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.
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. Specifically, you can add various substances to the mixture that preemptively plug up the proteins’ bonding sites. Copper ions serve that purpose very nicely, which is why more than a few egg white whippers like to use copper bowls.
On the less expensive side of the spectrum are some simple additives. Copper ions can be had in the form of a dietary supplement, available at your friendly neighborhood health food store. A somewhat less effective yet much more readily available option is acid in the form of vinegar, lemon juice or cream of tartar. Acids don’t affect the proteins’ bonding sites directly, though by changing the pH of the mixture they increase the number of free hydrogen molecules, which gunk up the works quite nicely.
So you see there are a variety of good options available for keeping your egg white foam from breaking down as a result of overexertion. But then over-whipping is just one of a number of factors that can adversely affect a foam. Can anyone say “fat”?