This came from research that Chris did over at The Cooking Dish blog.
If you’ve ever been in the grocery store buying onions and couldn’t figure out which color of onion to buy, you’re not alone. Or perhaps you’re cooking and realize your recipe calls for a white onion and all you have are yellow onions… dont’ worry. There are many onions out there, each with their different purposes, but typically they fit into two categories, green and dry onions. This post discusses the dry onions (red onions, yellow onions, and white onions). Although there are many types of each of these dry onions, the general rules for them are as follows.
Yellow onions are the most popular cooking onions because they add excellent flavor to most stews, soups, and meat dishes. In fact, typically when a cooked recipe calls for onion, yellow onion is a safe way to go. Yellow onions have a yellow-brown papery skin on the outside and a white flesh.
I always know when someone is cooking with yellow onion because my eyes start to water (an effect of higher sulfur content). Because the yellow onion has such high sulfur content, it has a more pungent flavor and smell, which typically makes it too strong to eat raw unless there are other ingredients to counter-balance the flavor. In my own cooking, I use yellow onions in stews, soups, sautéed dishes, and shish kabobs. They have excellent flavor when cooked, and I rarely cook without them.
White onions have an all-white skin (I’ve seen them with an off-white tint before) and an all-white flesh. They have a slightly milder flavor than the yellow onion and are a great substitute if you’re in need of an onion flavor, but don’t want it to be too powerful. White onions are commonly used in Mexican cuisines.
You’re most likely to see red onions in non-cooked dishes, such as salads and sandwiches. Of the different colored onions, the red onion is the most mild, sweet onion. Red onions have the purplish-red skin which color is layered though it’s white flesh. I personally don’t like to cook heated dishes with red onion because it doesn’t produce enough onion flavor to enhance my meal. (Cooking an onion diminishes its flavor, but increases the flavor of the food around it).
How to Pick a Good Onion
In general, when you’re choosing onions in the store, the best ones will be firm, have a crackly outer skin, and have a mild scent. If their scent is overwhelming it’s a good sign the onion is starting to spoil. Avoid onions with dark spots or mold as well, though every once in a while I’ll still purchase those if I’m going to use them right away (I guess that’s my altruistic side coming out–take one for the team, you know). On another note, onions tend to store better in a slightly cooler, darker area, although the fridge is not recommended. The onion smell has a tendency to spoil the flavor of other foods in the fridge.
Onion Nutrition Data
More detailed nutrion information can be found at: NutritionData.com.