Acidity in coffee - What is it, and why?

coffee acidity

The acidity in coffee is always a cause for discussion. 

Some love it, others like to do without it. However, acid is an essential component of every coffee and is responsible for a taste balance. I met up with a good friend that is a coffee roaster in Bulgaria, and I`ll let him explain why acidity is so important and define what good and bad acids are in coffee.

I hear “hipster coffee” again and again when people talk about cafes that serve coffees that do not meet the well-known norm. 

Often the criticism begins with the fact that these coffees are “just sour” and have nothing to do with coffee. 

As a coffee roastery and coffee school, we experience the same phenomenon again and again when people talk about a “really good espresso”. 

Then this is often accompanied by the idea of ​​a classic southern Italian espresso all’Italiana. 

Of course, coffees with more acidity are not a trend – and if so, it would be one that has come to stay. 

We see it much more as a development that we as consumers are getting to know more and more perspectives on coffee. 

An example: When our partners from Nicaragua are with us and taste espresso, they hardly manage to finish the coffee.

Acidity in coffee: is it all a question of perspective?

Most people get to know coffee anew while traveling. 

Be it in the cities with a high density of specialty cafes, or in coffee countries themselves.

Coffee usually tastes different from what we drink in Central Europe. 

In coffee countries, in particular, much filtered or boiled coffee is drunk; espresso is much less common.

In Central Europe, espresso made from rather dark roasted beans is still what many consider to be a good espresso. 

“A real espresso” often means that they are really dark. 

When I went to a specialty coffee shop in the US for the first time in 2009, I had a very bad espresso. 

It was just sour – and, although I was on the acid trip back then, I could hardly drink the espresso. 

The double ristretto was overdosed and under-extracted, and that with a light roast. I didn’t like it, wouldn’t find it tasty today either, but the coffee shop was doing well and the guests liked the coffee.

Taste is learned. What we find tasty and what we don’t is determined by our socialization, by our contact with a lot or a few foods. 

Whether we like coffee with little or a lot of acidicy depends primarily on what we already know and, secondly, how open we are to what does not correspond to our experience.

And only then does our qualification begin, whether we like the coffee or not.

Acidity in coffee splits the spirits and the palate

When I drank my first acidic espresso from a well-known English roastery, I found it strange at first. 

I should still taste a lot of flavors if I believed the package. 

I literally had the feeling that I wanted the coffee to be good – so from then on, I looked for acidic coffees.

When I drank a more normal coffee with barely noticeable acidity, something was missing. 

The coffee was dull, single track, it happened: Nothing. 

My tongue wasn’t triggered.

“At the same time, it became clear that acidity is only part of the whole taste experience. It’s about balance. It’s about sweetness. It’s about complexity, the clarity of the aromas, the intensity of the attributes, and the pleasant texture”.

Anyone who is interested in specialty coffee has probably already drunk coffee with more acid than usual.

Some stay with it, others go back. Some go back and know what they have learned. 

The others go back and have very little taste for this type of coffee – and that brings us back to perspectives.

The acidity discussion divides the minds, the palate, and goes in circles. 

That is why we explain in the following points what acid is in coffee, what it does, what it can do, and where it comes from. 

The pH of coffee - Sour or?...

Regardless of the topic, we can only describe things as precisely as we can express them. 

Sometimes the language presents us with special challenges. 

In Swiss German, the noun acid ( Süüri ) is used much less than the attribute Sauer ( suur ). 

Many things are just suur. Often suur is also used as an attribute for bad coffee.

coffee ph coffee scale

The case is very similar in Europe, only – at least in product descriptions – acidity is used more often than sour

Whether it is of a linguistic nature or not – technically they are also different things.

“Acidity in coffee is positive. Is a coffee but sour (acid), which is a negative description”.

Acids, on the other hand, are the acids, up to 40 of which can also be measurably detected in a coffee. 

Why is the acidity-sour distinction so important?

Because technically they’re two different things. 

Acidity (or acidity) refers to the taste profile of the coffee.

Sour refers to the pH of the coffee. 

