What does salt do to an egg white foam?
That’s what reader Daniel wants to know. Daniel, let’s just say that adding salt to egg whites before you whip them is never a good idea. Why not? Well you remember the below post on how egg foams form. Agitation causes the little bunches of proteins in the white to unfold, at which point the individual molecules start to collect around air bubbles and bond with each other. If there’s salt in the mix that bonding process is slowed as the salt dissolves into its component parts — sodium and chloride — and those ions start to adhere to the bonding sites on the protein molecules, preventing the proteins from using those sites to bond with each other. The result is that the foam takes longer to whip up and is less stable when it finally does form.
The logical question then is: well, what if I added the salt later, as I would do with an acid to help keep the proteins from over-bonding and coagulating? Some bakers do that, however for my money acid and copper are more reliable — and less potentially destructive — foam protectors.
And the other question would be, why is there a tradition of adding salt to egg whites for whisking if it destabilises the foam? I wonder why people thought it was a good idea in the first place. (Personally, I don’t generally add anything – I just make sure the bowl is entirely grease-free.)
Hey Daniel!
Good question. It’s not that salt prevents foam from forming it just make a weaker foam, at least when it’s added early. Added later it probably does provide a little insurance against over-whipping, so maybe that’s how it got started. Then again there are a lot of kitchen myths out there! Who knows where some of them come from.
Thanks for a great question.
– Joe
Interesting. Thanks Joe. We’ve been working on financier recipes, for example, and even Eric Kayser’s recipes call for the egg whites to be whisked with a pinch of salt. Perhaps when you’re not making a strict meringue, for example, but instead adding flour, ground nuts and even BP, the lower stability isn’t so much of an issue?
(These financier recipes bring up another question for me too though – if you’re using BP, why rest the mix in the fridge? Surely the BP is activated, and loses its potency before you actually come to baking?)
Dan
Hey Dan!
That is interesting. It does depend on when you’re adding the salt of course. If it’s a little later in the whipping process it’s not a problem. Or maybe the idea is to thin the whites a little early on, in hopes that they’ll whip up more readily. I can’t say for sure. It could also just be habit…you never know and some kitchen myths die hard! Either way a little salt isn’t going to ruin an egg white foam. A slightly less stable foam will still perform well as long as you’re careful!
Love your follow-up question also. Mind if I answer that on the main blog? Others will be interested.
– Joe