Coffee Acidity: What It Means, pH and Low-Acid Coffee

Coffee acidity means two different things, and mixing them up causes a lot of confusion. To a taster, acidity is a quality: the bright, lively, sometimes fruity sensation that makes a coffee taste fresh rather than flat. To a chemist, it is a measurement, either pH or the total amount of acid in the brew. And to many shoppers, "acidic" is a warning about heartburn. This guide explains each meaning, what published research says about the acids in coffee, how roast level and brewing change them, and what "low-acid coffee" claims do and do not tell you. It is general information, not medical advice.

Acidity as a taste

When cuppers score a coffee, acidity is one of the attributes they judge (see how to cup coffee). Pleasant acidity is described as bright, crisp, juicy or winey, and is often compared to citrus, apple or berries; harsh acidity reads as sour. A coffee with very little acidity tastes flat or heavy, which some people enjoy and others find dull. Acidity in this sense is a matter of balance rather than amount: a mild coffee such as Jamaica Blue Mountain is usually described as having gentle acidity that sits in balance with its sweetness and body (see what Blue Mountain coffee tastes like).

Which acids are in coffee?

Brewed coffee contains a mix of organic acids. A 2023 study in Current Research in Food Science by Rune and colleagues measured citric, malic, chlorogenic, quinic, acetic, lactic, phosphoric, glycolic and formic acids in brewed coffees. Chlorogenic acids are the most abundant group; in Rao and Fuller's 2018 Scientific Reports study, one form (5-CQA) was the most plentiful in every sample.

The 2023 study also tested which acids people can actually taste. Only citric acid was clearly detectable at the concentrations found in coffee; malic, acetic and lactic acids were below their taste thresholds, and phosphoric acid was just below. When the researchers added extra acids to brewed coffee, thirteen coffee experts could not identify any of the five acids added. The authors concluded that perceived acidity seems to be a holistic property of the cup rather than the effect of any single acid, so a tasting note such as "malic, like green apple" is a description, not a chemical analysis.

Acidity in the lab: pH and titratable acidity

Chemists use two measures. pH tells you how acidic a liquid is at a given moment; lower is more acidic. Titratable acidity measures the total amount of acid that can be neutralized, which includes acids that are not affecting pH at that moment. In Rao and Fuller's 2018 study of six coffees, pH ranged from about 4.85 to 5.13, which is mildly acidic, and the authors found little correlation between pH and titratable acidity. In other words, two coffees with the same pH can contain quite different amounts of acid, which is one reason pH alone says little about how a coffee will taste.

How roast level changes acidity

Roasting changes the acid mix. Rune and colleagues found that as roasts got darker, citric, malic and chlorogenic acids fell, while quinic, acetic, lactic, phosphoric and glycolic acids rose; the total amount of organic acids stayed roughly constant, and pH rose with darker roasts. Because citric acid, the one acid people could clearly taste, declines with roasting, darker roasts generally taste less bright. That matches the long-standing description in Wikipedia's coffee roasting summary, where acidity is sharpest in light roasts and falls steadily as roasting continues (see coffee roast levels).

Does brewing method change acidity?

Cold brew is often sold as "less acidic". Rao and Fuller compared cold brew (7 hours at room temperature) with hot brew (6 minutes in boiling water) made from the same six light-to-medium roast coffees at the same ratio. The pH values were comparable, 4.96 to 5.13 for cold brew and 4.85 to 5.10 for hot brew, but the hot brews had higher titratable acidity for every coffee, as well as more chlorogenic acids and higher antioxidant activity. So cold brew does contain less total acid in that study, but it is not meaningfully less acidic by pH. The study measured chemistry only, not digestive symptoms.

Grind, time and temperature matter for hot coffee too. Under-extracted coffee, from a grind that is too coarse or a brew that is too short, tends to taste sour; over-extracted coffee tastes bitter. If a coffee tastes unpleasantly sharp, the brewing may be the problem rather than the beans (see the coffee grind size chart).

Origin, altitude and processing

Origin and processing shape a coffee's acidity as well. High-grown coffees develop more slowly and are often prized for brightness, which is why altitude grades such as SHB are used as a quality signal (see coffee altitude grades). Washed coffees are usually described as cleaner and brighter than naturals, whose fruit sweetness and body can soften the impression of acidity (see washed coffee and natural process coffee). Arabica is generally described as more acidic in the cup than robusta, which is lower in acidity and more bitter (see robusta coffee). The Rune study found little systematic difference in acids by country, with citric acid the main exception, though it tested only two samples per country.

Is coffee bad for acid reflux? What "low-acid coffee" means

"Low-acid" is a marketing term, not a regulated definition, so a label claim tells you little on its own. The evidence linking coffee's acidity to heartburn is also weaker than many people assume. Rao and Fuller cite earlier work by Thomas and colleagues that found reduced pressure in the lower esophageal sphincter at both pH 4.5 and pH 7.0, which suggests acidity may not be the main trigger.

Roast may matter for another reason. A 2014 study by Rubach and colleagues in Molecular Nutrition and Food Research gave nine healthy volunteers either a medium roast market blend or a dark roast blend. The dark roast contained much more N-methylpyridinium (87 versus 29 mg/L), a compound formed during roasting, and less chlorogenic acid, and it stimulated less stomach acid secretion. The authors called for further studies before drawing firm conclusions, and nine people is a very small sample. If coffee bothers your stomach, a darker roast, a cold brew or a smaller cup may be worth trying, but talk to a doctor about persistent symptoms.

How to find the acidity you like

1. Choose the roast first. Light roasts keep more bright acids; medium roasts balance acidity and sweetness; dark roasts taste least acidic.
2. Look at origin and process. High-grown washed arabica is usually brighter; naturals and many low-grown coffees taste softer and heavier.
3. Brew it correctly. A sour cup is often under-extracted, so try a slightly finer grind or a longer brew before blaming the beans.
4. Try milk or cold brew. Milk softens the impression of acidity, and cold brew had less total acid than hot brew in Rao and Fuller's study.
5. Taste side by side. Brew a light and a dark roast, or a washed and a natural coffee, the same way and compare. You will quickly learn where your preference sits.

Disclosure: this site is published by Mamre Blue Coffee, a Jamaica Blue Mountain estate (see about us), so we rely on official and independent sources for the facts on this page.