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At cruising altitude humidity levels in the cabin are kept low, drying out the nose. As a result, the taste buds shift into low gear (taste and smell are inextricably linked). Image Credit: Supplied

Dubai: Here’s a tip for those of you who want to get your taste buds off to a flying start at 10,000 metres. Ask for tomato juice. Why? Because up in the air, this liquid tastes far less acidic and more round and perhaps even a touch sweet? The reason?

As the plane ascends, the change in air pressure curbs about a third of the taste buds from doing their job. At cruising altitude, 10,000 metres or so, humidity levels in the cabin are kept low, drying out the nose, and as a result, the taste buds shift into low gear (taste and smell are inextricably linked). The saltiness of the tomato juice feels less so.

In 2010, Lufthansa commissioned a study on in-flight food and taste perceptions. Conducted by the Fraunhofer Institute for Building Physics based in Germany, the findings, ten years on, are still worthy of being mulled as you tuck into your next on-board meal. In an exclusive interview with Gulf News, a spokesperson for Lufthansa shares the study’s findings.

“In [high altitude] conditions, the taste nerves become less sensitive and perceive less, as though suffering from a cold. Based on this, certain products are preferred less than others for consumption on board because the taste is not completely fulfilled,” says the airline representative.

Not so sweet sensation

According to James Griffith, Vice President, Culinary, Emirates Flight Catering, that provides 225,000 meals a day for over 100 international airlines, “Flavour is a combination of one’s taste buds and sense of smell, and these two are the first to be affected at 20,000 feet up. Our perception of saltiness and sweetness drop when we are inside a pressurised cabin for a period of time. The lack of humidity, lower air pressure and background noise all contribute to passengers’ sensory feelings,” he says.

Flavour is a combination of one’s taste buds and sense of smell, and these two are the first to be affected at 20,000 feet up.

- James Griffith | Vice-President, Culinary, Emirates Flight Catering

According to Lufthansa, “The air pressure in the cabin of an aircraft flying at a cruising altitude of around 10,000 metres is equivalent to being at a height of 3,000 metres. Low humidity and vibrations are additional factors to be taken into account.”

Back to the tomato juice

While the normally tart tomato juice develops a more rounder edge and coffee too suffers no great loss of taste at 35,000 feet — in fact, it retains its flavour and aroma pretty much intact — not all foods enjoy this privilege and that’s where science comes to the rescue of in-flight catering.

Chilli, cardamom and cinnamon: on their best behaviour

The Lufthansa study, which it says was designed “to produce findings that are reproducible and useful for optimising in-flight menus” found that certain ingredients translate easily from the ground to the air.

Warm spices like cinnamon, cardamom, and chili showed no difference on the ground and in the air. Umami-rich ingredients like soy sauce fared well, too.

“The test consisted of all types of processed food,” says the Lufthansa spokesperson. “It began with simple tests on individual components like potatoes, ragouts and then moved on to sauces and desserts. In the second phase, combinations of food components were tested together with all kinds of herbs including fresh and dry variations. Furthermore, liquids were tested including dressings (vinaigrettes) and coffee.”

Conclusions: Food for thought

First off, the Fraunhofer-tests demonstrated scientifically that taste and odour thresholds increase under the ambient low pressure in the aircraft cabin. “Low pressure also reduces the sense of smell but coffee was actually one of the items that was still perceived to have an intensive smell on board. Furthermore, within desserts, sugar is also an ingredient that needs to be adjusted. For example between 15 and 20 per cent [more] when serving a traditional Bavarian cream dessert.”

The spokesperson rejected the claims by some that, post-study, Lufthansa began to add more salt and sugar to its in-flight meals. “Not at all. Lufthansa did not add more salt or alternatively more sugar to any dishes in order to change the flavour,” the airline representative says.

“We actually looked into using all-natural and non-synthetic alternatives, such as tomato concentrate, orange oil, coffee oil, in order to enhance the flavour of most dishes.”

The challenge, according to the airline, is to make on-board food appeal to all. “Airline catering accordingly requires a subtle and delicate mixture of spices so that in-flight food is appealing to the taste of as many passengers as possible, since each passenger has their personal taste preferences. These preferences are additionally influenced by their regional origin.”