“With a pH value of approx. 5 ( 4.85 – 5.1 pH ), coffee is a mildly acidic drink. Tomato juice (pH 4) and lemonades (pH 3) are significantly more acidic. Clear, because the pH scale is logarithmic – i.e. a value of 1 pH difference is 10x higher / lower. A lemonade is 100 times more acidic than coffee”.

Even if the assumption is obvious: the amount of taste-perceptible acidity has no influence on the pH value of the drink. 

In this case, a strongly acidic espresso from Kenya has the same pH value as a dark roasted Malabar. 

So the difference between these coffees lies in the sensation of acidity, but they are both acidic.

What acids do we taste in coffee?

Of the almost 40 acids that can be found in green coffee, it is the chlorogenic acids that make up the largest proportion. 

They occur with between 6 – 7% in Arabica and just under 10% in Robusta. 

In relation to caffeine (1-2%), the content of chlorogenic acids in coffee is significantly higher.

Chlorogenic acids are a family of different, naturally occurring compounds – those that degrade during roasting (mono-caffeoyl) and those that hardly changes during roasting (di-caffeoyl).

During roasting, chlorogenic acids break down into the bitter-tasting chlorogenic acid lactones

And since Robusta has more chlorogenic acids than Arabica, it is already more bitter than Arabica.

Many of the acids present in green coffee do not survive the roasting process

The longer and the darker it is roasted, the more the perceptible acids break down.

In terms of taste, however, we can only distinguish a few acids from all the existing ones. 

Citric acid 

The acid with the highest concentration in coffee. 

It is the acid that occurs in every coffee – and, depending on the intensity, can be more easily or more difficult to recognize as such. 

Citric acid occurs naturally in the metabolism of the plant, it plays an important role as an energy supplier. 

The taste is reminiscent of – how could it be otherwise – citrus fruits (lemons, limes, oranges).

Malic acid

We find malic acid in apples, pears, and rhubarb.

In wine production, it is replaced by lactic acid in malolactic fermentation, as it can have an aggressively acidic property. 

In coffee, it often occurs in a similar way to citrus acid, but a bit more palatable, more balanced, and for many in a different place on the tongue.

Phosphoric acid

Phosphoric acid is not organic, but a mineral acid. I

t should be absorbed through the composition of the soil and/or through the type of fertilization of the plant. 

The acid is often a bit tart, sometimes tingly, and harsh. We often have them in Kenyan coffees.

Acetic acid

Acetic acid can be extremely unpleasant in high concentrations. 

It occurs when the coffee causes a defect from uncontrolled fermentation. 

New types of post-processes and fermentation in coffee also bring more acetic acid into the taste. 

If this process takes place in a controlled manner, then a certain degree of acetic acid has a fruity effect and contributes to a positive overall impression. 

Lactic acid

The quality of the lactic acid in coffee is similar to the acidity of quark – a bit tart, rather sour, but heavy. 

Through targeted fermentation of the coffee in the post-harvest process, the proportion of lactic acid can be increased, which has an influence on the softness of the texture.

3 takeaways at this point:

  1. One of the most exciting aspects of the acids in coffee is the combination of different acids – in the same coffee at the same time. If several different acids are present at the same time, the taste impression is also significantly stronger. We then talk about complex acids.
  2. Coffee is sour when it is not supported by sweetness. Then we talk about inferior quality coffee.
  3. a coffee without acid results in a very flat coffee. Or you ask yourself the question – how would a white wine taste without acid? Just flat. 

Does acid hit the stomach?

The subject of health and coffee would deserve a completely separate contribution – if the evidence were really overwhelming against coffee. 

Coffee is attached to about as many negative effects as there are positive ones. 

The topic is felt to be washed up in the summer slump and then seeps away again for a year. 

One thing is certain: everyone reacts differently to coffee.

I thought I would include this interesting video where you get some valuable feedback about how to taste coffee that will help explain the acidity.

Where does the acid in coffee come from?

In the processing steps from the coffee tree to the cup, there are various passages where the coffee can retain or lose its acidity. 

Everything starts with the plant.

Plant / cultivation

Cellular respiration is responsible for the growth of plants and the development of cherries. 

A wide variety of acids are formed in the process. 

The formation of these acids is influenced by the growing conditions.

One factor, in particular, plays a major role here – temperature

At higher altitudes, or at a greater distance from the equator, and/or in shady locations, the temperatures are lower.

