Question

[ngô mai phương]

MICROWAVING
Microwaving is a method of cooking where food is bombarded by microwaves, usually
within an appliance called a microwave oven which excite the water, fat and sugar
molecules, thereby heating (cooking) both the outside and center of the food at the same
time. (1)…………………
(A common myth is that a microwave oven cooks from the center of the food outward. This
appears to happen because heat generated at the surface escapes more readily from the
surface of the food into the surrounding air.) One advantage of microwaving is that small
amounts of food can be heated very quickly, making it useful for reheating leftovers.
The disadvantage is that food which is microwaved does not undergo some of the chemical
reactions, such as browning, which makes the food visually attractive. Primitive microwave
ovens often do not cook evenly, leading to a concern that bacteria easily killed by more
traditional cooking methods may survive the quick cooking time in "cold spots", though the
food item as a whole is cooked to a safe average temperature. (2) ……
Some high-end microwave ovens are combined with a convection oven which basically
cook the food using microwave and hot air simultaneously to achieve both the fast cooking
time and browning effect.
(3) …………………
However microwave ovens are used in some fast food chains and special microwave bags
are available for cooking fowl or large joints of meat.
Professional chefs generally recommend using microwaves for a limited set of tasks,
including: melting fats (such as butter) and chocolate, cooking grains like oatmeal and grits,
cooking rice, thawing frozen meats and vegetables before cooking by other methods and
quickly reheating already-cooked foods.
Using a microwave to boil water is potentially dangerous, due to superheating. In a
microwave, water can be raised quickly to a temperature above the boiling point before
major bubbles form, especially if it is purified and in a very clean glass vessel. (4)
…………………
This effect is rare, even for scientists who try to deliberately recreate it, and any seed
whatsoever for boiling is likely to prevent the problem. Boiling water with, for instance, a
teabag already in it will prevent any dangers by providing a seed, as will using a mug that is
not perfectly clean.

The risk greatly increases when water has already been boiled once in the same container.
This situation can occur if the user of the oven boiled the water once, forgot about it, then
came back later to boil it again. The first time the water boils, the seed bubbles
(microscopic bubbles of air around which larger steam bubbles grow) are used up and
largely eliminated from the water as it cools down. When the water is heated again, the lack
of seed bubbles causes superheating, and a risk of a steam explosion when the water's
surface is disturbed.
Placing something in the water before heating can mostly alleviate this risk. If you are
planning to mix something with the water, say tea or hot chocolate, adding it before heating
will insure that the water boils. Otherwise, placing a wood object, for instance a chopstick,
in the water before heating will also work.
Care should be taken when removing heated water from a microwave. Make sure that the
hands are protected from possible liquid boil-over, place the container on a level, heat-
proof surface and stir liquid with a warm spoon. Also, never add powdered substances
(such as instant coffee or cocoa mix) to the container taken from the microwave, due to the
addition of all those seed bubbles and the potential for violent, spontaneous boiling. (5)
…………………
Metal objects, such as metal utensils, in a microwave oven can lead to dangerous situations.
Metals do not absorb microwaves effectively. Instead, metals reflect microwaves, thereby
preventing the latter from reaching the food. (6) …………………
Thin metal layers, such as metal foil and mugs with metal trim can melt or burn due to the
strong electrical currents that are generated in metal objects. However, small solid metal
objects, such as spoons, in combination with a large amount of absorbing food or liquid,
normally do not lead to problems.
This article is licensed under the GNU Free Documentation License. It uses material from the
Original Wikipedia article.