Making a meal of food experiments

Published on Thursday 12 November 2009 08:34

THE cold clouds of nitrogen spill over the edge of the table as Dr Helen Maynard-Casely beats her mixture of cream, milk and sugar, her hands clad in a huge pair of blue safety gloves.

"Give it another couple of glugs," she says to accomplice Dr Jenny Rodgers, who is holding a thermos flask of liquid nitrogen as casually as if it were a pint of milk.

There is a fresh burst of sizzling and hissing as the nitrogen hits the mixture and cools it. Helen stirs furiously again and explains: "It's literally the same gas that's in the air, but it's -170c. It's pretty dangerous stuff."

Heston Blumenthal is not the only one who likes his dinner party food to have somewhat unusual ingredients, it would seem.

Helen and Jenny are part of the 30-strong team working at the University of Edinburgh's Centre for Science at Extreme Conditions. By day they invent new materials and experiment with existing ones. And on Thursday night they will repeat this culinary feat, rustling up a bowl of instant ice-cream as part of a special "Extreme Dining" event.

They hope to excite non- scientists, and especially the young, by demonstrating and discussing some of the extraordinary things that happen to ordinary substances when you subject them to extremes of pressure or temperature.

The night will kick off with the audience tucking into an appetiser of peanuts and a discussion of how the humble snack can be turned into diamonds.

Helen explains that synthetic diamonds are created by exposing carbon to specific temperatures and pressures, mimicking what happens when the real thing is formed underground. The Swedes were the first to work out how to do it, but didn't tell anyone, so there was a classic Cold War race to perfect the technique, she says. "We'll talk about an experiment in the 1950s – it was a big race between the Americans and the Russians to make the first synthetic diamonds. The Americans were first, and then after they had completed it, they were thinking of what different carbon things they could use and peanut butter was one of them."

However, diamonds, even ones made out of burnt toast, are not that tasty so won't be on the dinner platter – but that retro classic, popping candy, will.

Jenny will hand out samples, and then explain how it works – if she can still be heard over the sound of an audience full of people popping and crackling. She says: "You use the sugar mix you'd use for normal sweets, and then you just use high pressure to put carbon dioxide into the sweet mixture, and that hardens, trapping the carbon dioxide in. When you put it in your mouth, you melt the sugar mix and the carbon dioxide comes out in your mouth."

The night is part of the Big Squeeze initiative, a public engagement project run by the Science and Technology Facilities Council. Jenny says: "Our main aim is to enthuse and engage young people about the science we're doing. This week is the Royal Society of Chemistry's Chemistry Week and their theme this year is food, so the extreme dining fitted."

The night will end with a bang thanks to Professor Colin Pulham, who specialises in working out exactly what happens when materials explode. One of his experiments involves putting a tiny amount of dynamite between diamonds and applying pressure to cause an explosion. While the diamonds will remain under lock and key on Thursday night, he will have plenty of other ways of keeping the audience awake should a full stomach lead them to drift off.

Extreme Dining might sound a little too wacky to be "proper science", but Jenny says her daily life is not quite so far from Delia Smith's as you might imagine. "I work using a really large press. I squeeze and heat different chemicals to try and make new materials and it occurred to me it's a bit like cooking, but under extreme conditions – I use higher temperatures and pressures, but I follow a method, which is like a recipe – it's basically the same kind of thing."

But her efforts result in more than just a delightful souffle, she adds: "I make new materials, so for example, I make superconductors, which are conductors that, when you pass a current through them, there's no resistance. So if you could create them at room temperature, you could create wires that conduct electricity without losing heat.

"I try and discover new materials, so sometimes I don't know what the applications are going to be when I start. I mix together different chemicals and see what they make and measure their properties. It's exciting."

By contrast, Helen uses everyday materials, but tries to work out how they would behave in far-flung corners of the solar system, where the atmospheric pressure is very different. "I don't tend to look for new materials, I take pre-existing, fundamental materials like water and methane and compress them, and they form very different crystal structures which have different properties. Ice is a great example. There are 18 different forms of ice created with different types of temperature and pressure. Out in the outer solar system, most of the planets beyond Jupiter and their moons are big balls of rock and ice, and if you can understand what happens under pressure, you can understand what happens there."

So while Heston Blumenthal might get the credit for creating crazy culinary concoctions, these are the people who do the groundwork that makes them possible.

And the pair clearly enjoy showing off the lighter side of their work. As the ice cream demonstration concludes, Jenny recaps, a la Delia: "So, we've got a mixture of double cream, whole milk and some sugar, vanilla chocolate chips. And a flask of liquid nitrogen . . ."

". . . which is surprisingly cheap, if you know where to get it from," adds Helen (in case you're wondering, it's only available from reputable chemistry labs).

The outcome is delicious – a soft, cold, creamy dish which would be at home on the table at any dinner party. And, let's face it, there can be no better way to convince people that science is fun than a great big cloud of sizzling steam and a nice plate of pudding.

Extreme Dining is a free public lecture held at the Centre for Science in Extreme Conditions, King's Buildings, at 7pm tonight. Visit www.csec.ed.ac.uk.