This slows down the growth of the coffee plants and their cherries. 

At a slower growth rate, the plant will focus more on reproduction and therefore invest more in growing healthy seeds. 

The slower-grown coffee seeds show more proteins, sugar, fats, and also acids than those that grew faster.

Conversely, the caffeine content is reduced with slowly growing coffee.

Species and varieties

Arabicas have a higher acid content than canephora’s (robustas).

There are also differences within the varieties, especially Arabicas, but these are very minor. Parainemas, for example, a hybrid from Honduras, shows significantly more citric notes under the same growing conditions than the IHCAFE90, another hybrid. 

I was once able to taste a test series of different varieties that were grown under the same conditions as an exporter.

The Parainema stood out. However, the differences are otherwise much smaller and can be neglected here.

Post-harvest processes

In short: de-pulped, fermented, and washed coffees have the potential to show more perceptible acidity than coffees that have been dried inside the cherry – if the cherry is brought to the drying stage directly.

The storage of the cherry (barrel, barrel, tank, sack, etc.) can mainly affect the acetic acid level.

Post-harvest processes, however, do not regulate the acids so much, but add new flavors or can mask existing ones.

Picking coffee

Roasting coffee

Longer roasting times and higher final temperatures minimize the organic acids. 

However, the acetic acid peaks for a brief, unstable moment as coffee is roasted into the second crack. 

All other organic acids degrade over the duration and increasing the temperature of the roast.

roasting coffee infograph temp readings
The yellow curve accentuates the acids, the red curve leads to a balanced coffee, while the blue curve reduces many acids.

preparation

While the type of acid is determined by the factors already discussed, the preparation is responsible for the amount of acid extracted. 

Grinding degree, brewing temperature, brewing time, pressure, and turbulence during brewing influence the total acidity that can end up in the cup if it is not buffered by the water.

water

Buffer water with high alkalinity, or neutralize the perceptible acids in coffee. 

At the same time, they also pull the pH towards basic. 

So the water manages to change acidic and acidic at the same time and is, therefore, the invisible but powerful component. 

Perceived acidity in espresso, filter coffee, and fully automatic coffee

When we talk about “acidic coffee”, what drink are we talking about? 

This aspect is also strongly linked to our experience of and our expectations of coffee. 

Personally, I almost exclusively think of filter coffee when I think of coffee.

Many find it easier to accept acid in filter coffee. 

This has primarily to do with the fact that the coffee concentration in the filter coffee is significantly lower ( approx. 1.5% of the beverage is coffee, the rest is water ) than in an espresso (approx. 10% of the beverage) Coffee). 

Espresso is an incredibly intense, concentrated drink. If a coffee shows little acid in the filter coffee, it will have a lot more acid in the espresso. 

In our roastery, we only use acidic coffees for espresso when we can also detect a lot of sweetness – this pair then creates a taste balance. 

Without this balance, the coffee would be primarily sour and difficult to enjoy. 

But even with balanced coffees that are acidic and roasted even lighter, the perceived acidity remains.

However, the perceived acidity of filter coffee plays a less dramatic role for many. 

Since filter coffee is a diluted coffee beverage, a perceptible acidity is good for the coffee to get structure and tension. 

Filter coffee would be very flat without acid.

Again, it looks different with the fully automatic coffee machines. 

If you work with acidic coffees, you will not enjoy the espressos as much.

Why?

In fully automatic coffee machines, which usually brew at temperatures below 90 ° in household use, acidic coffees taste even sourer.

The brewing temperature is low and the grind is relatively coarse so that less sweetness and less texture-forming starch particles can be extracted.

For example, light roasted coffees taste exclusively sour on a fully automatic household machine. 

That is why we roast differently for fully automatic requests and also train this in our consultations.

Good acids, bad acids

Good acids give the coffee

  • Freshness
  • complexity
  • tension

and often make us think of specific fruits.

Bad acids

  • act aggressive
  • dry out
  • can be pointed and piercing

This is often the case when there is little or no sweetness in the coffee.

“Sweetness supports acidity, said a former fellow juror to me. When there is a lot of sweetness, the acid becomes more and more exciting. The opposite is also true”.

