What Gives Coffee Its Flavor? Part One: Acids and Acidity

Introduction

Want to know what gives coffee its taste? Interested in optimizing your cup of Joe to suit your individual preferences?  

It helps to have a basic understanding of why coffee tastes the way it does. 

There are five basic tastes: acidity (sourness), sweetness, bitterness, saltiness, and umami (savoriness). The last two aren’t usually present in coffee.

In this post, I will focus on acidity, explain how acidity affects your cup of coffee and provide some tips for those who want to refine their coffee-tasting palate.

What Gives Coffee Its Flavor? Acids and Acidity

Mostly we misunderstand when we mention acidity concerning coffee.

You might think of something sour, sharp, tangy, and relatively unpleasant, like pure lemon juice. But in coffee, acidity is often a desirable characteristic. 

In a well-balanced cup, it’s the sensation that can make coffee taste like biting into an apple: fruity, juicy, bright, refreshing. 

Coffee professionals use these words to describe the nuanced flavors and sensations that come from the over 30 individual acids present in a cup of coffee. 

Acidity in coffee is kind of abstract—in fact, you’re actually tasting perceived acidity because pH is not playing a role. 

Therefore, you’ll hear a good deal of poetics used to describe acidity in coffee.

Science doesn’t have all the answers for how different acids affect what gives coffee its flavor?

But it knows enough to conclude that not all acids taste great, and not all of them contribute to perceived acidity. So it’s really the combination and balance of different acids and other flavor compounds that provide that pleasant zing in coffee. 

As a whole, acidity is a counterpoint to perceived sweetness, and its presence prevents a cup from tasting flat. 

One way to think about this combination is by comparing it to homemade salad dressing.

The right proportion of, say, lemon juice to olive oil produces something more pleasing to the senses than the individual parts alone. 

Here are a few of the most essential acids found in coffee, and what gives coffee its flavor according to the pros.  

Tasting Tip  

Having trouble discerning acidity in your coffee? You’re not alone! Try tasting something you know is acidic, like a lemon. 

Pay close attention to the parts of your mouth that react to it and how they react to it. Then drink some coffee and see whether your mouth reacts in the same way. 

It also helps to take a sip of coffee, hold it in your mouth, and move your tongue around before swallowing it. 

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Everyone is different. But for me, acidity in coffee feels like a tart tingle on the tip of my tongue.

A mouthwatering sensation on the walls of my cheeks, which is the same feeling I get when drinking orange juice.

Coffee cuppers reviewing aromas
Coffee cuppers reviewing aromas

Chlorogenic acids

Most of the organic acid in roasted coffee comprises chlorogenic acids. This is actually a group of acids, not the name of an individual acid.

These acids are primarily responsible for perceived acidity—the zingy or sparkling quality—in a cup of coffee. 

The longer the coffee roasts, the more of these acids are being destroyed. So beans with shorter roast times we refer to as “bright” more often than beans with longer roast times. 

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Citric acid 

This is usually the second-most prevalent organic acid in roasted coffee.

It’s actually produced by the coffee plant itself, not by the roasting process (although roasting degrades it). 

The citric acid in coffee is the same as that in citrus fruit. As you might guess, it’s associated with citrus flavor notes, such as orange and lemon—even grapefruit when phosphoric acid is also present. 

Citric acid also contributes to the perceived acidity of a cup, and in high concentrations, it can make coffee taste unpleasantly sour.

Malic acid

This sweet, crisp acid contributes flavors of stone fruit (such as peaches and plums) and notes of pear and apple. 

In fact, this type of acid we can find in high concentrations in apples, making it familiar enough for some coffee drinkers to more easily distinguish it from other acids.

Quinic acid

Quinic acid forms as chlorogenic acids decompose during the roasting process

Therefore, it is present in higher concentrations in darker roast coffees than in lighter roast coffees.

This acid contributes to coffee’s body and perceived bitterness, producing an astringent (drying) quality. 

Quinic acid continues to form in a cup of coffee if it’s left to sit, which is why coffee that seats on a hot plate for hours (don’t do this) tastes bitter. 

It’s also present in more significant quantities in stale coffee than in fresh.

Caffeic acid 

This acid (unrelated to caffeine) also forms as chlorogenic acids decompose. It’s found only at low levels in coffee, but it’s thought to contribute to astringency. 

Phosphoric acid

We believe this inorganic acid to taste sweeter than most other acids.

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When combined with intense citrus flavors, phosphoric acid can mellow those flavors to taste more like grapefruit or mango. 

It can also add a cola flavor to coffee and contribute to the overall perceived acidity in a cup.

Acetic acid

The primary acid in vinegar, acetic acid, can give coffee an unpleasant, fermented taste if present in high concentrations. 

However, in proper balance, we believe provides notes of lime and sweetness. 

The concentration of acetic acid in green coffee can increase as much as 25 percent during shorter roasting periods, but it drops off if roasting continues.  

Coffees that grow at high elevations or in mineral-rich, or volcanic soil often contain more perceived acidity. 

Further, washed coffees are more acidic than naturally processed coffees, which might be because the beans go through a natural processing process.

Coffees usually contribute more body to a cup, and the body often diminishes perceived acidity. 

Some people find that coffee is too harsh on their stomachs and causes acid reflux. 

We should note that coffee isn’t all that acidic. Regardless of the acid combination in any cup, coffee is usually around a 5 on the pH scale. 

From some perspective, pure water is a 7 (neutral), saliva is a 6, and orange juice is a 3. 

However, there is evidence that the chlorogenic acids in coffee increase acid in a coffee drinker’s stomach, which can trigger acid reflux.

According to a 2005 article in Roast magazine, as little as 200 milligrams of chlorogenic acids can increase stomach acid (in a typical cup, you’ll find between 15 and 325 milligrams). 

A few friends have shared anecdotal evidence that lighter roast coffee affects their stomachs more than darker roasts, which supports that conclusion.   

According to a 2005 article in Roast magazine, as little as 200 milligrams of chlorogenic acids can increase stomach acid (in a typical cup, you’ll find between 15 and 325 milligrams). 

A few friends have shared anecdotal evidence that lighter roast coffee affects their stomachs more than darker roasts, which supports that conclusion.

A Love Affair with Acidity

Acidity is a prized characteristic among many craft coffee professionals. It’s probably safe to say that professionals like acid-heavy coffee more than the public does.

Coffee that your barista might describe as balanced might have a zing to it you just can’t take. I like some acidity, but I think it’s a gained taste, and you shouldn’t let anyone shame you about it.

Plenty of coffees, particularly natural and those from lower elevations, have less perceived acidity. If you don’t like acidity, look for flavor notes related to chocolate, caramel, and flowers as opposed to those related to fruit, particularly citrus fruit.

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