Every time I try to whip egg whites, I seem to end up with the same problem. After a good bit of strenuous beating with the whisk, the egg whites finally reach the "firm peak" stage. I then go grab something (last night, it was the chili peppers to coat in egg), and right away the egg has separated into fluffy white peaks on top, and liquid on the bottom. What's going on? Is there a trick to keeping the egg white a uniform texture?
This is the nature of meringue: they will start to fall apart as soon as you stop whipping. There are a few tricks to help it hold longer, but in general you want to have EVERYTHING ready to go as soon as the meringue is whipped.
To help stabilize the meringue you can:
Now for WHY these tricks work:
I'm going to quote heavily from Harold McGee's "On Food and Cooking", as it does a wonderful job explaining meringues and other whipped egg whites:
Whisking unfolds these proteins, primarily globulins and ovotranferrin, which bond to each other and stabilize the bubble walls. Cooking will evaporate the water and unfold ovoalbumin, creating a rigid and permanent protein network.
However, the same proteins can ALSO destabilize the foam if they bond too tightly. "The protein network begins to collapse when too many of these bonds accumulate and the proteins cluster together too tightly" (page 102). In the case of egg proteins, one of the strongest bonds is a disulfide bond between the sulfur-containing amino acids, cysteine and methionine. Eggs contain copious quantities of these amino acids, which are why they produce such a potent stench when they spoil; the sulfur is converted to malodorous sulfur compounds, particularly hydrogen sulfide.
Copper, silver, and acids stabilize the egg foam by preventing the formation of these disulfide bonds. To quote Harold McGee (page 103):
McGee also notes that silver has the same property of inhibiting disulfide bonding. Acid achieves the same goal of reducing disulfide bonding, but works slightly differently:
Hard to say what's going on exactly, but there are a few things you can do.
That's about it.