Eggs (usually hen eggs) are one of the most important raw materials used in baking. Eggs are composed of three main parts shell, the white or albumen and the yolk. The latter two are of great importance in bakery. Albumen accounts for almost 70 per cent of an egg's liquid weight. When egg albumen is beaten vigorously, it foams and increases in volume by 6 to 8 times. Egg foams give volume to cake-batters and are essential for making angel and sponge cakes. On heating, the egg protein network coagulates and contributes rigidity to hold the structure. It is the yolk or yellow portion which is responsible for the egg's emulsifying properties from the fat and lecithin containedin them (whites do not contain fat). Both contribute to the fine texture of baked products and bring the water and fat phases together in a recipe for a creamier, smoother texture. This is important in baking. Eggs used in excess amount will give abnormal volume to the cake. Crust will be dark, thick and peeled off as a flake. Texture will be dry and rough due to evaporation of moisture. Proteins of eggs are of particular importance. Coagulation of protein during baking contributes to the structure of finished product and reduces tenderness.
Besides protein, it also contains fats, minerals and vitamins that are essential for providing energy and maintenance. Fresh eggs have strong intact albumen which forms good leavening when whipped.But on aging, the egg white becomes thin. For best results, the eggs should be brought to room temperature before use. Egg shells may be infested by salmonella (a bacterium that can cause food poisoning), which will spread on contact while handling the egg.Hence hygienic handling is necessary.
Functions of eggs are
- Egg whites act as strengtheners contributing structure to the baked products,
- Incorporates air when beaten, add colour and flavour,
- Provide protein, fat and liquid
- Brings about emulsification of fats in the batter, giving the baked products a smooth and creamy texture
- Provide moisture for starch gelatinization and steam for leavening
- Develop characteristic texture, mouth feel and taste.
Replacing eggs alters the product quality and may call for addition of additives. There aresubstitutesfor fresh eggs, but they do alter the recipe.Because of their important properties eggs are used as moistening, enriching, coloring and aerating agents, and enriching qualities add to the food value of baked foods. Fresh whole eggs are the best form of eggs for use in the bakery. Eggs are perishable due to the putrefying bacteria that enter through the porous shell. Frozen and dried eggs are also used in different parts of the world.
It is used in baking industry because of it has characteristic property of good stable foam formation that can support large quantities of flour or sugar. These foams are capable of holding other ingredients until heat coagulation can occur in the oven to develop stable protein matrix. Egg Globulins are primarily responsible for lowering surface tension and increase viscosity where air gets incorporated. As foam develops bubbles become smaller, surface is greatly enlarged and ovomucin (protein) undergoes surface denaturation to form a solid film, which contributes to the stability of the unheated foam and volume of foam increases. Ovalbumin, which is readily heat coagulable, set up in heat and supports many times its weight of sugar and flour. Albumin having pH 6.5-9.5 has greatest foaming power. The pH of egg white is 7.6.
Yolk is not commonly employed as a foaming agent with the exception of a yellow sponge type baked product. Egg yolk has a foaming ability that is different from egg white which is oil-water-air emulsion complex.
Points to be considered while using egg as ingredient:
- Weight of sugar should exceed the weight of flour.
- Weight of total liquid should equal or slightly exceed the weight of sugar.
- In pound or layer cake, the weight of egg solids should approximate 1/4th of the weight of shortening.
Storage of eggs:
- Always store eggs in their carton
- Eggs should never be washed the microscopic pores get blocked besides aiding salmonella bacteria to penetrate in to the interior of egg.
- Place the eggs round side up to keep the egg yolk centered in the white and away from the air pocket.
Egg safety practices:
- Select intact eggs of good grade.
- Hands, utensils and surfaces should be washed thoroughly while and after handling eggs.
- Cook to appropriate temperatures.
- Eggs should be stored and refrigerated properly to prevent cross contamination.
- Cracked eggs and those having large bloodspots and unusual odors should be discarded