Onion Nutrition, Selection, Storage and Availability Onions are low in calories and fat. Onions provide some fiber, potassium and Vitamins C and B6, while scallions and green onions contain Vitamin A. Research also suggests that oils in onions may help prevent heart disease by lowering LDL cholesterol in the blood stream and increasing levels of HDL cholesterol. Onions can be broken down into two different categories: 1.) storage onions; red and yellow globe, Spanish, white, cipolline and 2.) pearl or spring/summer onions (scallions). Scallions are sweeter and are more perishable than storage onions. When selecting storage onions, make sure they are firm and dry and have no soft spots. Also, the neck of storage onions should be closed and dry. The best scallions have crisp green tops with slender bottoms. Storage onions can be kept for several months when stored in a cool dry place. After being cut, onions must be refrigerated in a tightly sealed container to prevent their strong odor from affecting other foods. Scallions/green onions should be stored in the refrigerator in a plastic bag or moist paper towel. Fresh onions are available in Wisconsin in late summer and fall while scallions are available in spring and early summer.
Onion Extras The pungency of onions varies from very sweet and mild to very strong. The same onions grown in different locations can have very different levels of taste. Freshly harvested onions are much stronger than stored onions, which mellow over time. When chopping large amounts of strong onions, try refrigerating them before cutting, or cutting onions under water to avoid watery eyes.
Information from the Wisconsin Fresh Market Vegetable Growers Association, the Wisconsin Department of Agriculture, Trade & Consumer Protection and the University of Wisconsin-Extension.