Wine in GTR: Drinking at 35,000 ft

Jamie Goode explains the science behind the way aircraft passengers experience scent and flavour


MOST ARTICLES LOOKING at the way air travel changes our senses of taste and smell focus on physiology. But perhaps we should also consider the way our minds work? There’s something about airports and flying that affects our psychology. Airports are usually busy, bustling places – places where we are waiting for something to happen, and also, if we are unlucky, places where we spend a lot of time queuing. They are also places where status is immediately obvious. If you have it, you queue less, you get to use private lounges and you get on the plane first.

But more than this, airports are places from where people are going somewhere. They are on a journey, whether it is for leisure or business, or even starting a new life abroad. There’s something about this transition point and the act of journeying that seems to change people’s psychology. It also seems to make them shed some of their normal inhibitions when it comes to spending – many people feel a need to open their wallets to buy food and drink.

Travellers also represent a captive audience, especially when there are delays involved. For this reason, there’s a lot of money in travel retail. Although figures are hard to come by, Heathrow makes around £400m a year on concession rental. Typically, retailers in airports will pay a percentage of their profits rather than a fixed rent, with the cut around 10-15%, depending on the airport. High-end and luxury brands seem to dominate the retail space.

But this article is focusing on what happens with regards to the perception of food and, particularly, drink in the air. This is where the airport psychology effect needs to be considered, too. Most articles on the topic seem to look merely at the effects of the cabin environment on taste and smell physiology, but we are increasingly becoming aware of the effect that psychology has on perception. For a more complete understanding of flavour in the air, this should be borne in mind.


Inside an aeroplane the air is dry and there’s not very much of it, and it is noisy. These elements all work together to alter our perception of food and drink.

Aircraft fly high to reduce cost. At 35,000ft (10,700m) the air is thinner and there’s less resistance, although there’s still enough to create lift to keep the plane in the sky. But people can’t survive at this altitude, because there’s not enough air to breathe, and it’s freezing cold. So air has to be brought in from outside and the cabin pressurised.

This is where the compromises start. As the air comes in from the engine compressors, it is hot and at high pressure. It is cooled and expanded, and mixed with the recirculated air from the cabin. Just enough air is brought in to keep things OK, but not too much. As planes don’t have humidifiers, the air humidity level is all to do with the recirculation rate. The fuselage skin is thin and very cold, while the plane air is much warmer. So if the humidity level is kept higher for the sake of comfort, there would be big problems with condensation.

And cabin pressure is kept lower than on the ground. The pressure at 35,000 feet is 24.8kPa – kilopascal, a measure of pressure. 24.8 kPa is 3.6 pounds per square inch [psi]), but this is typically raised to the pressure found at 8,000 feet, which is 75.8kPa (11 psi). At this level, the pressure on the doors is around 4.3 tons. If the pressure were to be raised to what we are used to at sea level – one atmosphere, which is 101kPa or 14.5psi – then the pressure on the door would be 6.4 tons. This would also cause problems with metal fatigue on the vast number of aircraft which have metal hulls.

The newest aircraft, the Airbus A350 and Boeing 787 Dreamliner, have new composite hulls made of carbon fibre, so there is less of an issue with humidity and the cabins can be run at higher pressures. Raising the pressure to the equivalent of 6,000ft (9.06psi) brings with it noticeable improvements to the cabin environment, but apparently there is little to be gained by raising it further. Concorde used to have cabin pressure raised to this level when it was flying.

The other factor that can affect the cabin environment is noise. Although we tend to filter it out, it’s noisy inside an aeroplane – usually around 85 decibels – and this background noise can have a significant effect on perception.

One factor rarely considered in these discussions is the fact that, when we fly, our body clocks are often out of synch. Even if you have only just left the time zone your body is operating on, you will frequently be served food and drink during the flight that won’t correspond with normal meal times. And our bodies don’t just operate a circadian (24-hour) cycle. Instead there are lots of different hormonal and physiological cycles operating that can affect our perception as well as our mental state, and these are being disrupted during a long-haul flight across several time zones. Olfaction is known to be affected by circadian rhythms, so it follows that flavour perception will be too. You can’t cheat chronobiology.


What is the science of altered flavour perception in aircraft cabins? We all bring a lot to each wine tasting. There’s our previous experience of wine; there’s our expectation — and even our mood. These feed into the complex processing that takes place in our brains to construct the conscious experience of flavour. The lower humidity and pressure in the air changes the way the olfactory receptors at the back of our noses interact with smell molecules. The transport of these smell molecules to the receptors that pick them up in the back of our noses is reduced because of the lowered air flow, much as happens when we have a cold or an allergy. This reduces our ability to smell. The same effect has been noted at altitude by climbers.

Because what we think of as taste is strongly connected to smell, we’re likely to experience airline food and drink as less intense. The drying out of our noses and throats likely exaggerates this effect. But could the real story be more nuanced and interesting than simply a diminished experience of food and drink in the air?

Scientists at a research facility in Germany have been investigating this directly and are working with German airline Lufthansa to improve the in-flight experience. The Fraunhofer Test Flight Facility near Munich consists of a 52ft section of a wide-body Airbus A310-200 suspended inside a low-pressure chamber. Lufthansa’s researchers have used it at least six times in attempts to fine-tune the airline’s food and drink offerings. This test facility has also been used to analyse the effects of flying on our perception of flavour overall, at a more theoretical level. Back in 2008, Florian Mayer and his colleagues compared the responses to a range of odours, tastes, and six different wines at normal pressure (95kPa) and simulated flight conditions (76kPa, low humidity, plus some added vibration and noise).

