[Sca-cooks] beating egg whites

[Pixel, Queen of Cats]

It occurred to me, this weekend, while making up shortbread biscuit for
dinner, that nobody had posted as to the chemistry behind the beating of
egg whites. In case anybody still cares. ;-)

Basically, egg white is protein, yolk is fat. When you beat whites, you
are doing the same thing to them as you do to gluten when you knead
bread--forming long protein chains. The whisk also incorporates air into
the process, which is trapped by the framework of protein chains, and thus
you get foam. As fat does to gluten, so it does to egg whites--keeps the
proteins from sticking to each other. Soap does the same thing.

Perhaps, although someone who knows more about food chemistry than I do
could probably answer this better, the acid in the lemon juice or the
cream of tartar neutralizes any wandering alkalines in addition to helping
the proteins stick together.

Margaret FitzWilliam