For: ADVS 1110 Introduction to Animal Science Eggcellent Eggs!! For: ADVS 1110 Introduction to Animal Science

Types of Eggs

Overview Egg Industry Parts of the egg Grades of eggs Sizes of eggs

Egg Industry In 2015 the United States produced 83 billion table eggs. 2015 per capita consumption was 252.9 eggs. High point in per capita egg consumption was 402 eggs in 1945. Per capita consumption reached it lowest in 1991 @ 233.9 eggs.

Egg Industry Current Top Egg Producing States: Iowa- 45,459,000 layers Ohio- 32,604,000 layers Indiana- 28,437,000 layers Pennsylvania- 25,841,000 layers Texas- 19,302,000 layers Utah ranks 31st.

The Parts of the Egg

The Parts of an Egg Albumen Shell Yolk Air Cell Outer Shell Membrane Chalaza Inner shell membrane Germinal Disc Vitelline Membrane

The Primary Components of the Egg: Shell Membranes Albumen Yolk

Shell Egg’s outer covering 9-12% of total weight The shell is the egg’s 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

Albumen Also known as “egg white.” Contains more than half the eggs total protein, potassium and sodium. More opalescent than 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.

Germinal Disc The entrance leading into 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 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 the main source of nutrients for the embryo.

The Parts of an Egg Albumen Shell Yolk Air Cell Outer Shell Membrane Chalaza Inner shell membrane Germinal Disc Vitelline 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.

Summary: Exterior Quality Factors Cleanliness of shell Soundness of shell (e.g., cracks, checks, and texture, etc.) Shape

Interior “Candling” method or the breakout method is used. (visual appraisal with light through egg) 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

Interior Candling eggs by hand.

Interior Candling a good egg.

Summary: Interior Quality Factors Albumen thickness Condition of yolk Size and condition of air cell Abnormalities (e.g., blood spots, meat spots, etc.)

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: Size Pee Wee Small Medium Large Extra Large Jumbo

Consumer Weight Classes of Eggs: Net Weight Per Dozen Size Ounces (per dozen) Jumbo 30 Extra Large 27 Large 24 Medium 21 Small 18 Peewee 15

Question: Which came first the chicken or the egg?

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