White of egg is called albumen . Albumen coagulates at 134° to 160° F, so cook eggs at lower temperatures. Eggs cooked at high temperature or in boiled water for longer times are tough and will change its color due to oxidation. Yellow part or yolk is rich in iron and magnesium.
How to know if an egg is fresh ? Buy longer expiration date eggs, not cracked and make sure are proper refrigerated, if you are not sure follow the methods
An egg placed in a cup of cold water should sink.
Look in to a light trough an egg and the inside should be clear
Eggs are a complex food and have all the elements necessary for the support of the body.
A pound of eggs equal in nutritive value to a pound of beef. Eggs being rich in proteins serve as a valuable substitute for meat at a lower costs.
Eggs need to be refrigerated or pasteurized to hold for days. shell is made out of calcium and its pors absorb air into the egg. In less than 24 hours an egg starts is decomposition at room temperature.
Pasteurized eggs has their pors closed by dipping the egg in wax or other solutions. Liquid eggs are pasteurized by heat. Kids and elderly should consume only pasteurized eggs.