A good cook knows what ingredients to combine into a delicious meal. This short article in the “Ingredients” series focuses on the humble and ubiquitous onion. Virtually every cuisine uses the onion or onion variant as a basic flavoring. In fact, Julia Child once said, “It is hard to imagine a civilization without onions.”
Here we’ll take a look at what kinds of onions there are, their different tastes and qualities, and the different uses to which onions can be put. When you’re done reading you’ll feel a lot more confident going to the market and selecting onions, cooking with onions and creating recipes with onions as an ingredient.
What’s an Onion?
The Latin name for onion is “Allium cepa.” It’s related to other edible Allium species: leeks (Allium ampeloprasum or porrum); shallots (Allium ascalonicum); garlic (Allium sativum); and, chives (Allium schoenoprasum), among others. You may immediately recognize some common characteristics: they all have bulbs, are layered, and taste quite strongly. If you’re a gardener, you know that they grow tall and thin, that there is one flower to a stalk, and that they reproduce by budding off the bulb.
When you go to the market you may notice that there are several types of onion available. In North America the most common are the yellow onion, the white onion, and the red onion. You may also find small white pearl onions or Walla Walla sweet onions. Because onions are a foundation spice in many areas of the world, people have cultivated sub-species of the common garden onion, often named for where they come from. These different species have different flavors and uses and we’ll cover those below.
You can find an excellent resource on the history of onions in general and sweet onions in particular at Peggy Trowbridge’s About.com site, “Sweet Onion History.” The history of the onion is fascinating, but not the subject of this article. Here we’re more concerned with choosing, storing and cooking with onions.
How to Pick and Store an Onion
Onions should be firm and solid, heavy to the hand. There should be no soft or mushy parts. The “parchment” layer of thin skin should cover the whole onion, but not descend through more than one or two thin layers towards the heart. It’s said that the perfect onion has 13 rings, but of course you can’t count them in the grocery store.
Onions keep for a very long time if they are stored in cool, dark, dry places. If they are stored wet, however, they are prone to become moldy. Don’t buy onions that have mold on them (the mold can be dry and powdery, or, if the onion is very wet, it can be smeary like algae. If you find mold on an onion you store at home, quickly remove it from other onions and check them for mold. If it’s a small spot of mold you can cut it away, but if there is a large area of mold or if the onion is soft you should dispose of it in the compost heap or the garbage. When onions begin to sprout they are still edible, but they lose some of their flavor. When the sprouts grow large they suck moisture from the bulb and the onion changes texture and taste for the worse. The drier you keep them, the less likely they will sprout.
Onions labeled “Sweet” do not store as well as other onions, and are usually only available seasonally. They are mild and, as their name suggests, taste sweeter than more common onions. Use these soon after you buy them.
Onions come in sizes from small to large. I recommend that you consider how much onion you will actually use at a time. If you need small amounts of onion to flavor dishes, buy smaller onions. If you’re making sauce and need a lot of onion, go big. Just remember that cut and peeled onions are difficult to store properly. They can dry out, get mouldy and, if not kept in air-tight containers, make your whole refrigerator and/or kitchen smell like onion. An onion is considered “super-colossal” if it is 4.5″ in diameter or larger.
The best onions for eating raw are Sweet Onions. Varieties of Sweet Onion are usually only available April-August, depending on the region you live in.
Raw onions are primarily used as flavoring and to add crunchy texture to cold or hot foods. They can be chopped for salads, sliced for sandwiches, and pureed for dressings or sauces. They can also be eaten plain: Russians love to eat raw white onion with their black rye bread; a favorite combination is to take a shot of good vodka, bite into an onion, and follow it with a piece of the bread. (Repeat as necessary.) Onions can also be marinated and pickled in a variety of ways.
When using raw onions, it is particularly important to pay attention to the flavor and strength of the particular onion you are using. Peeling them under running water can help to cut the fumes, but the best method I’ve found for very sensitive people is to wear a pair of swimming goggles. Really; I’m not kidding.
How Strong is Your Onion?
Though you might buy the same brand of onion from the market again and again, one time the flavor will be strong and the fumes so powerful they burn your eyes, and another time they will be mild and almost fume-free. Onion strength within the same species vary depending upon the time of year they are grown, the conditions under which they are grown, their age at the time of harvesting, how long they have been stored, the quality of the soil, and the amount of water they receive. It’s important to remember this when you are cooking and to taste the particular onions you have chosen for your meal. “A cup of chopped onion” is simply a bulk measurement and doesn’t tell you anything about flavor. If your onions are very strong, use fewer. If they are weak and mild, you can use more. Except when you are baking, regard recipes as guidelines to use in your cooking: amounts and proportions are rarely absolute.
Different Kinds of Onions
Yellow Onions comprise about 70 percent of the onions available in supermarkets. They are easier to grow than red or white onions, have tougher skin and are not prone to showing the green streaks (from late harvest rains) or the sunburn that white onions can suffer. Yellow Onions can be strong or mild depending on the factors discussed above.
White onions grow very large and are more tender than Yellow Onions. Like yellow onions, they vary a great deal in strength, pungency and fume emission. They are very popular for Mexican and Latin American cooking as they tend to be tangier and more crisp tasting than Yellow Onions. They are very susceptible to mold, but store for a long time if kept very dry.
