Structure and Composition of an Egg
Eggs are one of the most nutritious and versatile foods in the kitchen are served on their own, and used as an ingredient in many dishes starting from soup to desserts. It provides texture, structure, flavor, and moisture as well as nutrition. Eggs can be brown or white; color does not affect quality or flavor but depends on the breed of the hen.
The egg is composed of a Shell, Membrane, Aircell, Egg White, Egg Yolk, and Chalaza. The egg white forms 2/3rd of the whole egg and the yolk forms 1/3rd.
- The Shell the outer covering of the egg, is either white or brown.
- It is the outer hard covering of the egg and is made up of Calcium, Magnesium carbonate, and Calcium phosphate.
- The shell gives shape to the egg and holds the inner contents.
- The shell contains thousands of pores that allow CO2 and moisture to escape, as well as air to enter.
- The shell is covered by a cuticle membrane or Bloom and should not be washed.
- The bloom acts as a protective covering blocking the pores and prevents moisture loss and bacterial contamination.
- When eggs are washed before going to the market, the cuticle is removed.
- To protect the egg, the washed eggs are coated with a thin film of edible oil.
- The color of the shell does not affect the quality, cooking properties, or nutritive value of the egg, the color of the shell is normally determined by the breed of chicken.
- A membrane lines the shell and forms an air cell at the large end of the egg.
- The mother nature has worked very hard to create the right package for the contents of the egg.
- Beneath the shell, there are two semi-permeable membranes – the outer and the inner.
- These membranes act as a protective layer in case the shell cracks.
- On one side of the egg (broader), both these membranes separate to form an air cell.
- This is formed by contraction of the contents as soon as the egg is laid, due to the difference in the outside temperature.
4. Egg white
- It has 1/8th part of the protein, which is called albumin; the remaining being water.
- The egg white consists of three parts – the outer thin albumen, the middle thick albumin, and the inner thin albumin.
- The white is clear and soluble when raw and white and firm when coagulated.
- Albumin in the egg white is valued by the chefs for its ability to hold air when beaten.
5. Egg yolk
- The yolk is the unfertilized embryo in the egg, yellow.
- The yolk is separated from the white by a membrane called the vitelline membrane.
- This membrane prevents the mix of both yolk and white. 1/6th parts of the egg yolk contains proteins, 1/3rd of fat, and the rest of water, Vitamins, and minerals like Calcium, Phosphorus, Iron, etc.
- The yolk is held centered in the egg by the Chalazae and these are the two white strands that are present when the egg is broken.
- The yolk is high in fat and protein and contains iron.
- A Large yolk has around 59 calories.
- The yolk is valued for the richness and texture that it provides in both cooking and baking.
- The egg is kept in position at the center of the egg with the help of the chalaza.
- It has a thick-cord-like appearance and is composed of proteins.
- This chord-like structure may have to be strained while making custards.
- The function of the chalazae is to hold the yolk in place.
- In baking, the chalazae are sometimes removed to ensure a uniform texture.
Composition of egg
|Parts of Egg
Nutritional Value of Egg:
The nutritional value of eggs varies with their size; it is not an important factor in judging their quality. Larger eggs, of course, have more food value than small ones. A single large egg provides 6.5 grams of protein or about 13% of the recommended daily intake for adults, as well as 80 calories and a good amount of iron, phosphorus, thiamine, and vitamins like A, D, E, and K. The disadvantage of the egg as a staple diet is its high cholesterol content.