Biology of Eggs

Egg Structure

• An egg consists of three main parts: shell, egg white, and egg yolk.
• The outer eggshell is primarily made of calcium carbonate (CaCO3).
• The two membranes are made partly of keratin and provide defense against bacterial invasion.

Egg White (Albumen)

• The inner thick white (chalaziferous layer) is a dense, matted layer.
• Egg white contains about 90% water and 10% protein.
• It consists of several proteins, including ovalbumin, ovotransferrin, ovomucoid, and ovoglobulin.

Egg Yolk

• The yolk contains less water and protein than the white, some fat, and most of the vitamins.
• The major proteins in egg yolk are lipoproteins, including livetin, lipovitellin, and phosvitin.

Protein Content of an Egg

• Protein content of an egg accounts for about 12.6% by weight of the edible portion.
• Egg contains all essential amino acids, including leucine.

Types of Proteins

• Ovalbumin: an almost spherical glycophosphoprotein, the most common protein in egg white.
• Ovotransferrin: composed of 686 amino acids, consists of 2 forms without phosphorus or sulfur.
• Ovomucoid: a glycoprotein with 9 disulphide bonds, having a stable spatial structure.
• Phosvitin: a phosphoprotein with about 10% phosphorus, containing iron and calcium.

Production of Egg White Powder

• Powdered egg whites are dehydrated and ground into a powder.
• The production process involves breaking, filtering, separating, storing, and spray drying.

Advantages of Egg White Powder

• Can be stored and transported at room temperature.
• Has a good shelf life and is time-saving.
• Can be easily reconstituted with water to make a liquid egg white.