Overview Egg Industry Parts of the egg Review of parts Grades of eggs Sizes of eggs Review
Egg Industry In 2003 the United States produced 73.93 billion table eggs. 2003 per capita consumption was 254.1 eggs. High point in per capita egg consumption was 402 eggs in 1945. Top egg producing state is Iowa with 44,271 layer hens. California is ranked # 5 with 20,073 layer hens.
Shell Eggs outer covering 9-12% of total weight The shell is the eggs first defense against bacterial contamination Made of mostly calcium carbonate Shell strength is determined by a hens diet (particularly calcium) and thickness by a hens age. Shell
Each egg has up to 17,000 pores on the shell surface. A greater number are on the larger end. Pores allow moisture and CO2 to move out and air to move in to form the air cell. A protective covering called the cuticle or the bloom covers the shell to block the pores to keep egg fresh and prevent contamination. Shell
Shell Membrane Inner and outer shell membrane. Protect against bacterial penetration Air cell forms between the two membranes. Inner shell membrane Outer shell membrane
Albumen Also known as egg white. Contains more than half the eggs total protein, potassium and sodium. More opalescent that white. Cloudy appearance comes from CO2 which escapes as the egg ages, so older eggs are clearer than fresh eggs. Tends to thin out with age. Albumen
Air Cell Empty space between the albumen and the shell. At the large end of the egg. When egg is first laid it is warm, as it cools, the content contracts and the inner shell membrane separates from the outer shell membrane forming the air cell. Air cell becomes larger with age Size of air cell is used in determining grade of egg. Air Cell
Germinal Disc The entrance leading into the center of the yolk. Slight depression on the yolk If the egg were to be fertilized-the sperm would enter through the germinal disc. Where the females genetic material is found. Germinal disc
Chalaza Ropey strands of egg white which anchor the yolk in place in the center of the egg white. The more prominent the chalaza, the fresher the egg. Does not need to be removed. Chalaza
Vitelline Membrane Also known as the yolk membrane. Clear seal which holds egg yolk. Protects the yolk from breaking. Is weakest at the germinal disc and weakens with age. Vitelline Membrane
Yolk Yellow portion of egg. 33% of the liquid weight of the egg. Contains all of the fat in the egg and a little less than half of the protein. Contains more vitamins than the egg white. The yolk is a source of food for the embryo. Yolk
Review of the Parts of an Egg Yolk Vitelline Membrane Chalaza Germinal Disc Air Cell Albumen Shell Inner shell membrane Outer Shell Membrane
Grading of Eggs Grade is determined by interior and exterior egg quality. Grade is designated by letters : AA, A, B. AA is the best grade. There is no nutritional difference between the grades. Most B grades are used by institutional egg users and never make their way to the grocery store.
Exterior The shell is checked for cleanliness, strength, texture and shape. Higher grades must be clean. Cracks or unsound shells are restricted eggs. Shell should be oval with one end larger than the other. Thin spots or rough areas may be permitted under B grade of egg.
Interior Candling method or the breakout method is used. Albumen judged based on clarity and firmness. Should be clear of discolorations or foreign bodies. Twirling an egg before a candling light will show the thickness of the albumen by observing how fast the yolk moves. The yolk is graded on distinctness of outline and absence of defects such as a blood spot. Higher grade eggs have a shallow air cell. AA <1/8 inch air cell A >3/16 inch air cell B No limit on size of air cell
Sizing of Eggs Egg size is determined by weight. Each carton contains eggs of similar weights. Grade quality and weight are not related. 6 sizes of eggs: Pee WeeSmallMediumLargeExtra Large Jumbo Less than 42 g At least 42 g At least 49g At least 56 g At least 63 g 70 g or more Weight Size
Review Questions Q: What determines the grade of an egg? A: Interior and exterior quality Q: What are the grades of eggs? A: AA, A, B Q: What determines the size of an egg? A: weight in grams Q: What are the methods for determining the interior quality for grading? A: the candling or breakout method. Q: What is the top egg producing state in the United States? A: Iowa Q: What is the per capita consumption of eggs in the US? A. 254.1 eggs per person