Rupert Parker takes a tour of the Delta kitchens at Heathrow Airport, learns that cabin pressure makes things taste differently, and samples a selection of the dishes.

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As a regular traveller, I’ve consumed many airline meals and, as a food writer, I’ve always wondered what goes on the ground before they’re loaded onto the aircraft. So, when I got an invitation to visit the kitchens of Gate Gourmet at Heathrow, I set out for the airport without my suitcase, just armed with my notepad. Gate Gourmet are a Swiss company and the world’s largest independent airline meal provider producing over 250 million meals globally. At Heathrow, during the busy summer season, they produce around 22,000 meals per day, so you get an ideal of the scale of their operation.

Delta is keen to publicise the food in their business class, known as Delta One. The meals are all produced in Gate Gourmet’s kitchens, although interestingly, the economy class meals come from another facility in Germany. They’re frozen, unlike the Delta One meals which are all prepared fresh in a cook-chill process. On my tour, I don’t get to see the cooking, as that takes place in a different facility, but get to see the meals being assembled in a huge production line. Each worker is given an IPad, with pictures showing exactly how the dish should be put together. There’s also what they call a “Golden Sample”, a real-life example in front of them so nothing is left to chance.

I talk to the Executive chefs who’re responsible for creating the meals and they tell me that people’s taste buds change in the aircraft cabin, as the pressure is only 75% of that on the ground and the air is drier. That means passengers produce less saliva so flavours have to be stronger. Their aim is to add more Umami taste, rather than add salt, using ingredients like mushroom powder or bouillons, and fortunately MSG is banned. Even wines that are perfectly acceptable on terra firma, have a different character at altitude, so tastings and selections are made in the air.

Aircraft spend an average of one and three quarter hours on the ground so, as soon they land, the carts full of dirty dishes are offloaded and brought back to the facility to be washed and any food waste disposed of. The carts containing fresh meals have already been prepared, and are kept chilled until they’re ready to go. Sometimes business passengers turn up at the last minute and request special menus and the system is flexible enough to accommodate that.

On board, the flight attendants prepare the meals. They don’t use microwaves but conventional ovens, which are heated to 160C. For hygiene reasons the dishes have to reach 75C so beef is cooked for 22 minutes, fish for 18 minutes. The chefs tell me that they need to choose a robust species like cod or monkfish and the last thing you can expect is a rare steak. Once the dishes are cooked, the flight attendants arrange everything on plates, using pictures as a reference, and then deliver them to the passengers.

After my tour, I get a chance to taste the dishes, with their accompanying wines:

• Smoked salmon and grilled shrimp with capers, chopped onion and cocktail sauce.
• Spicy Thai coconut soup.
• Caprese salad with basil infused olive oil.
• Beef tenderloin with café de Paris butter, gratin potatoes, sautéed spinach and carrots.
• Roasted cod fillet with saffron tomato sauce, parsley potatoes and broccoli.
• Roasted chicken breast with morel mushroom sauce, brown butter broccoli and egg noodles.
• Five cheese ravioli with arrabbiata sauce.
• Selection of fine cheeses with fresh fruit.
• Cheesecake and chocolate mousse brownie.
• Vanilla ice cream sundae with choice of sauce, whipped cream and chopped nuts.

It’s a bit of marathon tasting, but fortunately each dish is bite-sized so I plough gainfully on. Eating airline meals on the ground, in a restaurant setting, is a unique experience and I enjoy the enhanced flavours. The Thai soup is just the right side of spicy and the cod fillet is surprisingly good. They tell me all their beef is sourced from Argentina and I find the tenderloin as tender and as tasty as it should be. The roasted chicken is rather bland, but the cheesy ravioli more than makes up for it.

Finally I get a Lobster Slider, their signature dish – simply lobster chunks in a marie-rose sauce served in a bun, topped and tailed with lettuce and tomato with gherkin on the side. Apparently you get one of these just before landing and I can’t think of a better way to send you on your way. Mind you, if I had the chance, I would sneak back for seconds.

The Delta website has more information about travelling with their Delta One service.

Rupert Parker Rupert Parker is TV Producer, cameraman, photographer and journalist. Although his special interest is food, wine and travel, he writes about everything from wilderness adventure to gourmet spa tours. His articles appear, not only in British national newspapers and magazines, but also in magazines in China and India. Read more on his Planet Appetite website and follow him on Twitter @planetappetite