First, they looked at detection thresholds for a range of odours. This is done with triangle tests. Three samples are provided, of which two are different (the two could be the control, or the experimental sample). If you can spot the odd one out, you are successfully detecting the odour or taste. Then, its concentration is gradually reduced until you can’t. Using this technique, the scientists demonstrated reduced thresholds for odour detection in the simulated cabin environment. That’s to be expected. But what is particularly interesting is that not all smells and tastes were equally affected. Fruity-smelling esters were perceived as much less intense in ‘the air’, whereas vanilla-like lactone aromas were far less affected. Most significantly, the perceived intensity of sweet and salty flavours fell by as much as 30%.

When it came to comparing wines, the researchers did the experiment with highly rated examples of red and white, but also put in cheap supermarket wines. The preferences didn’t change — people still preferred the more expensive wines in ‘the air’ — but overall the wines tasted less fruity and thinner, so lighter-style wines suffered more than big, bold, full-flavoured ones.

It’s not just pressure and humidity that are different in the air. There’s also the background noise from the engines. It is becoming clear that noise affects the way we perceive flavour. A study in 2011 showed that loud white noise significantly reduced the experience of sweetness and saltiness. The background noise in flight averages 85 decibels and, as with altitude and cabin pressure, that degree of sound doesn’t affect all flavours equally. Psychologist Professor Charles Spence at the University of Oxford and his colleagues have shown that

They have pointed out that the taste of umami is unaffected (and even enhanced) by background noise. They speculate that this is why, in the air, people love ordering tomato juice and Bloody Marys, even if they never do on the ground. Spence speculates that airline passengers might have worked out by trial and error what scientists have only recently figured out – rich in umami, tomato juice tastes better with background noise than it does without, and umami-rich foods don’t suffer from the same altitude and humidity effects that diminish other flavours. As a result of these sorts of studies, airlines are now routinely enhancing the saltiness and sweetness of their meals, adding extra spice to offset the effects of the cabin environment.


This is where we need to bring psychology into the equation. A lot of the pleasure of drinking wine doesn’t just come from the liquid in the glass. Some people enjoy the experience of flying, with the buzz of the airport, and then the act of settling into their seat, taking off, and heading to a new destination. With this mindset, they are primed to enjoy any wine that’s poured into their glass. But for those who find flying stressful, doing anything, including drinking wine, will be less enjoyable in the air.

In economy class, the wine options will usually be limited, and wine will be reduced to a commodity – red or white. In that case, whether or not people are perceiving the wine at its best is a moot point. If they are flying business class, they may well be so happy not to be in the economy cabin they’ll appreciate anything they are poured.

If we begin to factor psychology into the equation, plus, of course, individual differences, then suddenly the matrix of any study seriously assessing wine in the sky becomes impossibly complicated. But airlines try to account for the cabin environment when they make their wine selections, at least for premium cabins.

Emirates is an airline that takes wine quite seriously. “Each wine is especially chosen to withstand the rigours of flight to ensure that the quality of wine will match the quality of the meals,” says Joost Heymeijer, senior vice president, inflight catering service delivery at Emirates Airline. “With wine selection, it’s important to be bold with flavours as at altitude the subtleties often disappear. We always look for wines with good acidity that tends to flatten when at altitude. This makes for a more balanced wine while flying, such as crisp, citrussy varieties such as Riesling and Sauvignon Blanc. We also serve wines with strong characteristics – eg full-bodied Malbec – as they often show better.’

Singapore is one of the few airlines to test its meals in a pressurised cabin. “This enables us to truly test potential dishes in a realistic environment,” says a spokesperson. “Such a dedicated cabin is very rare within the airline industry and we find it a great asset in ensuring our meals taste great in the air. Strong flavours such as curries often work well at altitude, so frequently feature in our menus.

“Beyond the cabin environment, however, we also consider the unique airline catering process when determining which dishes to serve. Some foods don’t withstand the reheating process well, so are not featured.”

For the wine selection it works with a panel of experts, including the UK’s Oz Clarke. “The cabin environment is definitely an aspect they consider when making their recommendations. Generally, wines that work best are zingy, fresh and have lots of fruit in them.’

United employs Doug Frost MS MW as its expert. “I’ll admit to some scepticism to the so-called science that has been cited by some in the airline industry when it comes to sensory differentiation in the air,” says Frost. “I have long felt that it seems odd to describe someone’s sensory equipment as somehow changing in the dry, low-pressure environment of a cabin at 35,000ft. Rather, the likely explanation would be that aromatic volatility is reduced under those humidity-pressure conditions. So my response has been to try to choose wines with greater aromatic intensity in hopes of mitigating that problematic effect.” He adds: “In short, delicacy is something I value in my glass but not when I’m on a plane.”

When Frost started with United 13 years ago, he says he was opposed to higher-alcohol wines, perhaps for obvious reasons. “I’ve softened on that stance, particularly as I’m looking for that flavour intensity. Sometimes higher-alcohol wines offer a bit more of that.” Still, there are surprises, he says: “I tasted a Santenay onboard the other day that was quite lovely and showed well. Go figure; that’s wine for you.”