Coffee Aroma: The Art Of Asking Questions

Coffee aroma is an important part of the coffee-drinking experience, and it's not just about the pleasant smell. Coffee aroma is the fragrance of brewed ground coffee when infused with hot water. It is related to coffee flavour and is responsible for all the flavour attributes other than those perceived by the tongue, such as mouthfeel, sweetness, saltiness, bitterness, and sourness. With over 800 aromatic compounds, coffee has a more complex aroma than any other beverage, including wine, which only has about 250. The aroma of coffee is fleeting and to experience it fully, it is best to buy freshly roasted coffee frequently in small amounts and grind the beans just before brewing.

How to smell coffee aromas

Coffee aroma is the fragrance of brewed ground coffee when infused with hot water. It is one of the primary coffee qualities, denoting a coffee's flavour, and is used by professional coffee tasters to judge the quality of a coffee.

Coffee aroma is perceived by two different mechanisms: nasally, by smelling the coffee through the nose, and retronasally, when the coffee is in the mouth or has been swallowed and the aromatic compounds drift up the nasal passage.

To smell coffee aromas, take the following steps:

• Take a moment to smell the coffee in your cup. Move the cup towards your face and you will naturally perceive the fragrance.
• Take a sip of coffee and, as you exhale, you will perceive the aroma for a second time.
• Take another sip of coffee, savour it, and swallow. Notice the flavours that appear as you swallow – these are the aromas rising to your retronasal passage.
• Think back to the initial smell of the coffee and try to remember the aromas. Compare them to what you are experiencing now to separate the flavours from the aromas.

Getting the Most Out of Coffee Aromas

Coffee aromas don't stick around for long. To experience coffee aromas in full, buy freshly roasted coffee frequently in small amounts and grind the beans just before you brew.

How to describe coffee aromas

Coffee aroma is the fragrance of brewed ground coffee when infused with hot water. It is one of the primary coffee qualities that denote a coffee's flavour, along with body, acidity, sweetness, bitterness and aftertaste.

There are over 800 known aromatics in coffee, with new ones being discovered regularly. A coffee's aroma is one of the main categories used by professional coffee tasters (cuppers) to judge the quality of a coffee.

The aroma may be described using the following categories:

Enzymatic Aromas

Encompassing herbal, fruity or flowery scents. Examples include:

• Citrus fruits, such as lemon or fresh apples
• Coriander seeds, cardamom or caraway
• Coffee blossoms or tea rose

Sugar Browning Aromas

These aromas are produced during the Maillard Reactions of the roasting process, when sugars are caramelised and flavours develop. Examples include:

• Vanilla, dark chocolate or butter
• Caramel, honey or hazelnut
• Roasted peanut, walnut or toast

Dry Distillation Aromas

These aromas are the product of burning plant fibres during roasting and are highly dependent on the roaster's style, goals and willingness to roast on the darker side. Examples include:

• Anise, clove or pepper
• Tobacco or smoke

External Changes/Aroma Taints

These are the aromas that are the result of low-quality or diseased coffee. Examples include:

• Bad wine or spoiled fruit
• Rubber or leather
• Straw or potato

How coffee aroma differs from fragrance

Fragrance

Fragrance is the scent of dry coffee grounds. It is the unit of smell that allows us to recognise something as coffee.

Aroma

Aroma, on the other hand, is more encompassing. It is not just the scent of brewed coffee but also its flavour and mouthfeel. Aroma is perceived nasally and retronasally. Retronasal perception occurs when the coffee is in the mouth or has been swallowed, and aromatic volatile compounds drift up into the nasal passage.

Differences in the Coffee-Drinking Experience

The fragrance of coffee grounds only provides half of the coffee-drinking experience. The aroma of a freshly brewed cup of coffee triggers our senses in a way that fragrance alone cannot.

Differences in Processing

Fragrance is processed through our noses in one way, whereas aroma is processed in two ways: nasally and retronasally.

Differences in Attributes

Some attributes of coffee are present and strong before brewing and disappear once brewed, and vice versa. For example, a stale coffee will have a musty and cardboard-like fragrance, but once brewed, the aroma will be stronger and may be described as complex, smoky, nutty, herbal, or fruity.

Differences in the Role of Human Senses

Fragrance is processed through our noses, whereas aroma may also affect the coffee flavour characteristics/taste sensations, as human senses tend to work in concert.

Differences in the Release of Compounds

Fragrance is the scent created by the coffee's vapours and gases, which are released from the coffee beans during grinding and then inhaled as aromatic compounds through the nose, contacting the nasal membrane. Aroma, on the other hand, is the release of flavourful compounds from coffee through the air.

How coffee aroma is created

Coffee aroma is created by a complex collection of chemical compounds, specifically volatile compounds. These are organic compounds that evaporate at room temperature and pressure. As they need to be airborne to be detected by the nose, only the more modestly-sized molecules contribute to the aroma.

The aroma compounds are created as a consequence of the roasting process. The Maillard reaction, a reaction between proteins and sugars in the coffee beans, is a big contributor to the aroma. The degradation and decomposition of other compounds in the coffee beans can also produce aroma compounds. The longer the beans are roasted, the more aroma compounds are produced.

The aroma compounds in coffee are water-soluble, which is why the hot-water preparation method is an effective way of extracting the flavour.

There are over 800 distinct aroma compounds in coffee, with more being discovered regularly thanks to advances in testing equipment. Some of the compounds include:

• 2-methylpyridine, responsible for roasted notes
• Pyrazines, which can create nuttiness or a burnt smell
• Ketones, which usually provide fruity or musty notes
• Phenols, which have ashy and smoky aromas

How coffee aroma is perceived

Coffee aroma is perceived by two different mechanisms. Firstly, it can be sensed nasally, by smelling the coffee through the nose. Secondly, retronasal perception occurs when the coffee is either in the mouth or has been swallowed, and the aromatic volatile compounds drift upward into the nasal passage. This is also known as retro-olfaction.

The perception of the coffee's fragrance comes naturally by simply moving the cup toward the face. The sense of smell comes into play as we spontaneously smell the aromas rising from the crema.

The number of aromatic compounds found in coffee is over 800, and this number increases every year as analytical methods become more precise. The perception of coffee aroma depends on the concentration of the compound and its odour threshold.

Coffee aroma is closely related to coffee flavour, as it is responsible for all coffee flavour attributes other than the mouthfeel and sweet, salty, bitter, and sour taste attributes that are perceived by the tongue.

Freshly roasted coffee will have a much stronger aroma than older, stale coffee. The aroma is strongest shortly after roasting and then declines rapidly. Coffee freshness can be maintained for months if the coffee is placed in proper storage immediately after roasting.

Frequently asked questions