in deciding what you enjoy.