Coffee professionals and enthusiasts are always keen to find new ways to experience flavour and aroma. And there are seemingly endless ways to experiment – ranging from trying different processing methods to even changing the drinking vessel itself.

One of the most interesting – yet not widely practised – ways to manipulate how we taste coffee is aeration. Commonly used in the wine industry, aeration accelerates the oxidation process, which can dramatically change flavours and aromas.

So as the wine industry continues to influence specialty coffee, will we see more high-end coffee shops start to adopt similar techniques?

To find out, I spoke to Eldric Stuart, founder of Aesir Filters, and Eliza Grassy, co-owner of Chemex. Read on for their insight.

You may also like our article on how different cup shapes affect the flavour of coffee.

What is aeration?

The term “aerate” simply means to introduce air into a material. Some examples are:

• Soil – gardeners puncture small holes in soil so air (as well as water and nutrients) can be mixed in more easily
• Cream and eggs – bakers and chefs whisk cream and eggs to incorporate more air into them, which makes them much lighter and fluffier
• Wine – sommeliers pour wine into decanters or use aerators to expose the liquid to oxygen. This allows it to “breathe” before drinking it

Looking specifically at the latter, there are a number of reasons why sommeliers and consumers would choose to aerate wine. 

Many wines (especially reds) are high in tannins. These are bitter and astringent-tasting chemical compounds that we refer to as polyphenols. To minimise the intensity of these flavour attributes and create a more rounded and balanced sensory profile, wine should be left to “breathe”. This can be done by simply opening or uncorking the bottle and leaving it for between 30 minutes and two hours.

Some wines, however, may benefit from even more aeration to allow more subtle and delicate flavours to come through. There are three main ways to aerate wine:

• Pouring into a glass – this process inherently incorporates air into the liquid. Sommeliers and wine drinkers will often swirl their glasses after pouring, too
• Decanters – a glass vessel with a small neck and wide base which is designed to hold wine and other liquids. After pouring wine into a decanter, a sommelier will swirl the vessel to incorporate as much air into the liquid as possible
• Aerators – a small device which fits into the neck of a wine bottle. As the wine is poured, it passes through a chamber so air is forced into the liquid. You will often hear a distinctive “whooshing” sound when using an aerator

So what about aerating coffee?

The practice of aeration in the wine industry is much more widespread than in specialty coffee. There is, however, a common method used in the coffee industry that relies on aeration to improve sensory perception: cupping.

During cuppings, many people will “slurp” coffee. This not only spreads coffee all over the tongue, but also incorporates air into the liquid – meaning Q graders and other coffee professionals can quickly and efficiently assess flavour profiles and quality.

Filter coffee can also be aerated in similar ways to wine to change its flavour profiles.

Eldric Stuart is the founder of Aesir Filters – a premium AeroPress paper filter brand used by many World AeroPress Championship competitors. He is also the founder of Harken Coffee and Aubade Coffee in Vancouver BC, Canada.

“I first started playing around with aeration about ten years ago after learning about it from James Hoffman,” he tells me. “James didn’t go into a lot of detail or explanation about why aeration changes our taste perception of coffee – it was more of an interesting commentary.

“At both Harken and Aubade, I would use a wine aerator because it’s tidier, faster, and a bit ‘showy’ (and always starts a conversation),” Eldric adds. “But at home, I do a simple high pour so that the coffee splashes in the cup – kind of like how street vendors pour chai tea.”

How does aeration affect coffee flavour?

Aerating has yet to become a common practice in specialty coffee shops, which means there is very little research available to further our understanding of how it impacts flavour and aroma. But given its extensive use in the wine industry, it’s clear that aeration can transform a coffee’s flavour profile.

Eliza Grassy is a co-owner of Chemex – an iconic manual coffee brewer. The company launched the ChemAer in early 2023, which was developed in collaboration with Trendglas and four-time Hungarian Barista Champion Attila Molnár. The ChemAer includes built-in aerator paddles, which the user activates by swirling coffee against the sides of the brewer. 

“Aeration creates a well-rounded and creamier mouthfeel,” she says. “Additionally, by swirling brewed coffee against the paddles set into the sides of the ChemAer, you force more oxygen into the liquid, which also cools the temperature of the coffee.”

Eldric explains that aeration can also minimise the impact of less desirable flavours.

“By reducing the amount of less desirable compounds, more of the subtle and delicate flavour notes can shine,” he says.

However, he adds that not all consumers may be able to pick up on the more nuanced differences.

“Does aeration work? As with anything, it’s subjective as some people may not notice any difference, but most people do, even if they can’t describe it,” Eldric explains. “In a blind taste test, almost anyone would be able to notice that coffee tastes different after aeration. 

“But does aeration make coffee taste better? Again, some people enjoy the results, but for others, it doesn’t fit what they are looking for from their coffee,” he adds.

Best practices for aerating coffee

There are several easy ways to aerate coffee, with each method having its own impact on flavour, aroma, and mouthfeel.

Stirring or swirling espresso and filter coffee is one of the most straightforward techniques, as well as pouring coffee from one vessel to another – ideally from a significant height to incorporate more air.

Wine aerators are another simple option, and are likely to achieve the most notable results.

“You can aerate coffee multiple times, but I don’t know if there is a limit,” Eldric says. “Another factor I have noticed, but haven’t tested properly, is how aeration can decrease the presence of carbon dioxide. 

“I have experienced a direct correlation between the amount of carbon dioxide in coffee (usually because it’s too fresh) and a drier mouthfeel,” he adds. “Although I believe you should leave roasted coffee to sufficiently rest to help mitigate this issue, I have found that aeration can make the texture ‘sharper’ and more defined.

“Too much carbon dioxide can obscure the taste of coffee, especially the more delicate flavours,” Eldric adds. “By reducing the amount of carbon dioxide, you can make the flavours pop.”

Which coffees work best?

Eliza offers some general guidance on how to aerate coffee.

“Don’t over aerate – start slow and experiment by swirling your brewed coffee for longer periods of time,” she says. “It may take more than one attempt to achieve the right level of aeration for a particular coffee.

“Moreover, you can aerate all kinds of coffee,” she adds.

Eldric, meanwhile, suggests experimenting with certain types of coffee.

“I find you often sacrifice some heaviness in the body when you aerate coffee (which makes it feel more airy or light), which isn’t what everyone likes,” he says. “In my experience, you can get the best results using fuller-bodied coffees that can spare some of their heaviness for more clarity and brightness. 

“If the mouthfeel of a coffee is already quite light, aerating it may not produce the best results, unless that’s the style of coffee you like,” he adds. “As always, do what tastes best to you.”

As a common practice in the wine industry, it wouldn’t be surprising to see more high-end coffee shops start to use aeration – and allow their customers to experience coffee in different ways.

Ultimately, experimenting is key. And with consumers becoming increasingly interested in novel brewing techniques, aeration could be a unique selling point.

Enjoyed this? Then read our article on whether drinking coffee from a wine glass changes its flavour.

Perfect Daily Grind

Photo credits: Chemex

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