Egg Structure & Its Uses in Bakery
Egg’s cooking properties are so varied that eggs have been called “the cement that holds the castle of cuisine together. ” Egg also provide steam for leavening or moisture for starch. Egg yolk adds moisturizing fats and helps emulsify the batter, giving the baked good a smooth and creamy texture. The egg whites acts as strengtheners. The eggs used in bakery mainly comes from hens. A healthy hen/chicken will lay one egg a day and this will largely depend upon it’s diet and the time of the day, as sunlight affects the production of eggs.
The size of the egg also depends on the chickens age; older the hen larger the egg An egg is a rich source of proteins as it has two types of proteins; egg white contains ‘albumen’ and the yolk contains ‘lecithin’. Structure of an Egg A whole egg contains a yolk and a white that are encased in a shell. THE SHELL It is the outer covering of the egg and is composed of calcium carbonate. It may be white or brown depending upon the breed of the chicken. The colour of the shell does not affect cooking quality, character or nutrition. EGG YOLK
It is the yolk or yellow portion which is responsible for the egg’s emulsifying properties from the fat and lecithin contained in them. Both contribute to the fine texture of baked goods and which bring the water and fat phases together in a recipe for a creamier, smoother texture. This is important when baking and making creamy sauces. The yolk also contains a little less than half of the protein. Colour of yolk varies with feed of the hen, but does not indicate the nutritional content. With the exception or riboflavin and niacin, the yolk contains a higher proportion of the eggs vitamins than the white.
The yolk of a large egg contains about 59calories. The downside is it contains 213mg of cholesterol. The yolk is held together, as there is a clean seal present, which is called as VITELLINE. Egg Yolk’s Structure: * 1/2 water | * 1/6 protein | * 1/3 fat | * emulsifiers (lecithin) | * All of the egg’s vitamins A, D and E are in the yolk. Egg yolks are one of the few foods naturally containing vitamin D. The yolk also contains more phosphorus, manganese, iron, iodine, copper, and calcium than the white, and it contains all of the zinc. EGG WHITES These are also known as Albumen. It accounts for most of an egg’s liquid weight, about 67%. Albumen is more opalescent than truly white. The cloudy appearance comes from carbon dioxide. As the egg ages, carbon dioxide escapes, so the albumen of older eggs is more transparent than that of fresher eggs. CHALAZE are twisted cordlike strands of the egg white, that anchor thet yolk in the centre of the egg. Prominent chalaze indicates higher quality. There are two types of albumen: * Thin Albumen – It is nearest to the shell.
When the egg is broke there will be a clear demarcation of the thin and the thick albumen. As the egg get older the two albumens tend to mix up into one-another. * Thick Albumen – It stands high (closer to the yolk) and spreads less than thin white in a high quality egg. It is an excellent source of riboflavin and protein. Egg White Structure: * 7/8 water | * 1/8 protein | * 0 fat | * niacin, riboflavin, chlorine, magnesium, potassium, sodium and sulphur. SHELL MEMBRANETwo shell membranes, inner and outer membrane, surrounds the albumen, they form a protective barrier against bacteria.
Air Cells forms between the membranes. | Uses of Eggs in Bakery Eggs have many uses in baking and cooking. They can bind ingredient, they can also leaven such baked high rises as souffles and sponge cakes. Their thickening talent is seen in custards and sauces. Eggs emulsify. They clarify soups and coffee. Eggs retard crystallization. They also enable coating. In general, eggs add color and flavor. COAGULATION When eggs are heated, the protein in the white and yolks starts to coagulate. This means that the liquid egg becomes firmer.
As heating continues the egg eventually becomes solid. A sauce or custard can be thickened by egg and heating, critical to many recipes. When eggs are heated, their proteins unwind (called denaturing) and break apart from their tightly bound bundles, bump up against one another, and adhere to form loose, flat and long strands. These strands are linked together in a three-dimensional mesh. Example: With egg whites because they turn from clear to opaque, forming a solid gel. Liquid gets trapped in these strands, and this causes the mixture to thicken. BINDERS
Whole raw egg adds moisture to a mixture and holds the ingredients together. As the food is heated, egg protein coagulates, thus binding ingredients together. This is a very useful property for binding in products such as meat loaves, formed meat and poultry products and for natural thickening of custards and pie fillings. The temperature of coagulation can be controlled by adjusting pH, adding salts and other ingredients. LEAVENING Eggs serve as leaveners in their ability to foam. The effectiveness of the leavening depends on the amount of air trapped within the egg.
Egg white holds much more air between its molecules as compared to the yolks. Whisking egg white incorporates air and produces foam – a relatively stable mass of bubbles. Whole eggs incorporate air less well, especially when beaten into a batter, but give a sponge cake a light texture. If left to stand, egg white will gradually collapse, but when heated or a little acid the foam of cream ot tatar or a squeeze of lemon juice helps stabilize the foam. Eg: The Angel Food Cake (Foam Cake), a white cake, tall and light in texture, is leavened only by beaten egg whites. EMULISIFICATION
Egg yolk contains lecithin which acts as an emulsifier because its proteins can wrap itself around tiny globules of oil. Adding yolk to a mixture of oil and water prevents the two liquids from separating, the emulsifier in the yolks are liasions between the two liquids and serve to stabilize the mixture. Eg: Mayonnaise, Hollandaise, etc… GLAZES Egg whites, egg yolks, whole eggs, and egg washes brushed on breads and other baked products add a rich, shiny glaze. The glaze is caused primarily by the protein and fat interaction. CLARIFIERS Eggs and egg whites have been used as a clarifier.
The process is as it sounds, the clearing of a liquid. Master chefs use it to clarify stock to produce clear consommes. ADD COLOUR AND FLAVOUR The yellow colour of egg yolk derives from the fat-soluble arytenoids in the lipid portion of lipoproteins. This rich colour means quality and the anticipation of good flavour in such recipes as pasta, mayonnaise and cakes. Over a hundred volatile components contribute to the flavour of eggs. Egg flavour provides a rich, rounded, neutral background against which other flavours can be highlighted. Conclusion