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Microwaves and How They Work
Microwaves are a form of high frequency electromagnetic
waves (app. 12 cm wave length) similar to those used by a
radio.
Electricity is converted into microwave energy by the
magnetron tube. The microwaves travel from the magnetron
tube to the oven cavity where they are reflected, transmitted
or absorbed.
Reflection
Microwaves are reflected by metal
just as a ball is bounced off a wall.
A combination of stationary (interior
walls) and rotating metal (turntable
or stirrer fan) helps assure that the
microwaves are well distributed
within the oven cavity produce even
cooking.
Utensil Guide
Aluminum foil
Glass tray
Browning dish
Dinnerware:
Oven/Microwave safe
Non-Oven/Microwave safe
Disposable polyester/Paperboard dishes
Glassware:
Oven glassware & ceramic
Non-heat resistant
Metal cookware
Metal twist-ties
Paper towels and napkins
Plastic dishes: Microwave safe
Non Microwave safe
Microwave safe plastic wrap
Straw, Wicker, Wood
Thermometers: Microwave safe
Conventional
Grease proof paper
Transmission
Microwaves pass through some
materials such as paper, glass and
plastic much like sunlight shining
through a window. Because these
substances do not absorb or reflect
the microwave energy, they are
ideal materials for microwave oven
cooking containers.
Absorption
Microwaves are absorbed by food.
They penetrate to a depth of about
2-4 cm. Microwave energy excites
the molecules in the food (especially
water, fat and sugar molecules), and
causes them to vibrate very quickly.
The vibration causes friction and
heat is produced. In large foods, the
heat which is produced by friction is conducted to the center
to finish cooking the food.
Food Characteristics
FOOD CHARACTERISTICS
Microwave
Food characteristics which affect conventional cooking are
No
more pronounced with microwave heating.
Yes
Size –– Small portions cook faster than large ones.
Yes
Shape –– Uniform sizes
heat more evenly. To
Yes
compensate for
No
irregular shapes, place
Yes
thin pieces toward the
centre of the dish and
Yes
thicker pieces toward
No
the edge of dish.
No
Starting Temperatures –– Room temperature foods take
No
less time to heat up than refrigerator frozen foods.
Yes
Bone and Fat –– Both
affect heating. Bones
Yes
may cause irregular
No
heating. Large amounts
Yes
of fat absorb microwave
energy and meat next
Yes
to these areas may
Yes
overcook.
No
Yes
Density –– Porous, airy foods take less time to heat than
heavy, compact foods.
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