The
archaeological and literary evidence
suggests cultivation probably took place
around two thousand years later in ancient
Egypt. This happened alongside the
cultivation of leeks and garlic and it is
thought that workers who built the pyramids
were fed radishes and onions.
The onion is easily grown, transportable,
and has good storage qualities. Egyptians
worshipped it, believing that its spherical
shape and concentric rings symbolized
eternal life. Onions were even used in
Egyptian burials as evidenced by onion
traces being found in the eye sockets of
King Ramses IV. They believed that if buried
with the dead, the strong scent of onions
would bring breath back to the dead. The
onion then made its way to Greece where
athletes ate large quantities of onion
because it would lighten the balance of
blood. Roman gladiators were also rubbed
down with onion to firm up their muscles. In
the Middle Ages onions were such an
important food that people would pay for
their rent with onions and even give onions
as gifts. Doctors were also known to
prescribe onions to end headaches,
snakebites and hair loss. The onion was
introduced to North America by Christopher
Columbus on his 1493 expedition to Haiti.
Onions are one of the earliest crops
mentioned in written text, in the Bible's
Book of Numbers (11:5) as part of the
Egyptian diet of that time. Six types of
onions were known at the time of Pliny the
Elder's Natural History.
Culinary and medicinal uses
Onions are
available in fresh, frozen, canned, and
dehydrated forms. Onions can be used,
usually chopped or sliced, in almost every
type of food, including cooked foods and
fresh salads, and as a spicy garnish; they
are rarely eaten on their own but usually
act as accompaniment to the main course.
-
Depending on the variety, an onion can be
sharp and pungent or mild and even sweet.
- Chopped,
it is one of the three vegetables
considered the holy trinity of Louisiana
Creole and Cajun cuisine.
- Cocktail
onions, or pickled pearl onions, are used
to garnish drinks such as Gibsons.
They appear
to be at least somewhat effective against
colds, heart disease, diabetes, and other
diseases and contain anti-inflammatory,
anticholesterol, anticancer, and antioxidant
components such as quercetin.
In many parts of the underdeveloped world,
onions are used to heal blisters and boils.
In the United States, products that contain
onion extract (such as "Mederma") are used
in the treatment of topical scars.
Why do
onions make you cry?
As onions are sliced, cells are broken open.
Onion cells have two sections, one with
enzymes called alliinases, the other with
sulfides (amino acid sulfoxides). The
enzymes break down the sulfides and generate
sulfenic acids. Sulfenic acid is unstable
and decomposes into a volatile gas called
syn-propanethial-S-oxide. The gas then
dissipates through the air and eventually
reaches one's eye, where it will react with
the water to form a mild solution of
sulfuric acid. The sulfuric acid irritates
the nerve endings in the eyes, making them
sting. The tear glands then produce tears in
response to this irritation, to dilute and
flush out the irritant.
The release of gas can thus best be
prevented by cutting the onions under
running tap water or completely under water,
though this may not be very practical.
Wetting the onions and your hands before
slicing will lessen the effect, as some of
the gas will react with the moisture on the
onions and on your skin (instead of the
moisture on your eyes). This reaction may
result as an odor which may be removed with
lemon. It also helps to breathe exclusively
through the mouth during the preparation.
Using a sharp knife will rupture fewer cells
and cause less eye irritation. For more tips
and information, please check links in
External links section. Chilled onions
(onions kept in the fridge for a while) will
make you 'cry' less than onions kept at room
temperature because lower temperature
inhibits the enzymes and gas diffusion.
Also, some people 'freeze' the knife (leave
it in the freezer for around 2 minutes)
before cutting the onions to prevent the
tears.
Different species of onions will release
different amounts of sulfenic acids, thus
some will cause more tear formation and
irritation than others.
Types of
onion (Allium cepa)
- Bulb
onions - Grown from seed (or onion sets),
bulb onions range from the pungent
varieties used for dried soups and onion
powder to the mild and hearty Sweet
onions, such as the Vidalia from Georgia
or Walla Walla from Washington that can be
sliced and eaten on a sandwich instead of
meat.
-
Multiplier onions - Raised from bulbs
which produce multiple shoots, each of
which forms a bulb.
o Shallot (most of the types in the
markets are Allium cepa)
o Potato onion
- Tree
onions or Egyptian onions - These produce
bulblets in the flower head, and are the
result of hybridization between Allium
cepa and welsh onions.
Related
species
The genus Allium is a large one, and most of
the species are considered to be "onions" in
the looser sense. Commonly raised vegetable
alliums include the leeks, garlic, elephant
garlic, chives, shallots, Welsh onions and
garlic chives. There are also species, such
as Allium moly, grown for ornament.
Several species of Allium, including A.
canadense and A. diabolense, can be
collected in the wild and their leaves and
bulbs used as food. |
Onion in the
general sense can be used for any plant in
the Genus Allium but used without qualifiers
usually means Allium cepa L., also called
the garden onion. Onions (usually but not
exclusively the bulbs) are edible with a
distinctive strong flavor and pungent odor
which is mellowed and sweetened by cooking.
They generally have a papery outer skin over
a fleshy, layered inner core. Used worldwide
for culinary purposes, they come in a wide
variety of forms and colors.
