The eccentric engineer

Napoleon is just one of the people we have to thank for the fact we can enjoy most foods whatever the season.

These days, eating at home is only marginally more troublesome than going out. Meals can be pre-prepared, preserved, sealed, packaged and delivered. All we need to do is take them home, slot them in the the microwave, and within a couple of minutes a dinner, or something roughly resembling it, is ready.

Nor are we limited in which types of convenience meals we eat. Two hundred years ago what you ate (assuming you could afford to eat), was dictated by where you lived and the season.

A modern supermarket serves all foods at just about all times of year - for your convenience. It is as though the seasons have been made to stand still. Indeed, this was the slogan of the product that started all this off.

It was in February 1809 that the Courier de L'Europe newspaper described one Nicholas Appert's latest invention as "making the seasons stand still". And it was all down to a short but forward-thinking megalomaniac.

Napoleon was a brilliant general and an astute politician, but his overwhelming desire to conquer the world had led him into a spot of bother. He needed to give his army an 'edge', and his thoughts turned to food. Fighting at that time was a strange affair as the availability of food for men and horses meant there was an 'off season' in winter when most armies packed up and went home. What Napoleon needed was a way of preserving food grown in the summer, so his troops could eat it, and keep fighting, in the winter. No one would expect that.

So he set up a competition with a 12,000 franc prize - won, in 1809, by Appert. His method was simple but effective. By boiling the food first and then sealing it in glass jars he sterilised and protected it. It would then stay fresh until the jar was open. He called his method of preserving food in glass jars 'canning'.

A year later, American Peter Durand patented a similar technique but using tin instead of glass. Nineteen years later the first tin canning factories opened in the US and the boom in preserved foods began.

Now, Durand had forgotten something and it's thanks to another American that it was solved. Durand forgot to mention how you open these cans. The standard method was using a hammer and chisel, a clumsy technique that made your food taste of tools and your tools smell of food. But this clearly didn't bother too many people as the can opener was only invented almost half a century later.

A century later still saw a big discovery by Clarence Birdseye, one of the most prolific inventors of his day. The early career of this hero of food preservation was not exactly savoury, however, as he paid his way through college by trapping rats to sell to researchers at the University of Columbia. From 1912 to 1915, he expanded his operations from vermin procure-ment to become a fully fledged fur trader in Labrador, Canada, learning along the way a great deal about his icy environment. In particular, he noted how animal carcasses, frozen in the depth of winter, survived much better than those frozen in spring or autumn, and this set him thinking. After annoying his wife by repeatedly filling all her washbasins with cabbage leaves and brine and then leaving them to freeze solid outdoors, he finally worked out what was happening: it was fast freezing.

When foods were frozen slowly, large ice crystals damaged the cell structure making the defrosted cabbage leaves less appetising. Fast freezing, however, led to the creation of tiny ice crystals, which preserved the structure of the food, and the resulting defrosted cabbage leaves were every bit as delicious as the moment they were frozen. Of course, the locals had known all about fast freezing for centuries, but Clarence was the first to apply it to the mass production of frozen foods. The rest is convenience food history, and Clarence went on to make his name and fortune freezing everything from peas to cod (but not rats, thankfully).

But there's one engineering marvel still missing - how to heat up this feast fit for a king? This brings us onto the subject of chocolate. Put chocolate in a warm place, and before long it turns from solid into liquid. This fact is every mother's distress and every dry cleaner's delight.

It was also known to Dr Percy Spencer, a scientist working at the Raytheon Corporation laboratory in the US in 1946. He was tinkering with a new device called a magnetron when he noticed the chocolate bar in his pocket had melted and ruined his shirt. Now this was very unusual - there was nothing hot around. Spencer eyed the magnetron with suspicion. He tried putting popcorn kernels near it - and sure enough they popped. The next day he put a fresh egg by it and was surprised to see the egg begin to vibrate and rattle before exploding and showering him with omelette. He had to get through a lot of washing, but was also getting the point. Microwave radiation from the magnetron was exciting the water molecules in the food and was cooking things - incredibly quickly. Spencer decided to put a magnetron in a metal box to reflect and concentrate the waves, and so the microwave oven, as well as the true convenience meal, was born. Ketchup anyone?

Winner of December's caption competition is Colin Childs, who receives a set of Moixa AA USB-rechargable batteries. His caption is: 'How her eyes lit up when she saw the Christmas tree. Then her eyebrows lit up, then her hair…'

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