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Why Coffee Smells Different Before and During a Sip
Explore orthonasal and retronasal coffee aroma, how saliva and taste change the experience, and a simple way to notice the difference in your own cup.
Quick Answer
Coffee aroma reaches your nose through the nostrils before a sip and from the mouth during drinking. Saliva can change aroma release, while taste and texture shape the flavor you notice.
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Your Nose Receives Aroma by Two Routes
When you smell coffee above a cup, aroma molecules enter through your nostrils. This is orthonasal smelling. During drinking, aroma can travel from your mouth through the passage behind it toward the nasal cavity. That route is retronasal smelling.
The US National Institute on Deafness and Other Communication Disorders describes both routes reaching sensory cells high inside the nose. Retronasal aroma is still smell, even when it feels as though it belongs in your mouth. During a sip, it combines with basic tastes such as bitterness and the coffee's texture to make up the flavor experience.
Try a Two-Moment Observation with One Cup
Use one cup prepared the way you enjoy it, keeping the ingredients the same between smelling and sipping. Let it reach a comfortable drinking temperature. Smell gently, take your usual sip, swallow normally and breathe naturally.
Give the smell, the sip and the finish their own short lines. An example note could be:
- Before the sip: nutty aroma.
- During the sip: a more roasted aroma, with noticeable bitterness.
- Finish: bitterness lingers after the aroma fades.
Use your own words, including "hard to name" or "no clear difference." If you compare notes with someone, ask which moment each of you means. For preparing and comparing several coffees, use the at-home tasting guide.
A personal note: I would enjoy sharing this small exercise with someone who describes coffee differently from me. One of us might notice a nutty aroma while the other is thinking about the bitter finish. Before trying to agree on a word, I would want to know which moment each of us meant. That feels like a more welcoming conversation than searching for a correct answer. I would be happy with a simple description if it helped me understand the other person’s cup, and made us both curious enough to take another sip.
A Sip Changes the Conditions Around the Aroma
Above the cup, you smell the air over the liquid. In your mouth, coffee spreads, mixes with saliva and contacts oral surfaces. Aroma compounds divide between the liquid and air in different ways, so changing that mixture can change what becomes available to smell.
In Genovese and colleagues' 2014 study, a retronasal aroma simulator examined coffee with human saliva and different sip volumes. Saliva and the amount of coffee changed the release of particular volatile compounds, with effects differing across brews and compounds. This measured release in a simulator, rather than a person's whole flavor experience.
The Same Aroma Can Feel Different Beside a Taste
Flavor also depends on how taste and aroma are experienced together. A change in perception does not always mean more or fewer aroma molecules were released.
In Paravisini and colleagues' 2019 experiment, an eight-person trained panel assessed prepared mixtures of coffee aroma and bitter compounds. Their retronasal aroma ratings changed, while a separate smelling task found no significant orthonasal difference and instrumental analysis found little change in the aroma composition of the air above the mixtures. The findings supported perceptual integration of taste and aroma.
That is why the nutty smell and bitter finish in the example can both be useful observations. The smell describes an aroma association; the finish also includes a basic taste. One does not cancel the other.
Milk Adds Another Change to the Comparison
If you smell black coffee and then sip it after adding milk, you have changed the drink as well as the route of smelling. Record that ingredient change as part of the comparison. For the simple sniff-and-sip observation, keep the same drink in the cup for both moments.
Sources
- NIDCD, Smell Disorders: How does your sense of smell work?
- Genovese et al. (2014), Effect of human saliva and sip volume of coffee brews on the release of key volatile compounds by a retronasal aroma simulator
- Paravisini et al. (2019), Impact of bitter tastant sub-qualities on retronasal coffee aroma perception
- Itobe, Nishimura and Kumazawa (2015), Influence of Milk on Aroma Release and Aroma Perception during Consumption of Coffee Beverages. Three panelists supplied in-mouth aroma samples; a separate sensory assessment involved 31 trained panelists. Most measured odorants did not differ significantly between the milk- and water-diluted coffees, while several were lower with milk.
- Cleve et al. (2025), Effects of Roasting Level and Milk Addition on In Vivo Aroma Release and Perception of Coffee. Thirteen participants evaluated medium- and dark-roasted coffee with cow milk, oat milk or water making up 30% of the drink by weight. Perceived flavor changed without systematic suppression of the measured coffee-related aroma release.