Coffee Basics: Acidity Differences

Learn how acidity differences in coffee occur based on the country of origin, processing method, and coffee bean roasting time.

Acidity is one of the four basic characteristics professional coffee tasters use to evaluate coffee. Body, flavor, and aroma are the other three. Together these four characteristics describe the sensory effects of a particular cup of coffee.

Acidity used in this way is a good thing. It is not sourness or bitterness. It is not what causes that unpleasant "acid stomach" feeling one can get from drinking some coffee. Rather, it is a pleasant taste sensation comparable to the one experienced when drinking dry red wine, a sensation that hits the palate as much as the tongue. Just as dry wines vary in their degree of dryness, coffees differ in their degree of acidity and in the quality of sensory experience the acidity produces.

While the amount of acidity in "good" coffee is a matter of style and individual taste, some acidity is desirable. Coffee without acidity is flat like soda without the fizz or food cooked without salt.

Coffee marketers and retailers often avoid the word acidity in their coffee descriptions in an attempt to avoid negative reactions. Instead they use words like tart, tangy, bright, lively, vibrant, crisp, sharp, and snappy to imply noticeable acidity. When the word acidity is used, it is usually qualified to indicate low, medium, or high acidity.

It is not completely understood how perceived acidity, the acidity recognized by tasters in a cup of brewed coffee, relates to the actual chemical makeup of coffee. From a chemical standpoint, coffee contains literally dozens of different kinds of acid compounds. How they interact with each other and how they interact with an individual's human body chemistry to produce the sensations coffee drinkers experience is not completely understood. It is known that the natural acidic character of a coffee when it is picked can be changed by processing and roasting techniques.

The variety of coffee plant, where the coffee is grown, how the beans are processed, how the beans are roasted, and how a brew is prepared all affect coffee acidity.

High-grown coffees, those grown at altitudes above about 4000 feet, and coffees grown in mineral-rich volcanic soils tend to be more acidic. You could therefore conclude that coffee grown in the highlands of Kenya would be more acidic than coffee grown at low elevations in Mexico. While it is tempting to generalize about acidity levels based on geography, acidity can be modified by processing and roasting. Thus it's not possible to be certain based on country of origin alone how much acidity a coffee will have once it hits the cup. Also, at the retail level, many coffees are blends. More expensive and more acidic highland coffee is often mixed with cheaper low-grown coffee before it reaches the consumer.

Coffee is processed using a traditional dry method, also known as the natural method, or using a wet method. Either method results in green coffee beans being extracted from the picked fruit of the coffee plant called cherries. With the dry method cherries are spread out in the sun to dry right after picking; the skin and pulp turn into a loose shell that is removed later. With the wet method the cherries are soaked right after harvesting to remove the skin and pulp before the beans are dried. Beans that are dry processed usually have less acidity than beans that are wet processed.

The same kind of bean processed using the same method can end up with acidity differences due to differences in roasting times. The longer a bean is roasted, the less acidity there will be. A darker roast, such as French or Italian, will have less acidity than lighter roasts such as those identified as Cinnamon, American, or Viennese.

Freshly brewed coffee made with filtered water will deliver the most acidity available in a particular batch of ground coffee. As the coffee sits and gets stale, it loses its acidity and the taste changes.

You can use this information to help you decide which coffee to try, but the best way to learn about acidity differences is to sample many different kinds of coffee.

© High Speed Ventures 2011