Onions are the third most commonly consumed fresh vegetables in the US, after potatoes and tomatoes. (Fourth if you combine head and leaf lettuces.) Per capita onion consumption has risen more than 70% in the last two decades, from 12.2 pounds in 1982 to 20 pounds in 2010.
Sweet onions, such as Vidalia, Maui and Walla Walla, are in season only in late spring and summer months, but storage onions-as their name indicates-can be enjoyed all year. These include yellow onions (the most commonly grown in the US), white, red and Spanish varieties; red onions are highest in flavonoid content, followed by yellow and then white. Green onions, also called scallions, are immature onions harvested early. Most pearl onions are also ordinary onions grown to a small size, although there is a true pearl onion related to leeks. Shallots also belong to the same species (Allium cepa) as onions.
When selecting dry bulb onions, look for those that are firm and have little or no smell. Avoid any with cuts, bruises or blemishes. Onions were among the Environmental Working Groups 2014 Clean 15 for which buying organic to minimize pesticide contamination is optional if youre on a budget <www.ewg.org>.
Store unpeeled onions in a cool, dry, dark place. Storage at cool temperatures also seems to better preserve their antioxidants. Allow for air circulation around the onions and do not store in plastic bags. Peeled or cut onions should be refrigerated in sealed containers for up to a week.
Peel your onions carefully, as the flavonoids tend to be concentrated in the outer layers; dont overpeel and lose these healthy compounds along with the papery outer layer.
Blame a gas, propanthial S-oxide, produced when onions are cut, for their tear-producing properties. To reduce the eye-watering effects, cut onions as far from your face as possible, so the gas can dissipate. Some sources suggest refrigerating onions for 30-60 minutes before slicing. You can also cut them under running water, but some of the nutrients and flavor will be washed away as well.