What is an egg
Because the body temperature of a hen is approximately 106º F, eggs are very warm at the time they are laid. The temperature of the air is usually much lower than 106º F, and the egg cools to the temperature of its surroundings. As cooling takes place, the contents of the egg contract more than does the shell of the egg. This creates a vacuum and air is drawn through the pores of the egg.DOWNLOAD REFERAT
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As a result, an air cell forms at the large end of the egg. While the embryo is growing, the shell membranes surround and contain the white or albumen of the egg. The albumen provides the liquid medium in which the embryo develops, and it also contains a large amount of the protein necessary for proper development.
In a fresh egg, we can see white cords attached to the yolk sac. These two cords, called chalazae, are made of twisted strands of mucin fibers that are a special form of protein. The chalazae hold the yolk in the center of the egg.
The yolk is the source of food for the embryo and contains all the fat in the egg. The small white spot on the yolk is called the germinal disc. The germinal disc is where the female's genetic material is found.
How recently an egg was laid has a bearing on its freshness but is only one of many factors. The temperature at which it is held, the humidity and the handling all play their part. These variables are so important that an egg one week old, held under ideal conditions, can be fresher than an egg left at room temperature for one day. The ideal conditions are temperatures that don't go above 40ºF. (4ºC.) and a relative humidity of 70 to 80%.
Proper handling means prompt gathering, washing and oiling of the eggs within a few hours after laying. Most commercially produced eggs reach supermarkets within a few days of leaving the laying house. If the market and the buyer handle them properly, they will still be fresh when they reach the table. « mai multe referate din Engleza