When coffee professionals talk about acidity, they do not mean the pH of your cup. They mean a quality of brightness and liveliness in the flavor, similar to the snap of a green apple or the zing of a lemon. Some coffees have a lot of it, some have very little, and the reasons span the entire production chain.
Origin and altitude
Higher altitude growing regions tend to produce more acidic coffees. The cooler temperatures slow cherry development, allowing more complex acid compounds to form in the bean. Coffees from Ethiopia, Kenya, and Colombia (often grown above 1,500 meters) tend to be brighter and more acidic than coffees from Brazil or Sumatra (often grown lower).
Processing method
Washed coffees emphasize acidity. Stripping away the fruit before drying lets the bean’s intrinsic compounds dominate. Natural and honey processed coffees, where the bean stays in contact with sugary fruit during drying, develop more body and sweetness, often masking some of the acidity.
Roast level
Lighter roasts preserve acidity. Darker roasts break down the acidic compounds during the longer roasting time, leaving a heavier, more bitter cup. If you want to taste acidity, drink lighter roasts. If you want to mute it, drink darker.
Brewing method
Pour-over and AeroPress with paper filters highlight acidity. French press and full-immersion methods produce a heavier-bodied cup that mutes acidity by comparison. Espresso concentrates everything, including acidity, but balances it with body.
Is acidity good or bad?
Neither, on its own. Bright, well-integrated acidity is one of the joys of specialty coffee. Sour, unpleasant acidity (often from underextraction) is a brewing problem to fix. The acidity of a Kenyan SL28 should taste like blackcurrant or grapefruit, not battery acid.