Maybe it’s bright, juicy, or sour — or perhaps it has the tang of a lemon, or the sparkling sensation of a key lime. If you're a coffee drinker, you may be curious to learn more about how the roasting process can affect your coffee's acidity. Acidity in coffee is the fresh fruit character that stands out in the cup. At its best, it’s bright, crisp, and juicy, and at its worst it’s sour, sharp, and unbalanced.
Is acidity a sensation or a flavor?
According to coffeeresearch.org, acidity is the bright and dry taste that adds life to coffee. Acidity lends this function in coffee, adding dimension and taking on the characteristics of flavors in the cup. Coffee isn’t inherently overly acidic, in fact the pH is actually 4.5 to 6, just like a banana, which rates pretty low on the pH scale.
Sourness is one of the five basic taste sensations that we can perceive on our palate (along with sweet, bitter, salty, and umami). We actually perceive flavor through the combination of taste and aroma, which is why acidity is often a combination of both a sensation and a flavor.
A great way to get your palate used to perceiving and describing acidity is to taste different types of fruit side by side, noting where your tongue lights up. A lemon-like acidity will differ greatly from the surprisingly sour blood orange, for example. A coffee may not taste like the exact fruit, but instead the way the coffee expresses acidity will be like that of the fruit. Not only is this a great exercise in perceiving coffee and acidity, it’s a tool to start building your own personal flavor memory bank.
Organic acids are present in both unroasted and roasted coffees, and are generally positive qualities to have.
The degree of organic acids present in regular coffee will have to do with terroir, variety, and processing methods. For instance, coffee grown at a higher altitude in a cooler environment will have a higher degree of acidity and a coffee grown at a low altitude in a warmer climate will have low acidity. An extreme example is a 2,000 meters above sea level (masl) grown Kenyan coffee that has been planted in volcanic soil will have a higher concentration of organic acids than a Brazilian coffee that has been grown at an average of 1100 masl without volcanic soil.
Due to this, certain varieties and cultivars will have different concentrations of organic acids depending on where they’re naturally from. Processing method affects this additionally. A washed processed coffee will have a clearer articulation of flavor and therefore perceived acidity, whereas a dry processed coffee will have low acidity.
Citric acid: Citric acid is the most commonly found acid in coffee, and is also found primarily in citrus fruits. Lemons, limes, oranges, grapefruits, and raspberries are all high in citric acid.
Malic acid: Is your cup as smooth and crisp as a green apple, or does it have the juiciness of a ripe pear? You guessed it, malic acid is the kind of acid most commonly found in apples, pears, and many other fruits.
Tartaric acid: Primarily found in grapes, tartaric acid is a dry acidity that can also be located in tamarind, cherry, and bananas.
Phosphoric acid: A slightly sweeter acidity with a sparkling quality, this type of acidity is responsible for that tangy quality in a Kenyan coffee or a sparkling soda.
Acetic acid: On it’s own, it’s vinegary, but in a natural coffee, acetic acid can be quite pleasant.
Roasting and acidity
During the roasting process, chlorogenic acids are broken down into caffeic and quinic acids, increasing the bitterness of the resulting cup.
Additionally, as the roast progresses, more sugars develop as coffee's acidity breaks down. A lighter roasted coffee, for example, will have a clearer and more vibrant acidity than a dark roast.
Manipulating coffee acidity
Although there are natural acids present in coffee no matter what, you can manipulate your process of brewing coffee to increase or decrease the presence of acidity in your cup.
You can slow down the brewing process with a finer grind to bring out more sugars. If you’re drinking coffee and find your brew to be flat tasting, you can speed up the brewing process with a coarser grind for more acidic coffee.
Organic acids are extracted first when brewing coffee, followed by sugars. If you find your cup to be overwhelmingly acidic, you can slow down the brewing process with a finer grind to bring out more sugars for reduced acidity. If you find your brew to taste flat, you can speed up the brewing process with a coarser grind to help make that coffee acidity pop.
Coffee recommendations that showcase acidity
For a coffee with malic acid
Madcap’s Luis Reinoso has a crisp and clean green apple acidity that mingles with grapefruit and nougat for a deeply satisfying cup.
For a coffee with citric acid
Huckleberry’s Kenya Gondo Peaberry is bursting with a mouthwatering raspberry and lime acidity that reminds us of the perfect blend of raspberry tea and limeade.
For a coffee with tartaric acid
Irving Farm’s Gakenke Burundi has a bright cherry acidity with baking spice and dark brown sugar that reminds us of our favorite cherry pie
For a coffee with acetic acid
Methodical’s Honduras Finca la Unica is a naturally processed, funky-fruity delight. Loaded with chocolaty sweetness and a banana-like acidity with strawberries and cream, peach cobbler, and a hot fudge sundae.