What would a recipe be like if we did not have onions? The distinctively pungent smell and taste of onions rounds out the flavours of almost any type of cuisine. For centuries, onions have added value to our cuisine and have also been thought of as having therapeutic properties.
The word onion comes from the Latin word unio for “single” or “one” because the onion produces a single bulb. The name also suggests the union of the many separate concentrically arranged layers of the onion. Onions are native to Asia and the Middle East and have thought to be cultivated for over five thousand years-they were highly regarded by the ancient Egyptians. Often the ancient Egyptians used them as currency to pay the workers who built the pyramids, and also placed them in the tombs of kings (Tutankhamen) so that the kings could carry them as gifts in the afterlife. In India in the 6th century onions were used as a medicine. The ancient Greeks and Romans often dressed up onions with extra seasonings in their cooking because they did not find them spicy enough. Many European countries during the Middle Ages served onions as a classic healthy breakfast food. It should be noted that Christopher Columbus brought onions with him to the West Indies and spread their cultivation from there throughout the Western Hemisphere. Today the leading producers of onions are China, the United States, Russia and Spain, among others.
Onions are available in fresh, frozen, canned and dehydrated forms. They can be used in almost any type of food, cooked, in fresh salads or as a garnish, and are usually chopped or sliced. Onions are mainly used as an accompaniment to a main course and are rarely eaten on their own. There are many different types of onions ranging from sharp and pungent to mild and sweet.
Depending on the variety, onions range in size, colour and taste. There are generally two types of large, globe-shaped onions, classified as spring/summer or storage onions. The spring/summer class includes onions that are grown in warm weather climates and have characteristic mild or sweet tastes. This group includes the Maui Sweet Onion (in season April through June), Vidalia (in season May through June) and Walla Walla (in season July and August). Storage onions are grown in colder weather climates and, after harvesting, can be dried out for a period of several months. They generally have a more pungent flavour and are named by their color: white, yellow or red. Spanish onions are classified as storage onions. There are also smaller varieties of onions, such as the green onion (also called scallions) and the pearl onion.
Onions are members of the Allium family and are rich in powerful sulphur-containing compounds which are responsible for their pungent odours and for their many health-promoting effects. When an onion is sliced the cells are broken, which allows enzymes called alliinases to break down sulphides and generate sulphenic acids (amino acid sulfoxides). The Sulphenic acids are unstable and decompose to produce a gas called syn-propanethial-S-oxide. Then this gas reaches the eye it reacts with the water in the eye to form a diluted solution of sulphuric acid which irritated the nerve endings in the eye. Your eye then produces tears to dilute and flush out the irritating substance. This is what makes your eyes sting and water when slicing onions.
Eye irritation can be reduced by supplying an ample amount of water to the reaction, which prevents the gas from reaching your eye. This is why it is thought to be helpful to cut onions under running water or submerged in a bowl of water. Rinsing the onion and leaving it wet while slicing may also be helpful. Other tips to help reduce eye irritation are by freezing onions, which prevents the enzymes from activating, limiting the amount of gas generated. Also, using a very sharp knife while chopping will limit the cell damage thereby reducing the amount of enzymes released. Lemon will help to remove the characteristic odour of the onion.
As mentioned, onions are thought to produce many health benefits. Onions are a good source of chromium, the mineral component in glucose tolerance factor, a molecule that helps cells respond to insulin. Diabetic clinical studies have shown that the chromium produced by onions can decrease fasting blood glucose levels, improve glucose tolerance, lower insulin levels and decrease total cholesterol and triglyceride levels, as well as increase good HDL-cholesterol levels.
One cup of raw onion contains over 20% of the daily value for chromium. Since chromium levels are depleted by the consumption of refined sugars, white flour products and the lack of exercise, marginal chromium deficiency is common in the United States.
A case-control study from Southern European populations suggests that making onions and garlic a staple in your diet may greatly lower your risk of several common cancers. Eating onions two or more times per week is associated with a significantly reduced risk of developing colon cancer. As well, the regular consumption of onions has been shown to lower high cholesterol levels and high blood pressure, both of which help prevent atherosclerosis and diabetic heart disease, and reduce the risk of heart attack or stroke.
Onions may also help maintain healthy bones. A newly identified compound in onions, gamma-L-glutamyl-trans-S-1-propenyl-cysteine sulphoxide (GPCS) inhibits the activity of osteoclasts (the cells that break down bones). This may be especially beneficial for women who are at increased risk for osteoporosis as they go through menopause.
Other potential health benefits of onions include several anti-inflammatory agents that reduce the severity of symptoms associated with the pain and swelling of osteo- and rheumatoid arthritis, the allergic inflammatory response of asthma, and the respiratory congestion associated with the common cold. Also, quercitin and other flavonoids found in onions work with vitamin C to help kill harmful bacteria and are helpful when added to soups and stews during cold and flu season.
In many parts of the undeveloped world, onions are also helpful in healing blisters and boils. Onion extract (Mederma) is used in the United States in the treatment of topical scars.
When choosing onions, choose onions that are clean, have no opening at the neck and have crisp, dry outer skins. Avoid onions that have sprouted, have signs of mold, or once that have soft spots, moisture at the neck, and dark patches which may indicate signs of decay. When choosing scallions, choose those that have green, fresh-looking tops which are crisp and tender. They should be white in colour for 2-3″ along the base. Avoid scallions that look wilted or have yellowed tops.
Store onions are room temperature, away from bright light and in a well-ventilated area. Hanging them in a wire basket or perforated bowl for ventilation is ideal. Onions that are more pungent in flavour, such as yellow onions, can be stored for longer periods that the sweeter variety of onions, such as white onions. Scallions should be stored in a plastic bag in the refrigerator and will keep well for about a week. Store all onions away from potatoes as the onions will absorb the moisture from the potatoes and cause them to spoil more easily. Cut onions should be wrapped tightly in plastic wrap or sealed in a container, and should be used within a couple of days since they tend to oxidize and lose their nutrient value quickly. To maintain the best taste of cooked onions, they should be stored in an airtight container and used within a few days. Never place cooked onions in a metal container since this will cause discoloration. Peeled and chopped onions may be frozen raw, but this can cause them to lose some of their flavour.
Onions can be eaten raw or cooked in almost any way imaginable-broiled, boiled, baked, creamed, fried, deep-fried, or pickled. They are great in soups, stews and combined with meats and vegetables. They add a versatility to your dishes that is hard to beat.