Why coffee is acidic and how to influence the acidity of coffee


In coffee, as in wine, we can find many combinations of flavours and aromas. You will have noticed that some coffees taste more sour. This coffee acidity is then referred to as coffee acidity. Some coffee drinkers absolutely love these acidic coffees, while others choose coffees with only minimal acidity. In coffee, acidity is an important component of the overall flavor profile. It adds depth and complexity in other layers of flavors in your cup of coffee.


Acidity is a natural substance in coffee, as it is in many foods. For example, in lemons, vinegar or yogurt. Coffee contains hundreds of acids such as the well-known citric and malic acids. How sour coffee tastes is influenced by the roasting, variety and preparation of the coffee.


The resulting acidity of coffee is a combination of several factors. Firstly, the acidity content itself , which is naturally produced and depends on the variety, growing and processing methods, theroasting style and, of course, thefinal preparation and other influences. For simplicity's sake, let's consider the 4 most important factors in creating and defining acidity in coffee:

  • the type of coffee plant,
  • the processing of green coffee,
  • roasting style,
  • the preparation method.


Plant cellular respiration mainly results in the production of chlorogenic, citric, malic and phosphoric acids. All of this can be influenced by whether the plant is growing in the shade or at what altitude it is.

In shade and at higher altitudes, coffee tends to have higher levels of organic acids, chlorogenic acids, caffeine and sugars (sucrose). The slow growth of the plant under these conditions essentially allows more nutrients to enter the fruit, aka coffee, resulting in higher levels of organic acids in the coffee.

Of course, it also depends on the plant species and varieties, which play a huge role in acidity production. For the record,robusta coffee species exhibit much higher levels of chlorogenic acid (about double the amount) compared to arabica coffee. Chlorogenic acid is characterised by its bitter taste.

So coffee varieties in particular play an important role in the final taste in the cup. Different Arabica varieties produce different levels of organic acids (both sucrose and fructose), making them fundamentally different in terms of their acid profiles.

Inshort, we can say that Arabica tends to be more acidic than Robusta. In reality, however, it's a bit more complicated than that. We have tasted very acidic Robustas and, conversely, almost non-acidic Arabicas. In addition to the specifics of acidity in coffee species and varieties, take into account thegrowing region, as most varieties are characteristic of specific continents and regions. African coffees usually have a high acidity content.


How sour the coffee will ultimately taste is also greatly influenced by the methods used to process the coffee after harvesting. There are three basic methods of processing coffee:

  • wet (washed),
  • dry (natural)
  • and honey-processed.

All of these methods have a big impact on the resulting acidity of the coffee. Washed coffees usually have the highest overall acidity level. They taste very fresh, fruity, floral and acidic. This flavour is influenced by the fermentation in water and also by the fact that the sweet pulp is washed off the beans at the start when they are peeled and washed.

Natural processing leaves the coffee cherries intact. This tends to increase the sweetness in the cup, which in turn reduces the acidity. The coffee has stronger and more pronounced flavours. The sweet, honey, nutty and chocolate flavours are mainly found in these coffees.

Thehoney method of coffee processing is a combination between the wet and dry methods. With honey processing, the resulting cup of coffee has a smooth but distinctive body. Honey-processed coffee does not contain many sour notes, but rather is sweeter.


Coffee beans change their chemical structure through roasting, soeach type of coffee needs a different temperature and length of roasting. The resulting taste is influenced by temperature, air supply, the speed of the drum movement in the roaster and the goodness of the roast.

Medium roast coffee slowly dissolves the sugars during the roasting process and the resulting taste is then sweeter and the acidity subsides. Coffee that is roasted dark to strong tastes more bitter and chocolatey. During the roasting process, both citric and malic acid are broken down. Therefore, darker roasted coffees lead to a cup of coffee like espresso that is flatter in flavor and more oriented to the body of the coffee.

We indicate on the coffee package whether we roasted the beans for espresso or for filter. For espresso, a medium level of roasting is usual so that the espresso doesn't come out with too intense to astringent acidity. Espresso is naturally a very intense drink.

On the other hand, 'filter' roasted coffees are suitable for alternative preparation methods. In general ,if the coffee is roasted lightly and gently, it is more acidic and fruity. Such lighter roast coffees are very suitable for filter coffee preparation. It is in a cup of filter coffee that we can enjoy the layers of flavours, both sweet and sour, which are subtle yet clearly defined.


In the final analysis, it also matters a lot how thecoffee is prepared. Depending on the type of preparation, the coffee will eventually develop its flavours and aromas. You will notice that as the coffee cools it shows an increasing level of acidity. As the coffee cools, the quinide (tonic water as a phenolic compound) is converted to quinic acid, which affects the taste in the cup. Therefore, if you make a cold brew at home, look for more fruity and acidic notes.

During the brewing process , we can accentuate the acidity in the coffee by, for example, 'under-extracting the coffee'. This can be done simply by, for example, grinding the coffee more coarsely. Conversely, we can reduce the acidity and, conversely, increase the bitterness by slightly 'over-extracting'.

