Greenghost, maybe you know?
Eggwhites (primarily ovalbumin in composition) can be beaten because the ovalbumin protein partly unfolds under shear stress to form an excellent surfactant (it makes bubbles.)
Further, ovalbumin denatures nicely with a moderate amount of heat, and those beaten bubbles can, with the inclusion of a little starch or fiber, become structurally stable.
Both these properties are important to me, since I require a very low-carb diet. A low-carb diet means that if I want anything that looks like a baked good I have to rise it with beaten egg-whites and hold it up with insoluble fiber. Ergo, beaten egg-whites are the only thing that keeps me from being vegan.
Various polysaccharides work as a surfactant and make plenty of bubbles, but those bubbles seem to have no stability when cooked. I presume because being polysaccharides they do not denature.
I *think* this unfoldability is on account of ovalbumin being in the serapin protein family, but I don’t know.