The challenge of communicating acid positively

We coffee makers: inside, we like coffees that are clearly acidic. 

We work with green coffees that they already bring with us and roast the majority of the coffee’s light to medium-light.

This type of roasting retains a lot of acids in the coffee.

Of course, we all like coffees, which are sometimes milder, sometimes a little more chocolaty and less acidic. 

For example, our APAS or Henrique from Brazil – both coffees that, by our definition, have less acidity.

For our courses, in particular, we take the coffee from the APAS cooperative, as it has a more classic, nutty-chocolaty profile with less acidity. 

This profile is known to most course participants: inside and is much less challenging than if we were working with a lightly roasted specialty espresso.

As has already become clear up to this point, it is not easy to communicate acid positively – for the reason that there is often a negative attitude towards it. 

We do not see it as our task to fight it convulsively, which is not productive.

And above all, we are staunch opponents of a taste dictatorship.

Tastes are individual and change only slowly.

We see another way of making specialty coffee – with little or much acid – tasty.

1. Less focus on acid in communication 

In the beginning, I wrote that the discussions about acidity in coffee kept going in circles.

Maybe it’s because there is sometimes a little too much focus on this topic?

In conversations, it often sounds as if good coffee only exists between the opponent’s acidity and bitterness.

But anyone who has dealt more with the topic knows that there are worlds of taste, complexity, and balance in between.

So why not focus on the body and texture? 

This coffee attribute is so special because it’s the only one that hasn’t been learned because we feel it and don’t taste it.

Without any prior knowledge, anyone can feel whether coffee is creamy or watery.

Whether a coffee has a citrus or malic acid is a much more complex matter that requires training.

2. Describe acid differently

When I took part in the Swiss Barista Championship in 2010, I would have described the coffee as “as if it only tasted like acidic toilet cleaner”. 

That’s what a somewhat challenged viewer meant after my presentation. 

I, who was new to the business at the time, went on defense first because I liked my coffee. 

But when I looked at my descriptions again, they were all quite similar. 

It was about citrus notes, tangy, “citric”, clementines and citric acid.

If I were to describe the same coffee again today, I would do it significantly differently. 

I now know that acid is only part of it, that texture is the focus for me, and similar descriptions are not as precise.

This is how we describe coffee differently today – a simple lever is that we associate more acidic coffees with fruits.

In El Colibri, a Peruvian coffee that we roast as espresso, we find a tartaric acidityi.e. a tartaric acid. 

If we were to describe coffee to a wider audience as having “tartaric acid” in it, that would be more confusing than it helpful. 

The association with wine is there, and very few have ever tasted tartaric acid on its own. 

So it makes sense to switch to grapes that are full of tartaric acid. The coffee generally has lighter flavors, so we opted for raisins and “white wine-like”.

3. Accept that acidity is just not everyone’s cup of tea

Sounds logical? Maybe, it is still not easy.

Many appreciate specialty coffee for the variety of flavors, for the otherness, for the new sensory experiences, and perhaps the stories behind the coffee.

When I first prepared a specialty espresso for a friend in 2009, the coffee was really very acidic. 

Maybe he was very angry, but then I was looking for something different. 

Said friend grimaced, looked at me confused, but tried to find something besides this aggressive acid.

The acidity was immediately the focus of the discussion – not the variety, not the roast, not the origin, not the chic branding. 

I tried to explain to him why there was acid in it, why it was less intense in other coffees, and why it was positive.

I could never convince him. 

At first, I even thought that I had to.

Today he drinks Henrique from us and is incredibly satisfied. 

A medium-dark roasted coffee with less acidity. 

Doing his thing. 

Over the years I have learned that acid is often at the center of discussions in specialty coffees. 

So it makes sense for us today to show something more classic, nuttier coffees, or the opposite – extremely aromatic coffees, for example, naturals from Ethiopia.

Coffees that smell so intensely different that we first talk about the aroma, make the wine comparisons, recognize the complexity, and at some point then also talk about the acidity.

Conclusion

Explaining to someone that acidity in coffee can be positive is a difficult approach to explaining specialty coffee. 

The arguments – albeit coherent – rarely meet with approval. 

But if the focus is on the texture and the aroma, the first hurdle is over.

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