Sunday, December 27, 2009

Diana Ross, Daryl Hannah, and Your Meringue

Dear Tricia, The meringue on my key lime pie always weeps. Why does that keep happening?

I'm going to go back to one of my older blogs about egg whites and re-teach it here today because this is an email I frequently receive. Plus the original blog entry was really about why you add cream of tartar to play dough, so it might have been a little round-about. Before we begin, I want to point out to the non-bakers that meringue is a fluffy topping made out of egg whites and sugar. You whip them up until the egg whites turn from goopy clear stuff into a billowing cloud of solid white awesomeness. You just beat the egg whites and sugar together, right? No, not exactly.
Its common for meringues to "weep", or start to fall and leak out water. This is because when you whip egg whites, you're "coagulating" the protein in the eggs, which is a fancy pants term for protein bonding with other protein. When the proteins bond together, they hold in all the water that is floating around the meringue. If the proteins aren't doing that properly, the water will find a way to leak out, or "weep."
Under a microscope, egg whites are tiny strands of tightly wound protein. They look like a big mess of little corkscrew-y, spring-y shapes. Actually, they look a lot like Diana Ross' hair, post 1980. In order to get the egg whites to expand and turn into a fluffy meringue, you have to get them to straighten out. When they're fully expanded, they'll look like long waves of protein, triple the size of the corkscrew ones. If we're comparing apples to apples, the fully expanded protein will be shaped more like Daryl Hannah's mermaid hair in "Splash," all long and loose and wavy. If Daryl Hannah's mermaid hair is going to hold in water and actually remain stable, there are a few things you have to do:

1. Add about a half teaspoon of cream of tartar while you begin beating the eggs. Cream of tartar is like hair spray for Darryl Hannah's hair. If the proteins are bonding with all the other proteins, cream of tartar will make sure they stay bonded.*

2. Use room temperature eggs. Egg whites can be like demanding Hollywood actors: they have all their requests for how big they want their trailer, what kind of food they'll eat, who their co workers are, before they can do their job the best way they know how. Egg whites demand to be room temperature before they'll whip up into a meringue. It works better than using cold whites, so let them come to room temperature before you start whipping them. And no, leaving the egg whites out won't make you sick. A lot of bakeries, if they know what they're doing, leave egg whites out all the time for this exact reason.

3. Don't just turn the mixer on high and expect the whites to instantly fluff up. You have to gently persuade the proteins to unwind. Imagine trying to style Diana Ross' hair into Daryl Hannah's hair: you wouldn't just put a comb in at her scalp and pull, would you? No, that would probably break some of her hair off. Protein will also break if you just start whipping it as hard as you can. Start off by turning the speed on low for a few minutes. Let the whites loosen up a little and then turn it up to medium for a few minutes. Then move into high speed to finish off.

4. Don't dump all the sugar in at the beginning. As if trying to get the proteins to coagulate isn't hard enough, you're adding an extra ingredient to it that can get in the way. After you turn the mixer speed up to medium, wait for the eggs to start to get foamy. Then, and only then can you start to slooooowly add the sugar. How slow? You want to still be adding sugar to it right before the meringue is finished. This just makes sure that while the proteins are bonding with each other, the sugar doesn't interfere too much.

So, to summarize, be gentle with the egg whites, keep them at room temperature, and don't dump the sugar in at once. Got it? Avoid being rough, cold, and dumpy. In meringues and in life.

*Harold McGee's book, "On Food and Cooking," (also known as my Bible) recommends adding 1/16 teaspoon of cream of tartar per egg white.

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