Acidity is the taste that separates a complex coffee from a flat one, and the one that roasters disguise as “brightness” so as not to frighten anyone. The professional training documents teach how to recognize six acids. Phosphoric, the fizzy freshness of Kenyan coffees (SL28). Citric, the lime of washed coffees from Ethiopia and Central America, dominant in a fresh harvest. Malic, green apple, rounder, in certain washed coffees from Burundi and the Dominican Republic.

professional training document, acidity in coffee, p. 3

Lactic, creamy, in Brazilian naturals. Acetic, winey, the signature of Harrar naturals, which is easily mistaken for body. Quinic, the only undesirable one, born of the breakdown of CGAs, which rises with dark roasts, aging and the cold cup, and is abundant in canephora. Citric and malic come from the fruit; acetic and lactic are fermentation products, which explains why they are the signature of naturals and of long fermentations; phosphoric is mineral.

professional training document, acidity in coffee, p. 2-3; Yeager, Batali, Guinard, Ristenpart, Critical Reviews in Food Science and Nutrition (2021), Acids in coffee: a review of sensory measurements and meta-analysis of chemical composition

Measurement and perception do not coincide. The pH of a filter coffee is around 5, that of a canephora a little higher. But this figure tells less than it seems to.

pH measures only one thing, free protons, that is, the acidity already dissociated in the liquid. Perceived acidity depends on it, but it also depends on titratable acidity, which additionally counts the reserve of acid still bound. It depends as well on sweetness, which masks it, and on bitterness, which hardens it. Four parameters for a single sensation.

Roasting muddies the trail a little more. It sharply lowers CGAs and citric acid. It raises quinic and acetic. It also shifts the CGA isomers, so that the acid profile on exit is no longer that of the green bean.

Temperature adds its effect. The same coffee tasted at 70 and then at 40 °C does not show the same acidity. This is why every protocol requires going back over the bowls as they cool: tasting only once means seeing just one moment of the coffee.

There remains the question that would decide everything. Can perceived acidity be predicted from an assay? The review by Yeager and coauthors (UC Davis, 2021) compiles the published measurements and answers no. It finds no stable relationship between the content of this or that acid and the acidity that a panel reports.

Yeager et al. 2021; Yang et al. 2026, p. 7; professional training document, tasting guide, p. 6