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Published, Jun 13, 2023

Sensory Series 03: Coffee Bitterness Explained

Next up in our sensory series, we’re exploring the world of bitterness. Bitterness is often met with reservation, a negative word with unpleasant associations. And yet popular food and drink items such as dark chocolate and speciality beer are revered and enjoyed for a level of bitterness.

Bitterness in Coffee

In coffee, too, bitterness plays an important and enjoyable part in the perception of flavour. Read on to discover what bitterness means in your cup, and why some coffees are more bitter than others, to be celebrated and enjoyed instead of avoided.


It’s not just taste that creates an experience of bitterness (smell, among other attributes plays a part, too), but that’s what we’ll focus on here.

The definition of bitterness isn’t much of a sell into the world of flavour and taste. As far as dictionary definitions go, the “sharpness of taste; lack of sweetness” sums it up perfectly. Stemming from Old English, ‘biter’, the word conjures up the familiarity of that sharp bite. Bitterness is neither salty nor sour, yet it can accompany these flavour sensations. As one of our five primary tastes, bitterness is one of the most sensitive; bitterness balances out umami (savoury), much as sourness helps to neutralise fattiness. While sometimes disagreeable, bitterness helps cleanse our palates and serves our taste receptors well.

Bitter cocktail


Scientists believe that our sensitivity to bitterness developed as a survival mechanism—a signal warning to prevent consumption of potentially poisonous foods (almost all toxic plants are bitter), which is why even just a little bit of bitterness is easily detectable and can have a big impact on our palate.

Although bitterness often gets a bad rep, it can be used to create well rounded and desirable flavour palates, a critical component of building intensity and complexity of flavour.


Bitterness is something that, if just right, can beautifully benefit your cup of coffee.

Green coffee vs roasted coffee

Bitterness in coffee is often thought to be a result of poor roasting, stale beans, or over-extraction. Yet bitterness is a natural component of coffee, and if coffee had no bitterness at all, you might find it to taste too acidic or sweet: the key is balance. A small amount of bitterness will help ensure complexity, complementing and adding to the fullness of other flavours without being overwhelming.

Sensory cells on the tongue contain numerous proteins: around 35 of these react with the compounds in food substances, creating the experience of bitterness. How bitter a coffee tastes comes down to these compounds, known as phenolic compounds. Some of the most prevalent of these compounds are the chlorogenic acids, which account for up to 8 percent of the dry mass of green Arabica beans. These chlorogenic acids largely influence the sensory elements of coffee. There are two chlorogenic acids in particular that shape and are responsible for coffee’s bitterness: 5-caffeoylquinic acid, which is the most common within green coffee, and di-CGA. Caffeine also plays a role in bitterness, but a secondary one.


Some coffees are simply more likely to create perceived bitterness than others. Robusta is far more bitter than Arabica, possessing more chlorogenic acids and caffeine. Factors such as species and variety, the degree of maturation, and even environmental conditions and agricultural practices will all influence the composition of chlorogenic acids in green beans and the final cup.

Processing can shape bitterness in coffee too. For example, a natural process coffee will have a greater perception of sweetness, with the skin and mucilage of the cherry kept intact through drying, allowing the process of fermentation to aid a transfer of sugars from the fruit to the seed (coffee bean), lessening the detection of bitterness.

While chlorogenic acids are responsible for bitterness, they aren’t actually bitter. In roasting, these acids begin to break down into chlorogenic acid lactones and phenylindanes; these are what create the perception of bitterness.


Brewing carefully will ensure that you bring out the best in your coffee’s flavour profile, celebrating any natural bitterness, rather than bitterness caused by over-extracting the coffee. Our brew guides will ensure you find the perfect balance in your brew, whether you’re serving up an espresso, or looking for the perfect AeroPress recipe.


Keen to explore coffees with a delicious balance of bitterness and more? Shop coffee now.