Determining and Influencing Acidity in Coffee

Among roasters, there is much talk about the acidity in coffee - and this with shining eyes. Is it fresh? Is it fruity? Is it pleasant? The more you pay attention to the acidity in coffee, the more you will notice that there is a big difference between aggressive sour taste that has spoiled many coffee experiences for you and the fresh acids that can give coffee its special taste. It is no different with coffee than with other drinks or fruits. For example, apples range from the green sour ones that make everything in your mouth contract to the mealy and papery ones without any acidity. Take a moment to think about how your favourite apple tastes. For example, we quite like Braeburn - with a fresh invigorating acidity and at the same time pleasantly sweet, but not too sweet. 

Acidic or bitter coffee? 

It is often difficult for us to distinguish whether something is sour or bitter. But especially for you as a barista and roaster, it is important to know and taste the difference. Because you can influence the balance of acidity and bitterness both in roasting and in making coffee. Test with a few sour or bitter foods and drinks to feel how they taste in your mouth, where on your tongue or in your mouth you taste them. Bitterness often tastes somewhat dry and lingers in the mouth. 

Initial assessment of acidity in coffee 

Take a sip and spread it in your mouth. How pleasant is the acidity? Does it bother you? Or do you actually quite like it because it is invigorating and refreshing or has something interesting about it?

How intense is the acidity? Does it spread immediately in your mouth or does it overshadow everything else? Or is it very delicate and mild? 

How does the acidity taste? What do you like? 

Look at the wheel below and consider which of these expressions you taste in your coffee. And above all - which of them do you like, and which do you not? 

Typical Acids in Coffee 

Citric Acid 

Citrus-like acid, reminiscent of orange, lemon, or sometimes grapefruit. You can often find this in Arabica coffees from higher altitudes. 

Malic Acid 

This acid is reminiscent of apple or pear. It is somewhat sweet and crisp. It often also reminds of stone fruits. 

Phosphoric Acid 

This acid can further enhance the sweetness in coffee. Tropical fruits like mangoes are typical representatives of this acid.

Acetic Acid 

This is vinegar-like acid. Certainly not what you want in large amounts in your coffee. However, in small amounts, it can have a pleasant subtle sharpness or the kick of lime-like flavour notes. 

Tartaric Acid 

These acids are typically found in grapes and can lead to wine-like or grape-like notes in coffee. 

Chlorogenic Acid 

This acid is largely responsible for how strongly we perceive the acidic taste in our coffee. It is significantly reduced during roasting.

Acidity in Coffee and Stomach Issues

In fact, it is not the acids that cause heartburn in individuals when drinking coffee. Recent research shows that these are components of coffee oils (so-called C5HT's). These stimulate stomach acid, which can lead to heartburn. Those who have problems with this can try decaffeinated coffee or dark-roasted coffee. 

Influencing Acidity in Coffee 

Already in the selection of green coffee beans, you influence the acidity in coffee: Arabica generally has more acidity than Robusta, highland coffee more than lowland coffee, East African varieties more than Brazilian ones. When roasting, it's quite simple: acidity decreases with roasting. So, the darker you roast your coffee, the lower the acidity - but be careful, with the second crack, bitterness builds up again, which you probably like even less than the acidity. In addition, you have a great influence on acidity and bitterness when preparing coffee. 

The coffee is too acidic if you: 

- use water that is too acidic

- grind too coarse and the coffee flows through too quickly (under-extraction)

- use too little coffee

- the water temperature is too low

The coffee is too bitter if you: 

- grind too fine and the coffee flows too slowly (over-extraction)
- use too much coffee
- the water is too hot
- you haven't cleaned the espresso machine for too long