If your drink suddenly tastes like nothing when you have a cold, your tongue is fine. The likely culprit is retronasal smell: aroma that travels from the back of your mouth up into your nose as you swallow and breathe out. Block that route and much of what you call "flavour" is gone. Sweet, sour, salty, bitter and umami are still there, because those come from the tongue. This post covers what the sensory research actually shows, where the famous "80% of taste is smell" figure comes from and why it's shaky, and a few small serving changes you can try tonight.
What retronasal smell is (and why it feels like taste)
You smell in two directions. Orthonasal smell is sniffing: air comes in through your nostrils from the glass, the kitchen or the world. Retronasal smell runs the other way. When you swallow and exhale, aroma molecules from the liquid in your mouth travel up the back of your throat to the same smell receptors.
The odd part is where your brain puts that signal. In a brain-imaging study published in Neuron, Small, Gerber, Mak and Hummel (2005) delivered the same odours (chocolate, lavender, butanol and farnesol) through the nose and through the mouth. They note that odours perceived retronasally "are referred to the oral cavity," while sniffed odours are referred to the outside world. They also found extra activity in the mouth area of the sensory cortex during retronasal delivery, and the difference between routes depended on whether the odour was a food (chocolate). Put simply, your brain files retronasal aroma under "mouth." That is why it feels like taste.
Why flavour is smell, mostly: the 80% claim, checked
You've probably read that 75–95% of taste is really smell. Oxford psychologist Charles Spence looked into where that number comes from in a 2015 review in the journal Flavour. He found that "empirical evidence in support of such a precise-sounding quantitative claim is rarely, if ever, cited."
He traces the claim to a 1977 study by Murphy, Cain and Bartoshuk. According to Spence's account, it had just six trained panellists and one sweet-smelling odorant (ethyl butyrate) mixed with saccharin. Participants credited about 80% of the mixture's intensity to taste. Yet, as the authors are quoted, "when the nostrils were closed, as much as 80% of the 'taste' disappeared." That is striking, but it is one small experiment with one odour–taste pairing, and the stimuli may have been both sniffed and sipped.
Spence's conclusion is the honest version. An exact percentage probably can't be given, because the answer "is likely to vary quite markedly" from one food or drink to another. Even so, "most researchers would appear to agree that olfaction plays a 'dominant' role." So the useful takeaway is that aroma is the biggest part of flavour, not that it is a fixed 80%.
Aroma and taste: what each sense actually does
- Taste (gustation): sweet, sour, salty, bitter, umami. These are detected on the tongue and survive a blocked nose.
- Aroma (olfaction): everything that makes cucumber taste like cucumber and mango like mango. Most of it arrives retronasally while you drink.
- Mouthfeel and temperature: body, coolness and the warmth of alcohol. These are touch and chemical sensations, not smell.
Pinch your nose and sip something fruity. You will still get sweetness or tartness, but "lime" or "pineapple" fades into a vague, generic sensation. Let go mid-sip and the fruit flavour comes straight back. That ten-second test is the easiest way to see retronasal smell at work.
Why a blocked nose flattens taste
Congestion from a cold or allergies narrows the airway that retronasal aroma has to travel through. Less aroma reaches the receptors, so drinks seem flat even though your tongue is working normally. When the swelling goes down, flavour usually comes back with it.
Not every loss of flavour works this way. In a large international survey of 4,039 people diagnosed with COVID-19, Parma and colleagues (2020, Chemical Senses) reported average self-rated drops of about 80 points for smell, 69 points for taste and 37 points for chemesthesis (sensations like cooling or burning) on a ±100 scale. Importantly, "perceived nasal obstruction did not account for smell loss." In that case the problem seemed to be in the nerves, not a stuffy nose. If your sense of smell or taste stays reduced after a cold has cleared, see a health professional.
How serving choices change what you smell
You can't change your biology, but you can change how much aroma reaches your nose. These suggestions follow from the research above. Treat them as experiments, not guarantees.
1. Pour it into a glass
A can opening gives you very little to sniff before you sip. Pouring into a glass adds an orthonasal "preview" that sets your expectations. In a study of 181 untrained volunteers, Hummel and colleagues (2003, Appetite) found that ratings of wine odours changed with glass shape, and this "appeared not to relate to the esthetic impression the glasses made." A tulip-shaped glass that narrows at the rim is a reasonable choice.
