Category: Pastry

Old is Gold

Reader Jay writes:

When you were talking about macarons, you said that old egg whites are better. Does the rule hold true for floating islands?

It does. Older eggs are better when it comes to making any sort of foam. Why? Simply 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. The result is that older whites are not only easier to whip, they whip up higher.

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What about plastic bowls?

I’ve heard you can’t make a decent egg white foam in them.

…writes reader Owen. That’s another well-worn myth in the world of foams: that it’s impossible to whip up a good foam in a plastic bowl, or using plastic implements. The logic is that because plastics are so similar chemically to fats and soaps, they tend to hang on to trace amounts of them, foiling future attempts at foamery. There’s some truth in this. Plastic, fat and soap all share certain structural similarities. It’s also true that they tend to want to hang on to one another when they’re in close proximity, as anyone who’s ever tried to wash out a plastic salad bowl coated with oil can attest (it takes lots of soap and scrubbing, and even then you probably can’t get rid of it all). But unless the bowl in question is actually greasy to the touch, those minute amounts of fat won’t adversely affect the foam.

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Whisk It

This week, for reasons that are surely clear, I found myself wondering when the whisk was invented. For a clue to that I started checking into the history of egg foams generally. I found that while people have been eating eggs forever, and binding ingredients with them for at least 2,500 years, egg foams haven’t […]

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On Whole Egg Foams

Reader Clay writes:

I’ve whipped whole eggs to a pretty impressive volume, which is why I’ve always been skeptical of the claim that fat ruins foams.

True enough, Clay. However while whole eggs will make foams, they’ll never rise as high or last as long 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 will only hold up for a few minutes on its own. However a whole egg foam 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 baking up into a chocolate brick. Though I suppose even a brick can be good if it’s made of chocolate, yes?.

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What does sugar add to an egg white foam?

Reader Allison writes:

Could you explain how sugar effects [the egg white foam] equation? I know that meringue I make with a higher sugar content holds longer for me (in addition to Italian meringue that holds even longer.) It seems to stabilize it, but I would love to know more about the science.

That’s a really interesting question. As soon as sugar hits the watery egg white, assuming you’re not adding too much or too much at one time, the crystals begin to dissolve. As they do so they combine with the water to make a syrup. The more sugar, the denser the syrup, and it surrounds the protein-reinforced bubbles, creating a sort of cushion in the spaces between the bubbles. Think of the sugar molecules like packing peanuts among a bunch of glass Christmas ornaments in a shipping crate. That’s pretty much what they are.

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Fat: The Foam Foiler

There is a popular myth which holds that even a speck of egg yolk, butter or oil can make an egg white foam all but impossible to form. This is, um…a myth. Sure, you ought to go out of your way to prevent fat or other oily and/or soapy substances from coming in contact with […]

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The Clenching Fist

The frustrating thing about fiddling with egg white proteins is that the same whipping action that uncoils them will cause them to bunch and clump if you don’t quit while you’re ahead. The point of no return occurs somewhere right after the stiff peak stage, when the proteins that were arranged in nice regular lattices, bonded elegantly, cradling big fat bubbles of air…start to lose their mojo.

What happens? In a nutshell, the excess agitation causes the protein molecules to bond excessively to their neighbors and gather together in masses (coagulate). As this happens water molecules are squeezed out from between them and the forces of surface tension start to take over again. The bubbles start to pop. The foam starts to turn grainy, then clumpy, then watery, at which point it’s pretty much useless.

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Let’s Talk Foam

What’s a foam but a bunch of bubbles? Masses of air surrounded by thin walls of liquid. The shape of a bubble is a factor of surface tension, i.e. the pull that the water molecules that make up the wall exert upon one another. That pull causes the wall to reduce itself into the most […]

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