Red Onions grow to a smaller size than Yellow Onions. They are also often milder and sweeter, with a distinctive taste and texture. One variety of red onion is the Bermuda, which usually shows up in supermarkets in the spring.
Yellow Granax (sweet onions, called Vidalia when grown around Vidalia, Georgia and called Maui Onion when grown on that island in Hawaii). The Cippolini is an Italian sweet onion. Other varieties include Sweet Imperial, Carzalia Sweet, Oso, Arizona, and the strangely named Texas 1015Y. Remember these are hard to store.
Walla Walla Onion (called Walla Walla Sweets when grown around Walla Walla, Washington). This onion originated in Corsica and was brought to Washington by immigrants.
Pearl Onions (also called Boiling Onions) are small white onions under 2″ in diameter. They are difficult to peel, but they are a lovely addition to soups and stews, and they are a joy to pickle. They are rarely eaten raw.
Dried Onions and Preserved Fried Onions
Dried onions are never as good as fresh. Use dried minced onion as a substitute for fresh only when absolutely necessary. Personally, I stay away from onion powder entirely.
Preserved fried (crispy) onions are often used to garnish finished dishes and can be purchased in many Asian food markets.
Cooking with Onions
Onions should always be cooked at medium or lower heat because they change their taste and become bitter if cooked too hot. Onions can be cooked into six different forms:
If you cook an onion for a medium- to long-period of time over a low heat they will turn soft and transparent. The longer you cook them at this temperature, the softer and less visible they will become. Sauteing onions to transparency is the method often used for introducing them into sauces and stews. Many sauces begin with the instruction to “melt” your onions into some sort of oil, often combined with garlic and tomatoes. When you put raw onions into liquid (like soups and stews) and boil them, you also achieve the state of transparency. In the first case you suffuse the oil with the onion taste. In the second, the onion taste diffuses through the boiling or simmering liquid.
The taste of browning onions is indeed delectable and can be smelled throughout the house (and even sometimes out onto the street), especially when combined with garlic. Browned onions are sauted over a medium heat just to the point of achieving a golden brown color around the edges. If you overcook the onions and burn them, the smooth, mellow flavor will be replaced by a sharp, bitter, burnt taste, so it is very important to keep a close watch on onions if you are cooking them over a medium heat. Never cook them higher than medium. Browned onions are also used as the basis for sauces or stews, but they impart a very different flavor than transparent onions. The best description I can give is that they have a “toasted” flavor. The flavor suffuses the oil medium in which they are browned and thus anything cooked in that oil will also taste of browned onions.
If you dip onions in a batter and then drop them hot oil they will fry quickly. Properly fried onions have a crispy batter and reach a soft transparent or semi-transparent state. They must never burn on the outside. You can fry cut up onions (as in Onion Rings) or the whole onion (a popular dish in many steak houses). Fried onions are usually served as garnishes or side dishes.
4) Baked or roasted:
Onions can be put in an oven and baked, either on their own with some sort of sauce (balsamic vinegar and garlic, for example), or as a part of a roasted dish (pot roast, tandoori, roast beef, etc.). Roasted onions may toast lightly on the outside and be soft in the middle, or they may become completely soft and transparent. The end state depends on the amount of moisture in which the dish is cooked.
Onions grill very well, but since they burn quickly at high temperatures it’s best to add them late to the barbecue grill or skewer. Watch grilled onions carefully to ensure that they brown but do not burn. Grilled onions usually do not cook long enough to be soft in the middle, so they are often toasted and soft on the outer layers, and retain some crunch and bite on the inside. This makes them a particularly lively and tasty accompaniment to strongly flavored dishes like shishkebob.
6) Pickled or marinated:
The most commonly pickled onions are boilers, but large onions can also be pickled if they are cut up. The best pickled onions retain freshness and crunch while merging their flavors with strong pickling spices. Most pickled onions are lightly boiled (less than three minutes) before being put in the preserving liquid. This liquid combines vinegar with other pickling spices. If you arepickling for storage make sure to follow safe canning rules. Unlike most of the recipes I discuss, pickling is a delicate procedure and proportions of preserving liquid need to be measure carefully. For a great guide see Clemson Universities “Pickle Basics.”
Marinated onion dishes should be used within a week. Often the same spices are used for marination as for pickling, but the proportions and procedure are not so important since the pickled will not be canned and stored.
Most good cooks have onions on hand since they use them in many dishes and storage onions (non-sweet) keep for long periods of time. Learn to distinguish varieties of onion by tasting them and using them in your cooking experiments. A properly-used onion can ring flavor and taste out of scant ingredients. If you don’t feel like cooking, you can simply contemplate the onion. It inspires deep thoughts, or at least it did in Carl Sandburg, the famous American poet. Sandburg wrote: “Life is like an onion: you peel it off one layer at a time, and sometimes you weep.”
In addition to being a scholar, Shawn Scott, Ph.D., is a culinary enthusiast and has worked as a professional caterer and chef. Now retired from teaching, Scott has decided to share the collected wit and wisdom of almost forty years of cooking and food lore. You can read more about Scott’s ideas on innovation and improvisation in the kitchen at “Recipe-Free Cooking” — the continually updated blog on creative cooking made easy.