Acidity in Coffee: A Sign of Quality or a Brewing Mistake?

"Acidity" is the most misunderstood term when it comes to coffee. For some, it’s a sign of quality; for others, it’s the reason an espresso ends up down the drain. Both are right, because they’re talking about two completely different things.

One type of acidity comes from the bean. The other is something you don’t want in your espresso, and it’s created right in your machine.

Acidity as a Quality Indicator

All coffee naturally contains acids. The most important ones are citric acid, malic acid, phosphoric acid, and chlorogenic acid. They form in the coffee cherry during ripening and partially survive the roasting process.

How much of this ends up in the cup depends on three factors:

• Growing altitude. The higher the altitude, the cooler the climate, and the slower the cherry ripens. Slow ripening allows more time for acids and sugars to develop. That’s why coffees grown at 2,000 meters have a livelier profile than those from 800 meters.
• Processing. Whether the cherry is washed immediately after harvest or dried as a whole fruit helps determine how pronounced the acidity is. More on this below.
• Roast level. Acidity breaks down during roasting. A light roast preserves it, while a dark roast destroys it. That’s why an Italian espresso tastes barely acidic, whereas a light filter coffee tastes distinctly so.

The key point is this: In cupping, the Specialty Coffee Association does not evaluate the quantity of acidity, but rather its quality. A coffee can have a lot of acidity and still score very highly if it’s clean, sweetly integrated, and pleasant. Conversely, low acidity can be rated poorly if it comes across as flat or dull.

Good acidity tastes like something: lemon, apple, berry, apricot. It is backed by sweetness and has a long, pleasant aftertaste. In technical jargon, this is called “juiciness,” and it is exactly what you’re paying for in a specialty coffee.

Acidity as a Flaw: Underextraction

If your espresso tastes sharp, thin, and unpleasantly sour, in the vast majority of cases it’s not the bean’s fault. It’s due to the extraction.

During brewing, the coffee’s components are released one after another. First come the acids, then the sugars, and finally the bitter compounds. If you stop the process too early, you’ll only get the first half. The result is a drink that lacks the sweetness needed to balance the acidity.

Common causes of under-extraction:

• grind size too coarse
• extraction time that’s too short
• too low a brewing temperature
• not enough coffee in the filter basket
• Channeling caused by uneven distribution of the ground coffee

This acidity is not a characteristic of the coffee. It is a brewing error, and it can be corrected.

Here’s how to tell the difference in a single sip

The most reliable test is the sweetness. If it’s completely absent, it’s due to the preparation. If it’s there and the acidity balances it, like with a ripe apple, then you’ll taste the coffee exactly as it’s meant to be.

The third scenario: sour and bitter at the same time

There’s a variation that many people aren’t familiar with. When coffee is roasted too dark or kept warm for too long, chlorogenic acid breaks down. Among other things, this produces cinnamic acid. It tastes both sour and bitter at the same time, and it’s the most unpleasant form of acidity in coffee.

If you’ve ever tasted coffee that’s both sharp and bitter, that’s usually what it was: a roast that’s too dark or a pot that sat on the warming plate for two hours.

Processing plays a key role

What happens to the coffee cherry after harvest shapes the flavor profile almost as much as the roast. Four methods are commonly used, and each produces a different type of acidity.

Washed

The pulp is removed shortly after harvest; the remaining fruit mucilage is fermented in water tanks, then the bean is washed and dried.

Because the fruit is removed early, you taste the coffee itself: variety, soil, and altitude. The result is clear, transparent, and precise. The acidity stands out most distinctly in washed coffees because there is less sweetness from the pulp to buffer it. Washed Ethiopian coffees are therefore considered the benchmark for floral clarity, but if prepared incorrectly, they can also become sharp the fastest.

Natural

The whole cherry is dried, often for two to three weeks on raised beds. Only then is the dried pulp removed. During drying, the bean ferments in its own pulp.

This results in more body, more sweetness, and pronounced berry-like fruit notes. The acidity is often similar to that of washed coffees, but it feels softer because the sweetness carries it. Natural coffees are more demanding to produce: every unripe cherry increases the risk of fermentation errors, which are immediately noticeable on the palate.

Honey and semi-washed

The middle ground. The skin is removed, but some of the sweet fruit pulp remains on the bean during drying. Depending on how much remains, the coffee is classified as White, Yellow, Red, or Black Honey.

The result lies between the other two: more sweetness and a syrupy texture than washed coffee, and more clarity than natural coffee. The acidity remains lively but takes on a caramel base that rounds it out. The name has nothing to do with honey; rather, it describes the sticky surface that forms during drying.

Wet-hulled (giling basah)

The Indonesian method. The parchment is removed while the bean is still moist, after which it is dried to completion.

This results in a very distinctive character: full body, syrupy depth, and earthy and spicy notes. Wet-hulled coffees have the lowest acidity of the four processing methods, making them appealing to anyone who tends to avoid fruity notes.

