Let’s find out what’s behind this word, that is so used (and oftern abused) in the coffee world.
Acidity is a hot topic when it comes to coffee, because it is one of its most peculiar characteristics but also very controversial. But what is an acidic coffee? Is coffee bad for the stomach? Is acidity a good thing or a bad thing? Is there a non-acidic coffee?
This article will answer all these questions.
Before venturing into the specific part of the topic, we need to time-jump to high school chemistry classes. The acid of a water-based solution is measured on a pH scale ranging from 0 to 14. Any solution with a value below 7 will be defined as acidic; on the contrary, if above 7, then it will be basic.
Within an interval ranging between 4.85 and 5.10, the coffee’s acidity is not so outstanding: it is more or less equivalent to that of beer and it is lower than that of fruit juices and wine. Answering the second question, if coffee is bad for the stomach, we can now affirm that if the drink that we just mentioned, do not affect your stomach negatively, than probably your excessive stomach acid is not CAUSED BY COFFEE.
In fact, research has shown that coffee is not the cause of health problems such as heartburn, gastric reflux, etc. However, it is certainly recommended avoiding ALL acidic drinks, if these conditions are already present.
Now let’s go deeper into the topic: acidity is nothing more than the result of fermentation which then starts to create the aromatic profile that we will find in the cup of coffee. As a matter of fact, the acid part influences the flavor as well as the aroma and to understand exactly how, we will have to analyze its chemical composition.
The organic acids that we will most often find in coffee are the following:
Malic acid: it has the typical taste of green apples
Citric acid: it recalls the flavor of citrus fruits and is found in Arabica beans, usually grown at high altitudes
Acetic acid: it is created during the roasting process, like the lactic acid; if in small amounts it recalls vinous and red fruit notes, otherwise it can become unpleasant.
Lactic acid: no, we are not talking about the pain after physical activities; in food it is nothing more than glucose converted into acid when it degrades. In the mouth it creates a round and creamy sensation
Phosphoric acid: it is the only non-organic acid and it develops in plants that grow on volcanic soils and are therefore rich in sulfur; it is an acidity enhancer and recalls an effervescent sensation
Then we have the chlorogenic acids which represent the good and bad of each coffee bean. Believe it or not, they are powerful antioxidants but some of them, during the roasting process, turn into quinic acid: this does not have a particularly good taste and on the contrary, creates astringency and acidity. We usually find it in dark roasted coffees or in stale ones, kept warm by a heat source.
After this examination we can answer the question "is there a coffee that is not acidic?". No, indeed coffee would not be coffee without acidity.
Actually, there are many factors that influence the presence, quantity and type of acidity we find in coffee beans.
The most important factor that somehow includes all the others is certainly the origin: each coffee plant sprouts and grows on a certain soil, at a certain altitude, in the shade or in the sun.
All this clearly affects the faster or slower formation of acids, sugars, in general of organic substances and consequently of flavors. In fact, plants that grow slower have more time to develop more complex characteristics.
Here the climate plays an important role as well, specifically the temperature in relation to the altitude.
The variety is significant too: for example, Arabica beans are from the start low in chlorogenic acids and consequently the sour taste sensationon on our palate is not pronounced.
Going even deeper, we can say that the Arabica Bourbon variety, with its smaller beans, turns out to be more acidic with more complex flavors. On the other hand we find the Arabica Typica, which has more neutral and warm notes.
Another key factor is surely the processing method: with the “natural” one, which is also the oldest, the fruit of the coffee called drupe is dried in the sun for 3/5 weeks in a natural way. Once it is dried up thanks to the heat, it has to reach around 12% moisture.
At this point the dried part is removed mechanically, with decorticators. From the description we can deduce that with this method, considering that the coffee bean stays in contact with its pulp for longer, the perceived acidity is balanced with sweetness.
With the “washed” method, also known as wet, the drupes are placed in water tanks and then deprived of the fruit flesh with specific machines, called depulper. So after that, the beans still wrapped in their parchment, are immersed in other tanks for the fermentation process, at the end of which the remaining mucilage will be removed. The coffee beans will finally be dried in the sun on raised beds or on a concrete drying patio.
This method normally brings out more the acidity naturally present in coffee, as the sugary component of the pulp and mucilage is “washed away”in different stages during the process.
Another factor that affects acidity is the roasting process, but this is another story, which we will soon read on this channel. Stay tuned to continue following the map of flavors and aromas found in the cup of coffee.
To be continued ...
This and other topics are discussed during our Sensory and Brewing Skills courses.