Coffee and its Compounds - What is Aroma, Taste and Flavour?

We hear the words aroma, taste and flavour being used but what do they actually mean? These are categories for how the human senses perceive different chemical compounds. It is now known that roasted coffee is made up of over 800 aroma-imparting compounds and roughly 700 of these are soluble in water, meaning they contribute to flavour. By comparison, red wine has around 300 of such flavour compounds, chocolate has 200. Below we go into more detail about these categories:

Aroma

Simply put, aromas are the scents we pick up when we smell the beans, when we breathe in that comforting fragrance of freshly ground coffee and the smells we detect from the brewed cup.

Taste

Tastes are the sensations of flavour we perceive in our mouths and throat. It is generally considered that we perceive acidity in the ‘bite’ of our cheeks and outer edges of the tongue, bitterness at the back, sweetness on the tip and saltiness to the frontal sides. However, the entire tongue picks up all five tastes with specialised receptors that identify them. The reason the taste map exists is because the aforementioned regions of the tongue sometimes exhibit heightened sensitivity to a certain taste. It is not though, something to be relied upon. All five basic tastes are found in coffee and are listed below:

Sour – In coffee, sourness can be divided into different groups. We taste malic acid, which is like the crisp acidity found in apples, grapes and rhubarb; ascorbic acid, a prevalent acid in oranges; citric acid, the sharpness found in lemons and lime; acetic acid, as found in vinegar and butyric acid, a generally unpleasant taste reminiscent of rancid fruit, beer and even vomit.

Sweet – Some coffees grown at very high altitudes can be remarkably sweet, like those in Colombia and Ethiopia. Darker roasts will also present an increased perception of sweetness due to the breakdown of acidic compounds and the further caramelisation of the coffee’s natural sugars. The sweetness in coffee is perceived in the flavours of fruit, honey, sugarcane, chocolate and caramel to name a few.

Bitter – The bitterness in coffee is provided by caffeine and the breakdown of chlorogenic acids into phenylindanes. This follows that dark roasts are bitterer than lighter roasts as the darker a coffee is roasted, the more these acids break down.

Umami – The Japanese for delicious, this taste is somewhat like savoury. This can be perceived in coffee with flavours such as mushrooms, meaty flavours and salted tomatoes. Indonesian coffees exhibit quite a few of these qualities, along with other earthy flavours.

Salty – Although not nearly as prevalent as the other tastes, we’ve had quite the shock of tasting an overtly ‘salty’ Nicaraguan coffee. Thankfully it’s rare.

Mouthfeel

There are other less widely recognised tastes that can also be found in coffee. Fat is sometimes considered a taste and has the sensation like that of oil. These tastes differ to what we call mouthfeel though, in that they are sensed by nerve endings rather than taste receptors. This is the texture of the coffee and can be recognised in the ‘stickiness’ or viscosity of the drink; its astringency, which is perceived as a dryness or spikiness at the back of the throat. Coffees that are watery in texture are said to have a light body. Other words that are used to describe mouthfeel are velvety, silky, spongy, juicy, crisp and clean (absent of defects or fermented flavours).

Flavour

All of the above come together and create what we call the flavour. Aroma, taste and mouthfeel must combine for us to perceive a coffee’s flavour. For example, when we have a cold and our sense of smell is blocked, we cannot always taste that food or beverage. In fact we are tasting it, we still receive the sensations of taste but we do not have the aroma sensing ability to identify a flavour. Likewise when we smell a scent, we are not tasting it. In many cases, the scent of a coffee is different to the flavour we expect, this is because we are working on aroma only. With the aroma circling the nose and the black liquid coating the mouth and tongue, it is then we appreciate the flavour of a coffee. For a greater understanding of the flavours in coffee, have a look at the flavour wheel.

Coffee’s Compounds and Solubility

All 700 flavour compounds will not make it into every cup of coffee. Different brewing methods produce different results, which only adds to the exploratory factor of coffee. A well-made espresso shot will create a cup with more of the bean's oils and compounds than one poured through a paper filter, as with the Chemex. That is not to say the Chemex is inferior, it only accentuates the delicate flavour compounds that pass through the paper. By contrast, an espresso shot has a fuller body and more intense flavour experience. Other variables that affect the coffee’s solubility include grind, water quality and temperature, and brewing ratios.

For more information on the different ways of brewing coffee, check out our brewing guides.

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