MICROWAVE TESTS

13 Sep 2004, 05:05:48 PM

Reporter: Adene Cassidy

It was an easy accident, so easy this story should serve as a warning to any Australian who thinks their microwave oven is safe.

Like most 5 year olds these days Danielle Sharp can operate a microwave, with supervision from Mum Roslyn, it was a household item she felt comfortable enough to use every day.

On this day, Danielle didn't do anything differently, she waited while her pasta cooked, opened the door when it beeped, the difference, the water had gone way beyond boiling point, so hot the steam and heat from the container overwhelmed the little girl and she lost her grip, the water causing horrific burns from her wrist to her shoulder.

It's called superheating, a microwave oven can not only boil water it can superheat it, taking it over and above the boiling temperature of 100 degrees.

We asked Professor Joe Wolfe, from the physics department at the University of New South Wales to demonstrate just how easy it is to superheat water in a microwave.

Superheating happens when the water gets hot and the container stays cold, there's no steam and the water reaches 101 or 102 degree Celsius, beyond it's natural boiling point. The extra energy makes steam in a hurry, adding coffee or soup mix for example causes it to explode, often violently.

Dr John Harvey runs the burns unit at the Childrens' Hospital at Westmead, alarmingly he says household scalds are on the rise.

In the early 1990's 62% of Australian households owned a microwave, now it's more than 85%. Originally radiation emissions were a big concern but now with improved designs that's hardly a problem, but improved designs have also increased the power.

Janelle bloom is one of Australia's leading experts on microwave ovens and cooking, she has this advice for microwave users:

Apply the same principal when you're considering whether or not food should be covered, if you need to cover it on a stove, then cover it in the microwave, obviously with a microwave safe lid or container.

Never re-heat using takeaway containers or Styrofoam cups, and to avoid superheating don't use shiny new containers or glassware ... your old cracked mug or crockery, believe it or not, is safer. If you're concerned about superheating stir the water with a wooden spoon before taking it out.

Another misconception about microwave cooking is that it takes all the goodness out of food. But we put this theory to the test on legs of lamb and our results showed in a microwave the protein level increased 14% from raw, but not as much as in the oven, 22% increase, and 21% for the frying pan.

In the meantime the Sharp family continue to use their microwave, but have warn parents and children to take care.