2. Don't serve it ice-cold the whole time
Aroma depends on molecules escaping the liquid, and more volatile ones escape more easily. In an animal study, Gautam and Verhagen (2012, Journal of Neuroscience) found that retronasal responses in rats' olfactory bulbs were smaller than sniffed ones (0.23 vs 0.39 %ΔF/F). How well an odour worked retronasally tracked its volatility closely (r = 0.92, p < 0.005). Cold liquids give off fewer volatiles, so try drinking a well-chilled drink and letting the last third warm slightly. Notice whether the fruit comes forward.
3. Breathe out through your nose after you swallow
This is how to taste a drink deliberately. Take a moderate sip, hold it for a second, swallow, then exhale gently through your nose with your mouth closed. That pushes aroma along the retronasal route.
4. Taste in a neutral setting
Strong competing smells, like candles, barbecue smoke or cologne, mask subtle flavours. Compare flavours somewhere neutral, with water in between.
Caveats: what the research does not show
- Small samples, old data. The source of the 75–95% claim involved six people and one odorant. No precise percentage has been established for drinks in general.
- Brain imaging is not experience. Small et al. show different brain activity for the two routes. That doesn't tell you how much any particular drink will improve with a particular serving trick.
- Animal data. The volatility and sensitivity numbers above come from rats. Human retronasal smell may behave differently.
- Wine, not vodka water. The glass-shape study used wine. We know of no published study testing glassware with canned cocktails.
- Self-report. The COVID-19 figures are self-ratings collected early in the pandemic, not lab measurements.
- Nothing here is a health claim. Better aroma changes how a drink tastes, not what it does to you. The alcohol is the same however you serve it.
Putting it to work with a still vodka water
Aroma is a good test for a still drink. Aura is premium vodka with alkaline water (pH 8.5+) and natural flavour, with zero carbonation, no added sugar, no artificial sweeteners and no preservatives. Without bubbles there's nothing to hide behind, so the flavour has to come from aroma, which is why the exhale-through-your-nose habit is worth trying. Pour a Cucumber Lime, Coconut Pineapple or Mango Peach into a glass, try the pinch-your-nose test, and notice how much of the flavour returns when you let go. Learn more about why Aura is made as a still drink.
This article summarises published research for general interest and is not medical advice. Please enjoy responsibly and only if you are of legal drinking age in your province.
Ready to try the experiment yourself? Browse our vodka water cocktails. In Canada, Aura is available across British Columbia, Alberta and Ontario. Our direct and wholesale ordering delivers to Ontario addresses only. In BC and Alberta, find a nearby retailer through where to buy, including BC Liquor Stores, licensed private retailers in BC and AGLC-licensed private retailers in Alberta.
Sources
- Spence C. Just how much of what we taste derives from the sense of smell? Flavour. 2015;4:30. doi:10.1186/s13411-015-0040-2. https://doi.org/10.1186/s13411-015-0040-2
- Small DM, Gerber JC, Mak YE, Hummel T. Differential neural responses evoked by orthonasal versus retronasal odorant perception in humans. Neuron. 2005;47:593–605. PMID: 16102541. doi:10.1016/j.neuron.2005.07.022. https://pubmed.ncbi.nlm.nih.gov/16102541/
- Hummel T, Delwiche JF, Schmidt C, Hüttenbrink KB. Effects of the form of glasses on the perception of wine flavors: a study in untrained subjects. Appetite. 2003;41(2):197–202. PMID: 14550318. doi:10.1016/s0195-6663(03)00082-5. https://pubmed.ncbi.nlm.nih.gov/14550318/
- Gautam SH, Verhagen JV. Retronasal odor representations in the dorsal olfactory bulb of rats. Journal of Neuroscience. 2012;32(23):7949–7959. doi:10.1523/JNEUROSCI.1413-12.2012. https://pmc.ncbi.nlm.nih.gov/articles/PMC3516401/
- Parma V, Ohla K, Veldhuizen MG, et al. More than smell—COVID-19 is associated with severe impairment of smell, taste, and chemesthesis. Chemical Senses. 2020;45:609–622. PMID: 32564071. PMCID: PMC7337664. doi:10.1093/chemse/bjaa041. https://pmc.ncbi.nlm.nih.gov/articles/PMC7337664/