What is Acidity in Coffee?
What Does Acidity in Coffee Mean?
Acidity is a term commonly used to describe coffee, and it is viewed in a positive light. What does acidity mean in coffee? Acidity is used to describe the various aromas perceived in coffee that can be directly attributed to the acids naturally present in the coffee beans.
Roasting Alters the Acids in Coffee
Before looking at the specific acids found in coffee, let’s refresh some basic knowledge. Simply put, an acid is a substance with a pH value lower than 7 — meaning it donates H⁺ ions in an aqueous solution. When we taste an acid, the released H⁺ ions stimulate neurons on the tongue, sending signals to the brain that we associate with different flavors. The specific flavors we identify from an acid depend on its precise chemical structure.
As green coffee beans undergo chemical reactions during roasting, the concentrations of certain acids change. Most acids decrease at higher temperatures, though some increase. In general, roasting aims to bring out the best balance of naturally occurring acids in a particular coffee, as these compounds are what give coffee its unique character.
Acids Found in Coffee and Their Characteristics
There are a number of different acids found in coffee. In this overview, we’ll focus on those that remain after the roasting process, as they are the ones that influence the final flavor of the coffee. Some of the acids listed below have a positive effect on coffee, while others can have both positive and negative effects.
Citric acid is found in Arabica beans grown at higher elevations. This acid is the same as the one found in citrus fruits. When combined with malic and phosphoric acids, it can create grapefruit-like notes.
Phosphoric acid is sweeter than most acids. It can transform a tart citrus flavor into something closer to sweet grapefruit or mango.
Malic acid sometimes appears in stone fruits like peaches or plums, but in coffees with malic acid, apple or pear notes are more commonly perceived.
Chlorogenic acids (CGAs) are largely responsible for a coffee’s perceived acidity. They break down rapidly during roasting, which is why light roasts are often described as “bright” and “acidic,” while darker roasts are less so.
Acetic acid, the same acid found in vinegar, can create a pleasant clarity at low concentrations but tastes unpleasant at higher levels.
Tartaric acid, similarly, produces sour flavors at high concentrations, but at lower levels it contributes grape-like or winey notes — unsurprising since tartaric acid is found in grapes.
Quinic acid is produced as other acids degrade. It is commonly found in dark-roasted coffee, stale coffee, or coffee that has been sitting for hours on a hot plate. While it can add a clean finish, quinic acid is the main cause of sourness in the stomach.
Many of the flavors you identify in coffee can be directly traced to the acids it contains. If you can pinpoint which acids you prefer, you can start seeking out coffees grown or roasted in ways that emphasize those particular acids. Perhaps by looking more closely at chemical reactions and their impact on coffee, we can make exciting new discoveries.