Acidity in Coffee

Why It Matters

One of the most prized attributes and one of the most misunderstood, acidity adds dimension to coffee. At Blue Bottle, we often think of acidity as the upper octave notes in a coffee or the bright light shining through on a dark night. To a certain extent, acidity is inherent to a coffee but the way it’s perceived can be changed by the way it’s roasted and the way it’s brewed. Read on to learn more. 

IS ACIDITY IN COFFEE GOOD OR BAD? 

Sometimes our guests get scared off when we talk about acidity. “I think one of the big issues with acidity in coffee is the word itself,” says Kevin Thaxton, Senior Quality & Innovation Manager for Asia. “Acidity does not sound delicious or like something you should be consuming.” 

When we taste coffee, we often use words like “bright” or “snappy” or “lively” or “zingy” to describe its pleasing acidity. We also discuss acidity by citing specific flavors as well as the mouthfeel. Does this coffee remind us of biting into a green apple or sipping tart cherry juice? Does it make your mouth pucker?

Acidity is just one of the flavor elements of coffee, so on its own, it’s neither good or bad. At Blue Bottle, we’re always looking at how the acidity is integrated into the coffee. Does it taste in balance with the body, sweetness, and other flavors or is it unpleasantly sour? Does it have so little acidity that the coffee just tastes flat?

Of course, there’s also personal preference. “What tastes good to me might not taste good to you,” says Pele Aveau, Learning and Development Program Manager. “Plus, there’s also your mood. I’m not always in the mood for a coffee with lots of fruit flavors and high natural acids. Sometimes, I want something sweeter and rounder.” 

HOW COFFEE TERROIR AFFECTS ACIDITY

In the wine world, people use the word “terroir” to describe all the intricacies about where the grapes grow and how that affects the final wine. This concept is also true in coffee, which comes from the seed of a tropical fruit. 

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. Coffee varieties, climate, elevation, and processing can also impact the amount of acidity a coffee has. For example, higher-elevation coffee matures at a slower rate due to the cooler temperatures and less oxygen, which results in coffees with complex flavors, higher acidity, and higher levels of sugars.

For example, we expect a coffee grown in Brazil, often grown at lower elevation, to be fuller bodied and rich with chocolate notes and mellow acidity. A coffee from Kenya, grown at higher elevations, is often lighter but vibrant with an acidity that can mimic lime and grapefruit. 

Like wine, coffee can have such a wide expression of flavors from the darker bittersweet flavors, to bright fruity complex flavors and that range is something that can lead to endless exploration.

HOW ROASTING AFFECTS COFFEE’S ACIDITY

Roasting also affects the level of acidity you perceive in coffee. Although roasting won’t enhance the existing acidity in a coffee, a longer roast may flatten the flavors of the perceived acids. It’s similar to toasting a beautiful slice of sourdough bread: the darker you toast it, the more its natural tang will be masked.

“By using less heat energy and drawing out the roast longer, the acidity can be softened up, becoming less ‘peaked’ and can be perceived as rounder,” Kevin says. “By continuing to push the roast in duration and to higher temperatures, you move into more of the chocolaty flavors and the acidity can be quite muted at this point.” 

For example, our classic blends—like Hayes Valley Espresso, Giant 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.

For our single origin coffees, especially those from East Africa that can have higher levels of acidity, we roast them in a way to highlight these attributes. “If you stop the roast too early, the coffee can be sour, grassy, and the flavors not fully realized,” says Kevin. “Ending the roast too late can result in the sparkling acidity to go dim. There is a small window though, and if you catch it just right, the coffee is unlocked with complex fruity flavors, a pristine acidity and dimension.”

HOW DOES ACIDITY CHANGE WHEN BREWING COFFEE?

When brewing coffee, you want to extract it properly so you taste the acidity as an integrated part of a whole. When a coffee is underextracted, which can happen when you use too much water to the amount of coffee you have, your water is too cold, or your grind is too coarse so the water slides through too quickly, you can have a coffee with out-of-balance sour flavors. 

“When you think about solubility in coffee, the first thing to wash off the coffee are those salty, acidic flavors,” says Pele. In an underextracted coffee, the coffee’s natural sweetness is still locked inside the beans. 

So how do you know when you’re dealing with underextraction versus a coffee that just has high acidity? 

“To me, the difference between a coffee that has pleasing acidity and one that’s underextracted is the presence of vegetal flavors,” says Mariana Mandelbaum, Creative Project Coordinator. “When a coffee is sour from underextraction, it pulls at the sides of my tongue and cheeks, like I’m sucking on a Warheads candy. When it’s in balance, acidity tastes vibrant and sparkling.” 

WHAT KINDS OF ACIDS MIGHT YOU FIND WHEN TASTING COFFEE?

There are many different types of acids we find in coffee, but some of the easiest to identify are those that mimic foods we already know. 

“So if a coffee has that sharpness when you first bite into a green apple, it’s likely malic acid. If the coffee gives your tongue a sparkling sensation, almost like Coca-Cola, it’s probably phosphoric acid. And citric acid is like biting into a lemon,” says Mariana. 

While you don’t necessarily need to know what types of acids are in your coffee, being able to identify those types of flavors can help get you closer to finding coffees you love. 

WHAT SHOULD I ASK FOR IF I LIKE LOW-ACID COFFEES?

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. 

If you’re at a cafe, never be afraid to ask the barista for their recommendation. They know the menu well and can guide you toward a coffee you will love. 

If you’re shopping for coffee in a store or online, there are a few generalities to know: “A medium to dark roast can be a fairly safe bet if you are searching for a lower-acid coffee,” says Kevin. Also, coffees from Brazil, Mexico, or Sumatra tend to be rich and full bodied with lower acidity. 

If you’re open to trying coffees that are more fruity than chocolaty but aren’t overwhelmingly acidic, you might try a natural-process coffee, meaning the seed is dried with the fruit intact. 

“While known for their fruity winey flavors, the acidity tastes rounded instead of sharp because the coffee has so much natural sweetness,” says Kevin.

To get to know the style of coffee you like best, start with our Blend Box, which includes our mellow, chocolaty Giant Steps; cozy, raspberry-inflected Bella Donovan; and our brighter Three Africas.