Originally Posted by MollyGoat
It's a leavener nonetheless. Anything that makes a baked good rise is a leavening agent. Eggs are what's known as a "physical" leavener (as opposed to "chemical" leaveners like baking soda.)
I'm not arguing that eggs can not " be a leavener" I am trying to explain how they can serve 2 functions that contribute to the lightness of a cake (or something like a cake, im going to leave bread type things and other stuff out of this because I can only type so much).
The first function is that eggs can be agitated to incorporate air, such as a stiff egg white foam, lightly beaten whole egg, or creaming the eggs with other ingredients. This provides leavening because it adds air to the batter, and that air in some cases expands when heated and creates even more lightness.
The second function I'm talking about is the ability of eggs to trap gas bubbles (which could have come from chemical leavening, mechanical (physical) leavening, or steam) during baking. Eggs have this ability because when they are heated, they solidify and stay solid, this keeps the stucture of the cake, consisting of bubbles of gas surrounded by walls of batter, from collapsing in on itself, the egg protiens hold the bubble walls in shape when they solidify, and keep the gas from clumping together and rising to the top, and the batter will not fall and clump together in the oven because it is rigid.
for someone baking vegan products or trying to convert a non vegan recipe to be vegan, it is important to understand what functions eggs serve in differant types of products, and how they do it, then you can begin figuring out what type of egg replacer would be best suited to a particular recipe. eggs provide moisture which binds, emulsifing properties, foaming properties, structure holding properties, can trap air in batters when agitated, and can thicken sauces and custards. egg yolks can provide tenderizing fat too.
as far as saying "eggs are a leavener", I have never liked that statement. It implies that all you have to do is add more leavening and your cake will be fine. what you might end up with is an over-leavened cake. When a cake is overleavened too many bubbles are generated during baking, and they can clump together make bigger bubbles that rise and pop out of the surface of the cake leaving a very dense product behind, especially if the batter is so soft that it doesnt get rigid enough in the oven to hold its shape. also, eggs dont always provide leavening. Eggs are an ingredient in plenty of things that are dense and have no air bubbles, such as custards, hard and soft boiled eggs, egg noodles, pan cooked eggs (provided they are not beaten before being fried), and probably more than that.
So, I dont want to get in a silly argument of "eggs are a leavener" "no there not" "yes they are" Id rather save my arguments for the omnivores, but my point is trying to explain whats going on with the eggs, so we can figure out how to replace them in differant things, depending on the needed function.