Whipped egg foams are another one of those instances where the older the eggs are, the better (within reason of course). Why? Well because older eggs have runnier whites, and when egg whites are runny it's easier to put the hurt on the proteins they contain. Think of it like this: a whip cuts through a bowl of water with much more force than it does through a bowl of, say, honey. Which would you rather try to whip up into a foam? Older, room temperature whites are not only easier to work with, they whip higher.

The only problem with old eggs of course is that the yolk walls are thinner and so are more likely to rupture when you separate them, getting unwanted fat in your whites. A low temperature helps with that, but then if warm whites make better foam but cold yolks are better for separating, what the heck are you supposed to do? The answer: separate your old eggs right when they come out of the fridge, then let the whites come to room temperature before you start whipping. Sounds like a bit of a pain, and I suppose it is, but are you committed to that angel food cake or aren't you? Well?

So while it is true that whole eggs will make foams, it's also true, because of the fat they contain, that they'll never rise as high as all-white foams. Under the right conditions egg whites can be whipped up to about 8 times their original volume. With whole eggs you're doing well if you can do 3 times, and even then the foam they make won't last terribly long. However it will last long enough to be of some use in a thing like a flourless cake, where you want to lighten the consistency just enough to prevent it from being a chocolate brick. Though that does sound sort of appetizing...

...as in this flourless chocolate cake. Would you believe our farmer's market still has raspberries? No, neither would I. I bought these giants at the grocery store. In general I like my flourless chocolate cakes a bit firmer. In this case all I didn't have all the chocolate I needed on-hand. Usually I use a 50-50 mix of bittersweet and semisweet. For this one I had to use half milk chocolate (it was a rush project for one the wife's classrooms) so it turned out a little...goopy. Eh, they liked it. How bad can all that chocolate be? For a recipe comparable to the one I used, go to the Food Network site here:

www.foodnetwork.com/food/recipes/recipe/0,,FOOD_9936_30296,00.html

There is a popular myth that even a speck of egg yolk, butter or oil can make an egg white foam all but impossible to form. This is a, er...myth. For while you ought to go out of your way to prevent fat or other oily and/or soapy substances from coming in contact with your egg whites, a dot of errant yolk certainly won't hurt anything. But how does fat effect an egg white foam?

Well, you remember how I talked about how proteins form a reinforcing mesh around air bubbles. Part of the reason protein molecules collect so readily on the surfaces of those bubbles is because, like fat molecules, they have love-hate relationships with water. Some regions along their length love it (in other words, are hydrophilic) and others hate it (hydrophobic). The surface of an egg foam bubble is thus the perfect spot for them: they can stick their hydrophobic bits in the egg white, dangle their hydrophobic parts in the air, and bond to one another side-to-side in the bargain. Ahh...

But as I mentioned, fat molecules have both hydrophobic and hydrophilic parts too, and so are likewise attracted to bubble surfaces — where they compete with proteins for a spot. The difference of course is that unlike proteins, fats don't bond to each other side-to-side to form reinforcing networks. In fact, they only get in the way...keeping protein molecules from finding each other. Once the protein network is formed it's safe to expose fat molecules to it (which is why you can integrate a rich yolk and cheese mixture into a soufflé batter without destroying it). But until those proteins get a chance to do their bonding, fats should be denied an invitation to the party.

The frustrating thing about fiddling with proteins is that the same action that uncoils the things almost always re-coils them if you don't quit while you're ahead. It's this clenching action that causes custards to break, cooked meats to turn to rubber, and foams to collapse in a runny heap (albeit for different reasons). And the worst part is that once this protein clenching has happened, there's usually nothing you can do to reverse it.

Where egg whites are concerned, the point of no return occurs somewhere right after the stiff peak stage, when the protein molecules that were arranged in nice regular lattices...bonded elegantly in a mesh...cradling big fat bubbles of air...start to curl back up again. As this happens, bubbles pop as water molecules are squeezed out from between the proteins and the forces of surface tension once again take over. The egg white foam starts to turn grainy, then clumpy, then watery, at which point it's pretty much useless.

What to do about it? While nothing can ultimately protect an egg foam from too much whipping, there are a few steps you can take to broaden your margin of error. One of those is to employ a copper bowl, since copper ions do a remarkable job of plugging up the bonding sites on protein molecules, preventing them from bonding too readily and overcoagulating. The same thing works with silver if you happen to be a ward of Daddy Warbucks. Yet there are a couple of additives that work pretty well too. You can simply add copper in supplement form, which you can find at your friendly neighborhood health food store. Of course an easier option is acid, easily had in the form of vinegar, lemon juice or Cream of Tartar. Any will do a decent job of hobbling those bonding sites long enough to keep your foam from breaking down from overexertion.

That's of course assuming that nothing else goes wrong. Can anyone say "fat"?

The next stop on our Big Five Mixing Methods tour will be the Egg Foam Method. Of all the various mixing methods out there, the Egg Foam Method has the virtue of being the most direct, the simplest. For indeed, instead of spending time and effort to create the conditions most likely to produce gas bubbles (as with every other method), with the Egg Foam Method you simply whip them up yourself. The challenge then of course: to keep those bubbles from bursting.

The Egg Foam Method begins, unsurprisingly, with eggs. Usually just the whites, though it is possible to make egg foams using the yolks too (they don't fluff up as well, but more on the reasons for that later). The eggs are introduced to some sort of whipping device — a stand mixer, hand mixer, or whisk. Air begins to be incorporated and before long, voilà, ze foam. The next step is usually to introduce some form of acid stabilizer (cream of tartar, say) before the foam is folded into the other ingredients in the recipe.

What do those air bubbles do in the, er...whatever-it-is? Just as with all other mixing methods, they leaven (or "push up") the batter. Once again it's not expanding air that accomplishes the task. Air only expands by 20% or so in the heat of an oven. Rather it's the water in the batter that does it. As I mentioned last week, water expands to some 1400 times its original volume when it's converted to steam. The steam blows up the air bubbles and bingo, you've got leavening.

Interestingly it's the hand mixer, as opposed to one of the stand variety, that's the best tool for making egg foam, since it allows you to chase down every last little pocket of unwhipped white (my big ol' Viking mixer is terrible at egg whites). Of course you can do it by hand, but there are very few people out there with the forearm strength to whip up a mass of egg whites into peaks before some of the foam starts to collapse. I once knew a brawny Swede who could do it. That sweet old lady could have pimp-slapped a longshoreman unconscious. The rest of us mortals need machines.