Sour Vs. Bitter Coffee (Why Does It Taste Like This)

Last Updated on May 3, 2022 by John Moretti

Coffee can be complicated. There are several varieties of types of coffee. The coffee bean is grown in various regions of the world, and there are many ways to brew coffee. All of these factors contribute to the way a cup of coffee tastes. Two of the most prominent flavors that are experienced when drinking coffee is sourness and bitterness, but what makes these flavors occur?

Coffee can be sour due to under-extraction or natural acidity. Natural acidity can be pleasant, but the over-extraction sourness is often confused with bitterness. Bitterness in coffee is due to over-extraction, over-roasting, or naturally bitter flavors found in some coffee species such as Robusta. 

The terms ‘sour’ and ‘bitter’ are often used to describe the way coffee tastes, but these words generally mean different things depending on the coffee. Decoding the flavor descriptors to either avoid or replicate certain flavors in coffee is key to brewing your perfect cup. Let’s explore the causes of these flavors and the differences between them in coffee. 

Sour-Bitter Confusion

Before we explore the sour and bitter flavors present in coffee, it is important to understand a phenomenon known as sour-bitter confusion. Understanding this concept will help us to better move forward with our exploration of coffee flavors. 

Sour-bitter confusion occurs in many people, and it is described as the confusion of sour and bitter sensations on the tongue. The taste receptors on the tongue that perceive sour and bitter flavors are very similar and very close together, which often leads a person to perceive a bitter flavor as sour and vice versa. 

Photo of a woman that doesn't like the taste she drank from the cup

This phenomenon makes tasting coffee very confusing, and some people will state that they do not enjoy a certain coffee due to its bitterness, but what they are actually tasting is tart acidity, but they are simply unable to identify the flavor properly. 

The same is true for sour flavors, as they are often mistakenly perceived as bitterness. This problem is common and confusing, but with practice, it can be overcome. 

However, sour-bitter confusion is why many coffee drinkers do not understand the differences between sour coffee and bitter coffee. Understanding how to identify these two flavors will help to highlight the differences between them. 

Let’s take the time to explore the differences between sour flavors and bitter flavors by first identifying the four main causes of sour and bitter flavors in coffee, especially those that generally lead to sour-bitter confusion. 

Sour Coffee Flavors

a close photo of a coffee

Coffee may be described as tasting sour for two main reasons: the can may be under-extracted, meaning that the coffee was not brewed well enough to extract all of the soluble material and flavors from the coffee beans or the coffee has a naturally high level of acidity. 

Both of these sour flavors are common in coffee, but the sourness that results from under-extraction is usually the culprit of sour-bitter confusion. Let’s explore at both of the sour flavors found in coffee. 


Under-extraction occurs in coffee for several reasons.

  • There may not be enough volume of water in the brew to allow all of the soluble material from the coffee to dissolve
  • the water may have been in contact with the coffee for too short a time
  • the water may not have been hot enough to properly extract the coffee
  • or the coffee may be ground to coarsely to properly extract within the brew time. 

All of these factors lead to under-extraction, which results in an under-developed, hollow, somewhat sour-tasting brew. 

The taste of under-extraction is often described as sour, but it is not the type of sour that may be found in something like citrus fruit. It is more like an empty, lackluster taste that is vaguely tart. 

This type of sourness is very similar to bitterness and is the most common source of sour-bitter confusion. 

Acidity In Coffee

photo of lightly roasted coffee beans

The other type of sourness present in some types of coffee is due to the acidity in the coffee. This is not an acidity that is harmful in any way, but it is a leftover flavor component from the coffee cherry from which the coffee bean is extracted. 

Acidity is commonly present in light roasted coffee beans, as these beans have not been roasted enough to remove all of the natural coffee cherry flavors from the beans. 

This type of acidity is more truly sour than the sourness of under-extracted coffee. The acidic sour of lightly roasted coffee is similar to that of apples or citrus fruit. This is a fresh, bright flavor that is caused by the natural flavors of the coffee cherry. 

Bitter Coffee Flavors

Bitter flavors in coffee are present for three general reasons: the coffee may be over-extracted, the coffee just may be naturally bitter because of the type of coffee bean used, or the coffee may be roasted very dark. 

All of these factors contribute to how bitter coffee tastes. Let’s explore them all a little deeper. 


Photo showing finely grounded dark coffee with sone dark roasted coffee beans in red cup

When coffee is over-extracted, it means that too much soluble material has been dissolved into the brew water. This is only a real problem with very dark roasted coffee beans or very finely ground coffee beans

When over-extraction occurs, the naturally woody and bitter flavors of the roasted coffee beans are pulled into the water along with the rich, delicious flavors, as the actual coffee bean itself begins to disintegrate and separate out into the water. 

These flavors are unpleasant and bitter, but they also lead to sour-bitter confusion because they are a naturally bitter flavor that can sometimes be misidentified as natural acidity. 

Natural Bitter Flavors

Photo of robusta coffee beans and coffee in cup

Some coffee tastes bitter simply because that is the way it tastes. Certain species of coffee, such as the Robusta variant, naturally taste very intense, earthy, and very bitter. 

A cup of Robusta coffee will taste very bitter regardless of how you brew it, especially when compared to less bitter coffee strains such as Arabica. 

Bitterness From Roast Level

Photo of dark roasted coffee in cup

If coffee beans are roasted to a very dark level, a lot of the coffee bean has become brittle, unstable, and partially turned to ash during the roasting process. 

These fragile sections of the coffee bean will be dissolved into the water when the coffee is brewed, which results in bitter, ashy, earthy, and woody flavors in the brew. Dark roasted coffee is generally associated with bitter flavors for this reason. 


Sour flavors and bitter flavors in coffee are often confused with one another but earning to identify them can help you learn what you enjoy and what you dislike in a cup of coffee. Sour coffee can be pleasantly acidic or under-extracted, and bitter coffee can be over-roasted, over-extracted, or naturally bitter due to the coffee species. 

Take the time to taste various coffees and types of coffee better understand and identify what you enjoy from a cup of coffee, and you will never find yourself tasting flavors that you don’t enjoy again!