1. Explain the structure of an egg
2. To grade and list the selection of an egg
3. State the uses of eggs in cooking
Eggs are one of the most essential foods used in cooking. The eggs of hen are most commonly used. Eggs of turkey, guinea fowl, ducks and geese are also used. It is a complete diet providing all the protein, fat, vitamins and essential minerals. It provides moisture, structure and richness to the products.
The Egg is made of three parts
1. Egg shell: 12 per cent
2. Egg white: 58 per cent
3. Egg yolk: 30 per cent ,
This is made of calcium carbonate (94 per cent) with traces of magnesium carbonate, calcium and magnesium phosphate, 4.5 per cent organic matter and 1.5 per cent water. This is very porous and light can pass through it. Due to the porous nature absorption and evaporation of air or liquid is possible. Covering the shell is a dull protective coat called the bloom or the cuticle.
Egg white: The liquid content inside the egg is separated from the shell with the help of two thin membranes which are made of keratin and mucin which later give way to an air sac. Egg white is made of thin egg white and thick egg white. Usually the thin egg white constitutes about 20 to 25 per cent of the total egg white. The thin and thick egg white is distributed in three layers, covering the egg yolk is a layer of thin egg white, followed by thick egg white and then by thin egg white.
Egg yolk: Surrounding the egg yolk is a thick membrane called the vitelline membrane or yolk sac. Extending the vitelline membrane on opposite sides are two Chalazae that helps to hold the yolk in the centre. Egg yolk contains lecithin and cholesterol.
Composition and nutritive value of egg:
Water – 75 per cent
Protein – 12-14 per cent
Fat – 10-12 per cent
Mineral matter – 11 per cent
Separately the egg white alone contains:
Water – 88 per cent
Protein – 11 percent
Traces of fat
Mineral water – 0.6 per cent
Egg yolk contains:
Water – 50 per cent
Protein – 6 per cent
Fat – 31 per cent
Mineral water – 1.7 per cent
Selection of an egg
The selection of an egg can be done in one of the following methods
1. Floating or buoyancy method
2. Candling method
Floating or buoyancy method: This is done by placing the egg in water. Fresh egg is heavy and settles down to the bottom whereas an old egg floats. This shows that the egg is becoming rotten.
Candling method: This is followed to know the quality of the egg. The egg is held against a strong light. As light passes through an egg, if the egg yolk remains suspended in the centre then it is considered to be fresh.
While selecting eggs it should be
1. Clean, sound and odour free
2. Purchase only the quantity of eggs required for two weeks.
Storing of eggs
1. It should be refrigerated at 2°C and can be kept for three to four weeks.
2. It should be kept away from strong smelling food
3. Store always the pointed side down
4. Should not be exposed to a temperature above 55 F as it shortens the keeping quality of the egg.
Grading of an egg
Eggs are usually graded depending on the size and weight.
|Jumbo\Extra Large||60g and above|
Source: Indian Standard Institution, New Delhi, India
Uses of egg
1. Provides good nutrition to the product
2. Enriches the product
3. Used as a raising agent
4. Used as a thickening agent
5. Used as a binding agent
6. Used for coating products to form a crispy crust
7. Used as a clarifying agent
8. Used in garnishing and decorating products