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I've talked quite a bit about both egg yolks and egg whites, but I've never really talked about how to separate them from each other. It's time to take care of that.

In general terms, the egg has four separate components. It has a shell, a yolk, a white and a chalazae. The chalazae is a rope-like structure that attached the yolk to the white, and helps the yolk stay centered in the egg. I make a point of mentioning it here because it is not actually part of the yolk or the white, and you will encounter it when separating eggs.

Before we get into the heart of this tutorial, we need to get set up. You will need three non-reactive bowls, set up in a row. By non-reactive, I mean glass or stainless steel. Don't use aluminum or plastic bowls. With aluminum you run the risk of adding off colors and/or flavors to the eggs. Plastics are bad too because the molecular structure of plastic is too close to that of fats. They are so close in fact, that plastic often bonds to fats, and that bond can remain for several washings. If your egg whites are stored in a plastic bowl, they run the risk of picking up fats that were previously stored there, which will render them unsuitable for whipping later.

I also lay out a paper towel, or sometimes a sheet of wax paper, next to the bowls. When you crack eggs, some of the white will start to leak between where ever you cracked it and the bowl. This means a messy counter, especially with a lot of eggs. The paper towel makes it easier to clean up later, though you will still want to wipe the counter under the towel when you're done. The towel also gives me a place to store used egg shells while I'm working. When I'm done, I just wrap up the shells in the paper towel and carry them to the trash can.



One of the most important parts of separating an egg is cracking the shell properly. If you hit the shell too hard, it will shatter into pieces. If you don't hit it hard enough, it won't really open. It's something that takes practice, but you need to crack the egg just enough so that it will open into two halves, roughly the same size. I often will hit an egg lightly against the counter, and then rotate it in my hand and hit it again. After two or three hits, it generally opens pretty easily.



This is when we actually start separating. I have seen many a tool for this sort of thing, and I'm happy to tell you that you don't need any of them. The only tools you need are already right in front of you: your hands. Some people use the egg shells as tools, and that method is perfectly acceptable. I find it tedious, and so I stick with my hands. I will, however, cover both methods.

Hold the egg above the center bowl and remove the upper shell. Some of the white will immediately spill into the bowl below it. The goal is to get as much of the white into that center bowl as possible, without getting any of the yolk into it. The fresher the egg, the more easily the two will separate from each other. I mentioned the chalazae before. It doesn't really matter where that part goes, so don't worry about it. I mention it again because some people will wonder what the heck to do with it. Don't worry about it, it's nothing.

To separate the egg, just dump the contents of that bottom shell into my other hand, leaving small cracks between my fingers that the white can slip through, but not the yolk. If you're using the shell method, you will carefully pour the yolk back and forth between the two halves of the shell, being careful not to let the edges of the shell cut through the yolk. This is exactly why I don't like the shell method; your hands will likely have far fewer jagged edges (hopefully none). I've also found the shell method to take too long for my tastes. After a couple of passes, the white will usually fall into the center bowl, leaving nothing but yolk inside the shell. Inspect the yolk. If there is any blood in it (and sometimes there will be), throw the yolk out. Believe me, you don't want it. If it's clean, go ahead and dump the yolk into one of the side bowls and discard the shell.





This part is important. Inspect the white in the center bowl carefully. There should be no yolk in it. If even a speck of yolk made it to the center bowl, discard the white and clean the bowl using soap and hot water. Even a speck of yolk will render egg whites unsuitable for whipping. If you notice while you're separating that the yolk has broken, dump anything that's left of it into your yolk bowl. Any remaining whites will do far less damage to the yolks than the yolks will do to the whites. Also, inspect the white for blood. If there is any, throw the white out. Once you've decided that the white in the center bowl is clean, go ahead and dump it into the other bowl that doesn't contain yolks.



At this point, you will have a separated egg! Many bakers will actually separate two at a time into the middle bowl, before dumping it into the whites bowl. You can just stick with one at a time until you get practiced. Most (but not all) recipes that call for separated eggs will call for many, so go ahead and separate the others. Keep the yolks in one bowl and the whites in another. If ever a piece of yolk gets into the center bowl, make sure to wash it before continuing. And yes, soap is the only way to be absolutely certain that there is no more fat in the bowl.