Take fish in white sauce, a firm favourite of in-flight meal menus, for example. The Fraunhofer study found that to revive its flagging ratings at high altitudes, the dish needed to be herbed up. But this finding is only one half of the story. The other half is the approach flight kitchens take to address the issue.

Over-compensation, as it turns out, is not the solution. “It is important to emphasise that it is actually the quantity and quality of herbs that make up a sauce and affect its taste,” says Lufthansa’s spokesperson.

“If we simply add some frozen chives, it wouldn’t turn into a delicious chive sauce. However, if we were to use freshly chopped chives and double the amount we would use for a regular recipe (on the ground), we could improve the character and flavour of the sauce.”

According to Lufthansa’s catering executive Ernst Derenthal, “Dry herbs don’t work very well. They turn into a hay flavour up there,” as he told the Washington Post.

Also, tweaks such as adding some Parmesan cheese to pasta dishes and sun-dried tomatoes to a simple green salad or to Mediterranean sauces often do the trick.

Says Griffith of Emirates Flight Catering, “Foods need to be well-seasoned but not necessarily over-seasoned. Even in a restaurant, you will have people that add salt to their dish and others that do not. If a dish seems bland on the ground, it will seem even more so in the air.”

Innately strong tastes such as the sour, bitter and the spicy are less affected by the altitude and cabin conditions, he says.

Umami, the high flyer

Another significant finding of the Fraunhofer was that the fifth taste sensation, umami, was the most unaffected by altitude. “For the most part, all flavours grouped under the umami category are used in meals served on board Lufthansa flights,” says the spokesperson.

“The flavours are used very often within the oriental cuisine and in the ‘cross-over cuisine’ category. In almost all Asian dishes such as stir-fried vegetables or stir-fried chicken, beef or seafood dishes, soy sauce is used, which enhances the umami flavour. Other examples of foods with umami flavour include stir-fried soy beef, glass noodle salads, many Chinese dishes i.e. five-spice chicken and many Thai dishes. Umami is very common in Chinese or Japanese and Thai food [too].”

Clearly, pungent and strong aromatics keep their status aloft in the air. Says Griffith, “Cardamom, lemon grass and curry are all more pungent and intense flavours that work well in the humidity setting of an aircraft. Passengers’ umami sense seems less effected and sardines, seaweed, mushrooms, tomatoes and soy sauce all hold up well.”

Though the test was done nearly a decade ago, the findings are still relevant and have helped Lufthansa optimise its in-flight menus.

“The trends are constantly changing, and passenger profiles have also adjusted over the years,” according to the spokesperson.

“The tasting tests have underpinned previous hypotheses scientifically and are to be utilised in airline catering recipes.”

TASTE SPECTRUM

Tomato juice

Among the best-behaved taste sensation at high altitudes.

Salt

Perception is reduced by between 20 and 30 per cent. (For example, when boiling potatoes or pasta or blanching fresh vegetables, extra salt is added to make them “fit for on board consumption”, as it is called.)

Table sugar

Perception of fruit’s real taste and [sweetness of] table sugar is reduced by between 15 and 20 per cent.

Herbs

Aromas of herbs also diminish. In contrast, the taste threshold of acids remains the same.

Cardamom, lemon grass, curry flavours, these maintain their profile at higher altitude.

Cuisines

Some types of cuisines fare better up in the air. Middle Eastern and Asian cuisines, for example, with their liberal use of spices and roots have a stronger “flavour profile” as they encompass the umami flavour.

Western and Middle European cuisines have a comparatively lesser flavour profile.

Cream soups and sauces

Salt is added to almost all-Western cream soups or sauces (except for tomato-based sauces like Marinara or basil pesto sauces).

Proteins in a sauce reheat well due to the moisture.

Umami

All flavours in this fifth taste sensation band-width hold up well. Soy sauce, seaweed, mushrooms of most kinds, green tea and vegetables such as carrots, peas, broccoli, ginger, tomato and sun-dried tomato, to name some ingredients.