In a nutshell

A note on classification: These classifications are general trends, not hard and fast rules. A washed coffee from 1,200 meters may be milder than a natural from 2,100 meters. Altitude, variety, and roast always play a role.

What to Do If Your Coffee Tastes Sour

Proceed step by step and change only one thing at a time:

1. Grind finer. This is the solution in nine out of ten cases. For espresso, adjust the grind by one or two clicks, then reassess. Our article on the perfect grind size explains how to systematically find the right grind size.
2. Check the extraction time. For a double espresso, it should take 27 to 32 seconds to reach the target volume. If it’s significantly faster, that means under-extraction.
3. Check the brew ratio. 18 grams of ground coffee should yield 36 to 45 grams of espresso. Weigh in grams—don’t estimate in milliliters—because the crema skews the volume.
4. Increase the temperature. Light roasts are less soluble and can handle 93 to 94 degrees, some even higher.
5. Improve distribution. Loosen the ground coffee with a WDT tool before tamping. Uneven distribution leads to channels through which the water shoots without extracting.
6. Check the water. Very soft water with low carbonate hardness makes acidity seem sharper. Medium-hard water buffers it.

If, after following these steps, acidity is still present—but now accompanied by sweetness and body—that’s exactly what the coffee is meant to be. Then it’s no longer the machine’s fault.

Milk makes fruity coffees more approachable

One point that’s rarely mentioned in Germany: Fruity coffees pair exceptionally well with milk. The milk fats and lactose smooth out the acidity and carry the fruity notes.

A cappuccino made with an Ethiopian natural-processed coffee doesn’t taste like chocolate, but rather like berries with cream. A semi-washed Colombian coffee yields a cappuccino with notes of caramel and dried fruit. Anyone who has only ever known cappuccino as a chocolatey drink will experience something different here.

The common assumption that fruity coffees should only be drunk black is therefore incorrect. When paired with milk, they’re simply a little different than you might expect.

Which coffee matches which preference?

If you like acidity and are looking for fruitiness:

• Hochlandjuwel, Ethiopia Guji, Natural. Rosehip, cherry, blueberry. The fruitiest in the lineup.
• Hochlandblüte, Ethiopia Sidama, washed. Floral and crisp, with clean fruit notes.
• Feldberg, Colombia, semi-washed. Panela, almond, dried fruit, with a juicy acidity.
• Hochlandsonne, Colombia Cauca, washed. Jasmine blossom and citrus.

If you’d rather avoid acidity:

• Hornisgrinde, Brazil, natural, medium roast. Marzipan, milk chocolate, vanilla. Very low acidity.
• Ätna, dark roast, from southern Italy. Dark chocolate and nougat.
• Vesuv, dark, with a Canephora blend. The boldest, with almost no acidity.
• Bergkraft, with wet-hulled Gayo from Indonesia. Chocolatey and full-bodied.

A note on this: Coffee always contains acids, even dark roasts. There is no such thing as a completely acid-free coffee. What differs is how pronounced the acids are. That’s why we don’t label any of our coffees as “acid-free,” but at most as “very low in acidity.”

Frequently Asked Questions

Is acidity in coffee bad?

No. In specialty coffee evaluation, acidity is a distinct quality criterion. It’s not the amount that’s evaluated, but the type: clean, sweetly integrated, and pleasant—or sharp and flat.

Why does my espresso taste sour?

It’s usually under-extracted. During brewing, the acids dissolve first, followed by the sugars. If the brew is stopped too early, the sweetness is missing. Grind finer and check that 27 to 32 seconds elapse.

What is the difference between fruity acidity and sour acidity?

Fruity acidity is backed by sweetness, has a juicy texture, and a long finish. Flawed acidity tastes thin, sharp, and cuts off abruptly in the aftertaste. The most reliable test is the sweetness.

Which processing method has the least acidity?

Wet-hulled coffees from Indonesia tend to have the lowest acidity, along with a full body and earthy spice. Washed coffees exhibit the most pronounced acidity, while naturals and honey-processed coffees fall somewhere in between.

What is the difference between washed and natural?

With washed coffees, the pulp is removed shortly after harvest, resulting in a clean, transparent cup. With naturals, the entire cherry dries around the bean, resulting in more sweetness, body, and berry-like fruit notes.

What does “honey process” mean?

The skin is removed, but some of the sweet fruit pulp remains on the bean during drying. The result falls between washed and natural: more sweetness and a syrupy texture than washed, more clarity than natural. The name refers to the sticky surface, not to honey.

Do dark roasts have less acidity?

Yes, some of the acids break down during roasting. However, very dark roasts can develop cinnamic acid, which tastes both sour and bitter.

Can you drink fruity coffee with milk?

Yes, and it often creates something special. The milk smooths out the acidity and carries the fruity notes. A cappuccino made with an Ethiopian natural-processed coffee tastes more like berries with cream than chocolate.

Does harder water help counteract acidic coffee?

Water with slightly higher carbonate hardness buffers the acidity. Very soft water makes the acidity seem sharper. For most coffees, soft to medium-hard water is the best compromise.