The onion (Allium cepa), also known as the bulb onion, common
onion and garden onion, is the most widely cultivated species of
the genus Allium.
Onions pickled in vinegar are eaten as a snack. These are often served as
a side serving in fish and chip shops.
Common onions are normally available in three colors: yellow, red, and
white. Yellow onions are full-flavored and are a reliable standby for
cooking almost anything. Yellow onions turn a rich, dark brown when cooked
and give French onion soup its tangy sweet flavor. The red onion is a good
choice for fresh uses or in grilling and char-broiling. White onions are
the traditional onion used in classic Mexican cuisine. They have a golden
color and sweet flavor when sautéed.
While the large mature onion bulb is the onion most often eaten, onions
can be eaten at immature stages. Young plants may be harvested before
bulbing occurs and used whole as scallions. When an onion is harvested
after bulbing has begun but the onion is not yet mature, the plants are
sometimes referred to as summer onions.
Additionally, onions may be bred and grown to mature at smaller sizes.
Depending on the mature size and the purpose for which the onion is used,
these may be referred to as pearl, boiler, or pickler onions. Onion seed
may be "sprouted", and the resulting sprouts used in salads, sandwiches,
and other dishes. Onions are available in fresh, frozen, canned,
caramelized, pickled, powdered, chopped, and dehydrated forms.
Onion powder is a spice used for seasoning in cooking. It is made from
finely ground, dehydrated onions, mainly the pungent varieties of bulb
onions, which causes the powder to have a very strong odor. Onion powder
comes in a few varieties: white, yellow, red and toasted.
Possible medicinal properties and health effects
Wide-ranging claims have been made for the effectiveness of onions against
conditions ranging from the common cold to heart disease, Diabetes,
osteoporosis, and other diseases. They contain chemical compounds believed
to have anti-inflammatory, anti-cholesterol, anticancer, and antioxidant
properties. Preliminary studies have shown increased consumption of onions
reduces the risk of head and neck cancers.
In many parts of the undeveloped world, onions are used to heal blisters
and boils. An application of raw onion is also said to be helpful in
reducing swelling from bee stings. Onions may be beneficial for women, who
are at increased risk for osteoporosis as they go through menopause, by
destroying osteoclasts so they do not break down bone.
Onions have the potential to alleviate or prevent sore throat. Onion in
combination with jaggery has been widely used as a traditional household
remedy for sore throat in India.
For all varieties of onions, the more phenols and flavonoids they contain,
the more reputed antioxidant and anticancer activity they provide.