Do
microwaves really cook
food from the inside out?
The
ability of microwaves to cook food was accidentally discovered by Percy
LeBaron
Spencer of the Raytheon Company in the 1940s when he found that they
melted
a candy bar he had in his pocket. In 1947, the first commercial microwave
oven hit the market (Raytheon "Radarange"). These primitive units where
gigantic
(shown above) and enormously expensive, standing 5 1/2 feet tall,
weighing
over 750 pounds, and costing about $5000 each. Microwaves
are a form of electromagnetic radiation that have shorter wavelengths
than
television signals but longer wavelengths than visible light. One curious
property of microwaves is their ability to excite or agitate water molecules
but not other molecules. The reason for this is that water molecules have a
positive end (hydrogen) and a negative end (oxygen). Most other types of
molecules
are neutral.
Microwaves act like little magnets, attracting and repelling the positive and
negative ends alternately, thus causing water molecules to spin. Microwave
radiation alternates its field 2,400,000,000 times per second, spinning the
water molecules incredibly fast. All this spinning of molecules creates a
great deal of friction,
and friction causes heat. Most
foods are made up of molecules of carbohydrate, fat, and protein. Interspersed
among the food molecules are water molecules. The spinning water molecules heat
up the surrounding molecules and cook the food. Conventional ovens heat up the
air
that surrounds the outer layers of food. The heated outer layers gradually
transfer
the heat to the inner layers of food, cooking it from the outside
in. In
microwave cooking all the food molecules are heated approximately at the same
time. However, since the air inside the microwave oven remains cool, the outer
layers of food during cooking may be cooler than the inner layers, due to heat
loss
to the air. This gives the impression that the inside has cooked first.
One common complaint about microwave cooking is that bread products come out
soggy, not crisp. This is because in microwaves, the heated water molecules rise
quickly to the surface of the food, condensing into water droplets on the surface.
This
results in soggy bread. In conventional ovens, the heated water vapor
rises more slowly
and then evaporates rather than condensing when it hits
the hot, dry oven air. As a
result, bread will be crisp on the outside and
moist on the inside, where some
water remains, unless the bread is overcooked. From
... "The Thoughts for the Throne" by Don Voorhees
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