Radiation

1
Radiation

• And the Microwave Oven

2
Radiation

• Involves the transfer of heat in the form of
  waves through space.
• The microwave oven uses radiation to cook food.
• Broiling, grilling and rotisserie cooking use
  radiant heat.
• Is responsible for most browning of foods.

3
The Microwave Oven

• Has an electron tube called a magnetron tube
  which converts electrical energy into microwaves.
• Microwaves are actually low frequency waves of
  radiant energy.

4
Microwaves are about the diameter of a pencil and
are about 1 ½ inches long.

• Microwaves
• Cannot pass through metal.
• Can penetrate paper, glass and plastics.
• Can only travel in a straight line.

5
When microwaves penetrate a piece of food, it
causes the particles to become agitated and move
around.

• The movement causes friction, which produces
  heat. The heat cooks the food.

6
Foods that are high in water, fat and sugar are
more easily agitated and therefore cook faster
than other foods in the microwave oven.

• Foods with a high water content cook the fastest
  of all. Many foods have a high water content.

7
Microwave ovens have hot spots

• Since the magnetron tube is located on one side
  of the oven, the microwaves bounce around in an
  uneven pattern. Certain areas in the oven will
  get hit more frequently.
• Dishes need to be turned halfway through cooking
  time, food should be stirred when possible or a
  turntable should be used if one is available to
  promote even cooking.

8
Microwave Tips

• Do not worry the size of a microwave is larger
  than the tiny holes in the metal screen behind
  the glass in the door,so the waves cannot escape.
• Microwaves bounce off metal. Do not try to cook
  in a metal pan or on foil. The microwaves will
  not be able to penetrate the food and it will not
  cook!
• The heat from food will transfer to the dish,so
  always use pot holders.

9
Steam can build up in tightly sealed foods or
containers and cause them to explode.Always
pierce vegetables or fruits with thick skins as
well as egg yolks.

• Never try to cook eggs in their shells.
• Vent plastic coverings on dishes.
• Use a turntable or rotate the dish halfway
  through the cooking time so that the food will
  cook evenly.
• Food will continue to cook for several minutes
  after the microwave stops, so allow for
  approximately five minutes of rest time.