Did your recipe only call for egg yolks? If you're making ice cream or cheesecake, it might have. That leaves you with a whole mess of egg whites. These can be frozen for up to a month, maybe even two, and then thawed when you're ready for them. I've seen many a cook freeze them in ice cube containers, and once frozen they move the cubes to a zip-top bag (always with the date on it). This method is fine by me, so long as the ice cube tray has never been used to store anything with fat in it (you should probably be okay there). To thaw, move the whites to the refrigerator for a day. This should give them plenty of time to thaw properly and safely.

Did your recipe only call for egg whites? If you're making angel food cake or meringue, it probably did. If you're planning on putting together such a recipe, I would suggest finding another one that uses yolks, and making that at the same time. I have safely stored yolks in the refrigerator overnight, but I don't trust them after that. If you can't use them within 24 hours, throw them out. They don't store nearly as well as the whites.

Hopefully I have given you enough information to properly separate eggs. It may look intimidating, but if you do it enough, it will become second nature to you. Go ahead and whip up an angel food cake or a batch of ice cream. Get some practice separating some eggs. It's not nearly as complex as you'd think, and it's an extremely valuable skill to have.

Labels: baking, cooking, eggs, tutorials

The first time Alton Brown referred to a regular old egg as a "chicken egg", I must say I was amused by it. I was so amused in fact, that I began referring to them the same way myself. I remember the first time I did so on the Good Eats Fan Page Message Board, somebody noted that they had been wondering why Alton Brown specified a chicken egg, and why I did so too. At the time, I think I joked that I wanted to make sure people didn't think I was referring to a quail egg. By that point I had had some small experience with them myself, and I argued jokingly that I wasn't the only one.

Today when I investigated a small spike in my stats, I found a story on Digg that was similar to my post on chocolate chip cookies. One person linked to my article in the comments, and somebody else joked about me using chicken eggs. When I read that, I decided that it was time to write a little bit about one of my favorite ingredients: the chicken egg.

Unless a recipe with eggs specifies otherwise, it probably calls for large chicken eggs. In most supermarkets that I have been in, I have also seen "extra large", "medium" and sometimes "small". While my focus is going to be on large eggs, let me give you the breakdown on egg sizing, according to my notes from bakeshop in cooking school:

Jumbo         30 oz per dozen (by weight)
Extra Large   27 oz per dozen (by weight)
Large         24 oz per dozen (by weight)
Medium        21 oz per dozen (by weight)
Small         18 oz per dozen (by weight)
Pee Wee       15 oz per dozen (by weight)

That means that the large egg averages about 2 oz. Of that 2 oz, approximately 1 oz is egg white, 2/3 oz is yolk, and the rest of it is shell. Now before you bread out your scales and start trying to prove anything, let me remind you of a few things. First of all, these are approximations and averages. Every egg is different, and every egg producer is different. When I buy my eggs at CostCo, they tend to all be pretty much the same size. When I buy my eggs from my favorite supermarket, they tend to differ radically in size, but I have little doubt that one dozen of them weighs about 24 oz. Obviously, since I prefer a little more consistency in my cooking, I try to buy my eggs from CostCo when possible.

Speaking of their eggs, something else important to note is that while they are cheaper and more consistently sized, theirs tend to be a brown color, while the norm at my supermarket is white. You can buy brown at my supermarket, but at a premium. When I lived in New Hampshire, brown seemed to be the norm. Obviously, this is a very regional thing. As far as I know (and I don't believe anyone has definitively proven otherwise), there is absolutely no difference between the contents of brown vs white eggs. They taste the same to me, and as I'm sure you've guessed, I pay a lot of attention to things like taste. But I have noticed that the brown eggs that I used seem to have a sturdier shell. And since I tend to use these a lot, I've gotten used to how they crack. The white eggs feel funny to me now when I crack them, because the shell is so thin in comparison. But I can't say that this is always the case.

