Finally, beer may start tasting good at 30,000 feet. Airlines, which usually get a bad rap for bad food and so-so drinks, are starting in earnest to plug the sensory gap.
They are aided by the knowledge that noise, low pressure, dry air, plastic cutlery and cups are also largely to blame for meals that taste less than appetising. Studies have shown that those factors alter the way we taste things at high altitude compared to when we're on the ground.
On Wednesday, Cathay Pacific, the Hong Kong carrier, introduced on some flights a beer brewed to taste good while the flier is miles above the earth. It contains honey and "dragon eye" (also known as longan).
"We know that when you fly, your sense of taste changes," Julian Lyden, marketing manager at Cathay Pacific, said in an interview. "Airlines address this for food in certain ways."
For example, background noise on the plane suppresses sweet and salty taste, said Charles Spence, a professor of experimental psychology at Oxford University who advises airlines on food and is set to publish a book on "gastrophysics" this month.
Our sensitivity to sweet and salty foods drops by about 30 per cent in the air, compared to when we're on the ground, according to a 2010 study commissioned by Lufthansa and conducted by the Fraunhofer Institute for Building Physics in Germany.
Plastic cutlery and cups are also largely to blame when your food and drinks don't taste as good while you're flying. Photo: Supplied
At high altitudes, only umami (the pleasant, savoury "fifth" taste beloved by Japanese chefs) is enhanced for reasons that are not entirely clear. So bloody marys, which contain the umami-rich tomato and Worcestershire sauce, taste better in the sky than on the ground. It's the most consumed cocktail on passenger flights, airlines say.
Speculating about the reason for the umami appetite, Spence theorised that noise on the plane, even at 80-85 decibels ("quieter than in a New York restaurant"), raises an ancestral fear.
When faced with predators or during stressful situations, our ancestors may have turned to umami, which prompts dollops of saliva, "in order to get the energy to fight or flight," he said. (British Airways overhauled its menu in 2013 to incorporate more umami-rich foods.)
In addition to white noise, low humidity and low pressure affect the way and the order in which molecules travel to our senses, said Peter Barham of the University of Bristol, another expert on the science of taste. At 30,000 feet, cabin air is drier than the air in most deserts. That impairs our sense of smell, from which most of our taste is derived.
So when passengers savour a beer in the air, it's because the environment affects "the way the brain interprets the signals," Barham said, "so that changes the flavour of your beer."
Some airlines have experimented with what Spence called "sonic seasoning," like playing tinkling music or offering plates and glasses that make that sound, because it brings out the sweetness in meals.
Some wines fare better than others, he noted, particularly those from countries like Chile, where grapes are grown and blended at high altitudes.
Champagne, meanwhile, is probably best avoided while flying, some food experts say, even if airlines lavish high-end passengers with Dom Perignon or Krug Grande Cuvee. An experiment by champagne producer Taittinger in 2010 showed that the aroma lessens with altitude and that bubbles stick to the sides of the glass instead of giving a steady stream of finer bubbles, considered an indicator of quality champagne.
Although airlines like to lavish high-end passengers with champagne it is a drink probably best avoided. Photo: Supplied
Mikkel Borg Bjergso was the first to brew beer specifically for an airline. Since 2014, his company, Mikkeller, based in Copenhagen, has crafted 10 beers for Norwegian airline SAS. He is expected to roll out six new ones this year from his brewery outside Ghent in Belgium. The airline has gone through about two million of his bottled and canned beers.
"It's becoming a trend because there is big competition on customer experience," Bjergso said, adding that he has been approached by another airline. "SAS is spending a lot of energy on food and beverage," he said, including special apple juice produced on a small farm in Norway.
After several experiments, including tasting 25 types of beer at 30,000 feet, Bjergso concluded that more dominant flavours, like bitterness, stood out.
Beer is usually made with oats and wheat, he said, but "we just use malt, pretty much" in his airline beer. "You also add less hops at the beginning of the brewing process, to lower the bitterness."
Beer also tends to foam more because of the difference in air pressure, he said, so carbon dioxide is taken out and put into champagne bottles, which can resist air pressure better than normal bottles.
"Imagine your favourite meal – it tastes great," Barham said. "But if it's served in a plastic container and you're squashed elbow to elbow between two people, it doesn't taste so good."
New York Times