Cooksbakesbooks asks via twitter:
“I use oniony vegs basic’ly interchangbly, whtvr’s on hand. How do shallots scallions onions leeks etc. compare chem/physically?“
Oh, alliums: you are so tasty. And there are a lot of you. Upwards of 750 types. So many, in fact, that I’m not going to try to catalog you all. Still, we can do a quick tour. Alliums are perrinnels, meaning that if you plant them once and maintain them, they’ll bloom year after year. If you plant them once and eat them, they will probably have a difficult time blooming, however, so you might have to re-plant them.
Alliums are generally bulbous, like tulips. Most of the time, we eat the bulb, especially in the case of onions, shallots, and garlic. Occasionally we eat the leaves, in the case of garlic, chives, and leeks. The bulbs are the batteries of the plant world. Throughout the year, the onions and their ilk will grow some leaves, soak up nutrients, absorb sunlight, and store it all in the bulb, which is hidden safely underground. When winter comes, and the weather turns unfriendly, the allium can remain safely underground until the weather turns nice, then use all of that energy to sprout again. Hence the perrennial nature.
Unlike fruits, alliums do not want to be eaten. Eat a fruit, and you’re probably going to spread its seeds one way or another, so most fruits have seeds that are meant to be consumed. Alliums, because they store all of their energy for re-growth in the tasty part of the plant, most emphatically do not want to be eaten.
In order to prevent discourage your allium enjoyment, the plants will absorb sulfur from the ground and store it in its cellular fluids. Floating in that fluid is a vacuole filled with enzymes. If you puncture the vacuole, perhaps by cutting an onion with a knife or by biting into it, then the vacuole will release the enzymes turning the sulfur into an acid. While that acid may not dissolve your skin or burn through metal, it will certainly make you cry.
As a species, we have learned three tricks to dealing with the sharp flavors generated by raw alliums:
- We cook them. Cooking the alliums will release the chains of sugar that they use for energy into actual, tastable sugar, which we enjoy properly. It also breaks down the sufuric compounds into other flavorful compounds in a variety of ways depending on our cooking technique.
- We grow them carefully. If you can find some soil that doesn’t have any sulfur in it, then the plants can’t grab sulfur out of the soil. This will result in a sweet, inoffensive onion, such as the ones grown in and around Vidalia, Georgia. Georgians like to eat Vialia onions raw, because they can. Oh, they’ll say they just love the flavor, but I think mostly it’s to show the onions who’s boss.
- We are pig-headed. Then again, why go through all that trouble? Sometimes we convince ourselves that we really like the burning, limited range of raw onions or garlic, and just eat them like that. The plants are all, “B-but… millions of years of evolution to create a chemical weapons factory to discourage critters like you from eating us and you just do it anyways?” And then they start moping with the chiles and listening to Morrissey albums.
- Yellow, white, and red (a.k.a storage onions). Onions in their typical bulb form have a multi-layered cellular structure. When the outer layers lose moisture, they become papery. These are the onions that will make you cry when you cut them, because they store as much sulfur as they can get their roots on. Properly stored in a cool, dark, and dry place, they can last for several months. These are great as an aromatic base (such as in a soffritto), quickly caramelized for a mix of pungent and sweet extra flavor, or slow caramelized over several hours into the best little vegetable jam you can imagine.
- Spring. Spring onions are the same plant as storage onions, but harvested earlier in their life cycle. They have spent all their effort into getting into a form where they can collect energy, and not as much effort into actually storing that energy. Consequently, they are not made for long storage, and don’t quite have the depth of flavor that the storage onions do.
- Green. Also known as scallions. These are grown for their greens, and in many cases don’t even have bulbs. These are especially used raw or just wilted.
- Shallots. Shallots have a much sweeter flavor than your general storage onion will, and are a very nice for refining a dish that would otherwise use onions. These are really, really good quickly caramelized. They grow in a clustered bulb, kind of halfway between a garlic bulb and an onion bulb. They have the garlic’s clustering, but the onions layers.
- Garlic bulb. I’m going to lump a lot of varieties of garlic into one category here. Garlic grows as clustered cloves, rather than the shallot’s clustered layers. Raw, a clove of garlic has an aroma that is very simple, very direct, and very hard to get rid of. After handling raw garlic, it’s not going to come off easily even with soap and water, but if you rub your hands on some stainless steel, that will break down the scent and allow you to wash it off. Do not buy a stainless steel garlic scent remover gadget. Seriously. You can use a spoon, a sink, a pot, a dishwasher, or whatever you might have around the house that is stainless steel. If you have nothing of stainless steel in the home, you might want to re-think your priorities. In any case, raw garlic is the worst use of garlic. You can use it as an aromatic or you can slow roast it for best flavor. Don’t over-cook it if you are using as an aromatic; it cooks faster than onions, so add it later. If it browns, it’ll become bitter.
- Scapes (or garlic greens). Use these more or less like you would use green onions, as they are basically the garlic equivalent.
- Leeks. These are fairly wide and large green and white leaves that grow without a bulb. Wash carefully to remove the grit that works itself between the leaves while it grows. The white portions are more tender than the green tips. Cook well or they’ll be tough and fibrous.
- Elephant Garlic. These are the things that look like huuuge bulbs of garlic (hence the name), but are really a variety of leek bulbs. They are mild in flavor.