planet science diner... the micro whizz oven
It sits there quietly on your kitchen work surface, helpfully heating up your leftovers and your cups of milk. But what do you really know about your microwave?
chocolate discovery
In 1945, before there were microwave ovens, there was Percy Spencer, a small bar of chocolate and a microwave beam. Percy had placed the snack in his pocket for safe keeping – unfortunately, it was in direct line of fire of the microwave beam.
Whilst most of us would assume that a pocket full of melted chocolate was the natural result of a day spent in a warm lab, Percy realised that it was the microwave beam that was to blame for his dry cleaning bill. Once he had made the connection between microwaves and cooking, there was no stopping Percy.
popcorn
Percy Spencer, inventor of the Microwave, cooked up popcorn, for his first experimental meal in his new baby, and the microwave oven was born.
radio waves
Microwaves are part of the electromagnetic spectrum just like radio waves, light waves, and ultra violet radiation. Most microwave ovens use waves with a frequency of around 2,500 megahertz because they are easily absorbed by water, fats and sugars – the main constituents of most foods. Hmmm…perhaps you shouldn’t put radios in microwaves!
vibrating molecules
Conventional ovens work by heating the air inside the oven, which in turn heats the food. As anything becomes warm, molecules start to vibrate and bang into other molecules, making them vibrate as well. These collisions spread the heat energy but it’s a relatively slow process.
Instead of heating the air, microwave ovens use microwaves to stimulate the molecules in the food causing them to vibrate directly. As microwaves can penetrate food to a depth of a few centimetres the outer layers of the food are heated directly by the waves. The interior is heated in the normal way, by the heat energy slowly spreading through the food.
Microwave ovens are much more efficient than conventional ovens because they only expend energy heating up what's going to be eaten, rather than the air surrounding the food.
hot spots
Microwaves are a very efficient way to cook, but they are not perfect. As the microwaves bounce around the compartment they can interfere constructively or destructively with each other, producing hot and cold spots. Ovens normally have a turntable and most ready meals recommend occasional stirring to ensure even cooking of the food.
steamin'
Some foods cook better than others in a microwave. Those with a high water content are effectively steamed – vegetables come out crisp and retain more of their vitamins and taste than if they are boiled.
chewing the crust
Fortunately for all you impatient pie lovers, manufacturers are now putting their pastry products in foil sleeves that heat up and create a crust in much the same way as a conventional oven. However, normal pastry is almost impossible to cook well in a microwave since water from inside the pastry makes it soggy and the temperature never gets high enough to produce a nice brown crust.
egg-plosion
Some foods are destined never to be cooked in a microwave. Whole raw eggs explode, as Percy Spencer found out whilst he was enjoying his microwaved popcorn.
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