native to: Asia
in season here: summer-fall, but they store well and can be found in farmers' markets nearly all year
There are two general categories of onion, the mature onion and the scallion, green onion, or salad onion. The shallot, while related to onions, is a different vegetable. Scallions are baby onions, so their season is earlier and shorter than mature bulbs. When the crop first comes on, you'll find fresh onions, which are also sometimes described as salad onions (just to be confusing) and need to be eaten fairly soon. Onions for storage must be "cured" by drying. This can be accomplished by pulling the plants and then leaving them out in the field for a few days (assuming the weather is dry). Then they can be gathered up and hung in bunches or otherwise stored in dry conditions until ready for use. Onions cured this way keep best in a cool dry place such as a root cellar; if you have to keep them in a refrigerator, make sure they've got a nice dry spot.
Some believe that once an onion is cut, it will attract germs, making it useful to leave on the counter to purify the air but unhealthy to eat after a day. Since I almost never use a whole onion, I avoid the whole issue by cutting up the whole onion and freezing what I don't use. Onions frozen like this are fine to use for cooking, although the texture will suffer a little. Eating raw onions is also a folk remedy for colds.
As early as the sixth century B.C., an Indian medical treatise, the Charaka Sanhita, recommended the onion as a diuretic, and said it was good for digestion, the heart, the eyes, and the joints. Ancient Greek athletes ate onions and drank onion juice to fortify themselves for the Olympic Games. According to Pliny the Elder, the ancient Romans used onions to cure poor vision, induce sleep, and heal mouth sores, dog bites, toothaches, dysentery and lumbago.
So, what do you get from eating onions, besides onion breath? They're excellent sources of vitamin C, sulphuric compounds, flavonoids, and phytonutrients, so they help prevent Parkinson's disease, cardiovascular disease, cancer, high blood pressure, and stroke. They also help reduce inflammation. One of onions' flavonoids is quercetin, which some animal studies suggest helps prevent plaque buildup in the arteries as well as its general value as an antioxidant. It also reduces allergic reactions by stopping your body from producing histamines. One study even found that it relaxes the airway muscles and might be able to relieve asthma symptoms. Red onions are especially high in quercetin.
Their anti-inflammatory qualities come from sulphur compounds, which are also what makes you cry when cutting them. For the best dose of sulphur, eat your onions raw. There is a high concentration of flavonoids in the outer layers of an onion, so you'll get the most flavor and anti-cancer action if you don't peel off any more layers than necessary.
Read more:
label-style nutrition data for cooked onions
label-style nutrition data for raw onions
lots of interesting onion facts
Versión en español: this post is also available in Spanish
Esperanta traduko: this post is also available in Esperanto, because Dana is a language geek.
