In a recipe, when eggs are called for the are usually hen eggs and mostly commonly large or extra-large in size. The most common hen egg-shell colors are brown or white. There is no nutritional or flavor difference between white and brown eggs. The color comes from different breeds of hens . Hens with white feathers and white ear lobes lay white eggs while hens with red feathers and red lobes lay brown eggs. Of course chickens have ears! How else would they hear you calling, " Here chicky, chicky".
Average hen eggs weigh about 2 ounces;the white is 1 ounce and the yolk about 2/3 ounce and the shell is 1/6 ounce. Yes- I just did math! If a recipe calls for a large egg, then you will be using a 2 ounce egg. X-large eggs weigh 2.25 ounces, medium eggs weigh 1.75 ounces and jumbo eggs weigh 2.50 ounces each. So, let's think about this...that would mean that 1 large egg would be equivalent to 1 medium egg or 1 extra-large egg. That's pretty easy to figure out but rarely do baking recipes call for only 1 egg.
Now we'll see where size matters! 3 large eggs would be equivalent to 4 medium size eggs and 3 large eggs would be equivalent to 2 jumbo or 4 small eggs... see where I am going with this? If you use eggs of different sizes, adjust the number in the recipe accordingly.
So why am I giving you a lesson in egg size, because eggs are one of the two structural materials used in baking (flour is the other) that are indispensable in pastry. Eggs can be used in an endless list of wonderful creations. When combined with flour, eggs create the framework that support and traps air in cake batters; egg whites for meringues, to thicken custards and put the beautiful golden glaze on breads and pastries, and on and on. There is a natural emulsifier in eggs that aid in making smoother batters and creams.
Proper storage of eggs is most important. Eggs will keep up to 4 weeks if stored at a temperature of below 40 degrees. While most baking recipes call for room temperature eggs, eggs will age more in one day left a room temperature than in one week in the refrigerator... so take only what you will need for the your days baking. Now having said that, Ina Garten (The Barefoot Contessa) leaves eggs out overnight for baking. She says "when you beat eggs and sugar at room temperature it incorporates the ingredients better and makes a huge difference." On the other hand Julia Child said this about eggs, "It behooves us to choose eggs carefully and to treat them right. Because at room temperature they make a warm and comfortable home for evil bacteria, always buy refrigerated eggs, never buy cracked or dirty eggs, always bring your eggs home in a refrigerated container, and keep eggs chilled until the moment you are to use them."
I do something in between Ina and Julia. I allow eggs to reach room temperature for the same amount of time it takes butter to reach room temperature. When the butter is soft, then the eggs are ready. Remember safety first when using eggs, keep your surface and hands eggs free. No evil bacteria! Now get Cracking!
Eggs - a leavener in cakes and breads and add structure to other baked goods.