The Incredible, Edible Egg! Part 2
The egg white is made up of four distinct layers. These layers differ primarily in consistency. Two thin layers alternate with two thick layers. The white accounts for about two- thirds of the total liquid weight of the egg and more than half its protein as well as the B vitamins riboflavin and niacin. Due to changes in its proteins, the egg white becomes thinner with age. This is why older eggs spread out farther in the pan when cracked.
Egg whites form foam when beaten, increasing in volume up to eight times through the incorporation of air. The white, stringy looking stands in the egg white are called the chalaza. These act to hold the yolk in place inside the white and have no effect on the taste or cooking properties of the egg. Some people like to remove these but it is not necessary.
The inner and outer shell membranes are just inside the shell. These membranes surround the albumin and the air space is formed between them once air begins to enter through the pores. The vitelline or yolk membrane protects the yolk from breakage and holds it in place. This membrane weakens somewhat as the egg ages.
The egg yolk or yellow makes up the remaining third of the liquid weight of the egg. Although slightly less than half the protein in eggs come from the yolk, it contains all of the fat. With the exception of the B vitamins, the yolk also contains most of the vitamins in eggs. Egg yolk is one of the few unfortified foods that supply vitamin D. Likewise, most of the minerals in eggs come from the yolk. The yolk is responsible for the valuable emulsifying properties so important in cooking. Double-yolked eggs are sometimes laid by young birds in which the egg production cycle is not yet adjusted. Genetics is also a factor in the formation of double yolks and some birds continue to produce them throughout life. The yolk is where the embryo forms in fertilized eggs.
Cautions against eating raw eggs are due to the fact that eggs may contain bacteria like Salmonella enteritidis, which can cause food poisoning. Although eggs are washed and sanitized prior to packaging for sale, bacteria sometimes enter through the pores in the shell before they are washed. Contamination may also arise from bacteria present within the ovary or oviduct of the chicken before egg formation. Although scientists estimate that only one in 20,000 eggs actually contain Salmonella enteritidis, you never know if the egg you are eating happens to be the one that's contaminated. Cracked eggs are more prone to contamination since the cracks allow bacteria easy entry. Consequently, it is best to examine a carton of eggs at the store to be sure you don't purchase cracked eggs.
Eggs contain elevated cholesterol levels, and nutritionists have been telling us for years that a diet which is high in cholesterol can result in increasing the level of cholesterol in your bloodstream. One large egg contains approximately 215 milligrams (mg) of cholesterol which is entirely located in the yolk. The generally recommended limit of dietary cholesterol intake is 350 mg a day. As you can see, it is recommended that we only eat two eggs a day, however if you love eggs but would like to avoid the extra cholesterol, simply utilize the egg whites as they contain no cholesterol. Egg white omelets are now a standard feature of almost every breakfast and brunch restaurant menu.
Eggs are healthful, nutritious, and delicious. Eaten in moderation to prevent excessive cholesterol build-up, they are a wonderful addition to any dietary plan!