The simplest example is the preparation of espresso on a lever coffee machine. Ideally, the coffee should flow through the coffee in about 30 seconds. If you extract the coffee in less time, say 20 seconds, it will probably be very acidic. A longer extraction time , achieved by finer grinding, will produce coffee with a higher bitterness.


According to the SCA - the specialty coffee association, where we as a roaster are members and are trained in this, the intensity and quality of acidity is assessedwhen testing coffee. Beware - quality acidity does not have to be intense! But it certainly has to be complex.

If, for example, you could smell raspberry and nothing else in the coffee, immediately recognise it at first sight and detect nothing else in the coffee, this is simple non-complex acidity and therefore a lower quality acidity (even if raspberry is your favourite fruit). If, on the other hand, you detect different berries in the coffee, perhaps with a slight bergamot component, this is a complex acidity and therefore of higher quality.



Citric acid exists in high concentrations in citrus fruits. In fact, it can make up to 8% of the dry weight of these foods. You'll find citric acid in large quantities in green coffee, and its acidity level decreases during the roasting process. It is by far the most common acid found in all fruits and vegetables and is also the easiest to identify.


Malic acid has a taste that is most commonly associated with green apples. You can find malic acid in its purest form in rhubarb, green grapes or kiwifruit. Malic acid can be thought of as an unripe fruit flavouring. Malic acid is formed by cellular respiration. This gives it a persistent acidity from the start. The acidity generally decreases the riper the fruit becomes.


Tartaric acid is usually associated with grapes because of its high concentration in this fruit. The most distinctive feature of tartaric acid is its almost astringent taste in the mouth. In fact it is one of the main ingredients in sour confectionery. Higher levels of tartaric acid are typical in white dry wines of good vintages. The salt of tartaric acid, potassium bitartrate, develops naturally in the winemaking process and is commonly used in food preparation.


Acetic acid is quite special. Itis formed during the coffee processing and roasting process, and while not as glamorous or noticeable as citric or malic acid, it contributes to a good tasting cup. In addition to the very characteristic vinegar taste, it also has a pungent vinegar aroma.

This can provide a pleasant sharpness or lime-like aroma at lower roast levels, but tastes and smells like fermentation at higher concentrations. Vinegar in coffee probably doesn't sound very appealing, buta bit of acetic acid can make for a beautifully balanced tasting cup of coffee.


Although not as noticeable as citric or malic acid, lactic acid tends to change the textural aspect of coffee. Itmakes the coffee slightly creamy. Which also deepens the body of the coffee.


Now you have a pretty good idea of what the different acids are and what they taste like. But what does this have to do with the taste of coffee? The easiest way to understand acidity is to think of it as an abstract concept.

For example, orange acidity doesn't mean that your coffee literally tastes like oranges. Rather, its real meaning is that it'sas sour as an orange. Or blueberries are less acidic than lemons, so coffee with blueberry acidity would be less acidic than coffee with lemon acidity.


Some berries have similar values on the pH scale but taste completely different. For example, apples and oranges. So how does it work? In the case of apples and oranges, the predominant acidity in the respective fruits is different. Green apples are mainly composed of malic acid, while oranges are full of citric acid.

Imagine a beautiful light and lightly roasted African coffee. When brewed, it has a pH level of 4.6 on the scale. This includes grapes, peaches, plums, pineapples and so on. Then you'll notice that it leaves a tartness in the mouth that is characteristic of tartaric acid. You could probably define it as grape acidity.


The skill of detecting and describing flavours in a cup of coffee can be developed to some extent. How else but by training. We can only define flavours in coffee if we have already encountered them. This means that in order to better identify fruit flavours in coffee, we need to have our palate "calibrated" to the flavours of fruit.

For this reason,tasting not only familiar and recognisable fruits such as apples, but also familiarising yourself with exotic fruits When eating them, consciously perceive their taste and remember it. Everything you taste and smell is training for your perception of flavours and aromas. This will give you a greater 'vocabulary' to define the flavours in coffee.

To directly compare the fruit acidity with the acidity in a cup of coffee, you can prepare a special cupping. That is, acoffee tasting to which you add fruit tasting. Alongside the coffees you are tasting, prepare samples of the different fruits so that you can compare them together immediately and better identify them.


According to our data, two types of customers predominate: 80% of people dislike acidity in coffee and outright seek out non-sour coffees, and 20% of customers seek out fruity coffees. The modern approach in a coffee shop is to offer a suitable coffee for both types of customers. That's why in our shop you will also find two types of coffee daily, a non-acidic coffee on the first grinder and a fruity and fresh coffee on the second grinder.

Fruity coffees have much more to offer in terms of taste than coffees without acidity. With coffee it's like with wine or perhaps rums. If you are looking for quality and unusual flavours reach for a drier wine or rum. With coffee the analogy is with acidity.

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