Something else that I noticed in New Hampshire was that all of the eggs were "Grade A". When I mentioned this to my friends out there, they all gave me kind of a "well, duh" response. Of course they were Grade A. It's not like they'd be selling Grade B, and what's this Grade AA thing that I keep talking about? Well, I seem to have the upper hand on this one, since I have never seen anything lower than Grade AA sold in Utah. This baffles me because I have also never seen an egg farm in Utah (though I know they're here), and I drove by one on the way to school in New Hampshire. Obviously it's not a question of distance.

What is the difference between the different grades? That's a good question, and one with many answers. An egg that is Graded AA is pretty fresh. The way to keep an egg fresh is to store it at the right tempurature, ideally 36F. If you can manage to store your eggs at exactly this tempurature, they will last for a good five weeks. During this time, they will gradually drop from Grade AA to Grade A to Grade B. Any of these grades is perfectly edible, but at five weeks, you probably want to toss any that are left. As the eggs age and pass through these grades, they will undergo several physical changes. For instance, eggs have an air gap. At Grade AA, that gap will be about 1/8-inch. As it drops to Grade A, that gap will increase to about 3/16-inch. By the time it hits Grade B, that gap will have increased to somewhere around 3/8-inch.

During this time, the yolk will also begin to steal a little moisture from the white. This is very valuable knowledge for a couple of reasons. Once you have cracked an egg, you can tell roughly what grade an egg is after a little practice. If you crack the egg onto a level surface, you can look at how high the yolk and white is. A Grade AA egg will have a very firm yolk and white, causing it to stand pretty tall. As the yolk leeches moisture from the white, the structural integrity of both will decrease, and the egg won't stand as tall.

This means something else important. The higher the grade of the egg, the easier it is to seperate, because both the yolk and the white have a lot of structural integrity. But this also means that the older the egg is, the easier it is to mix into things. Because of this, Grade B eggs are actually eaiser for bakers to use. This is not to say that your local bakery is using Grade B eggs, but they might be. If they are, I wouldn't worry. If they decide to drop below that, I would.

Eggs serve a lot of purposes in cooking. For instance, while the white is mostly water, the rest of it is a protein called albumin. This protein can be whipped, which is a topic for a whole other post. It is also used sometimes in stocks and broths to clarify the liquid, and is in fact a key component in making a very clear and flavorful soup called consomme for this very reason. The yolk contains fat, water, protein and a small amount of cholesterol. The jury is still out on how healthful the yolk really is, but it does have its culinary uses. One very handy application is as an emulsifier. In a nutshell, emulsification is a process which helps force a stable mixture of two substances that would normally repel each other. Without this power, mayonnaise would be a very difficult recipe to put together.

Since an egg contains somewhere about 73% water, it can also bring a good bit of moisture to the party. Because of the emulsification power of the yolk and the structural power of the white, things like custards are made possible. Custards generally contain at least one egg, some kind of dairy (for additional moisture and/or protein), and a certain amount of fat (usually butterfat). This ranges from stirred custards (such as lemon curd) to baked custards (such as cheesecake).

Eggs also offer a lot of flavor. While I don't generally like eating eggs on their own, I can't deny that I love a lot of breads that are enriched with eggs. Does challah need to have all those eggs for structure? I doubt it. But they do add an excellent flavor that really defines the bread. Speaking of challah, I have never seen a recipe for it that doesn't call for an egg wash before baking. While the dough itself doesn't need any help with color, the egg wash does deepen the color even more, often making it a little brighter and always adding that characteristic shine.

This eggwash is applied to a lot of baked goods for a lot of other reasons too. I have baked many a pie using an egg wash to help it hold onto a generous sprinkling of coarse sugar. Protein is nature's glue, and eggs have plenty of it. Egg washes are also used by some bakers to stick pieces of dough together, for various artistic effects. While I'm at it, I might as well touch on the fact that since the yolk contains some fat, it can also be used for some shortening of gluten strands, though I'm sure much of the water in the eggs helps out with the formation of gluten enough to cancel that out a little. And of course, since egg whites can be whipped, they can be used for leavening.

So that's a nice little overview of eggs for those of you who are interested. If you really want to get into all sorts of nifty historical and scientific facts about eggs, I recommend On Food and Cooking by Harold McGee for additional reading.

Labels: baking, cooking, eggs