What is the History of the Egg?
"Eggs existed long before chickens," according to On Food and Cooking: The Science and Lore of the Kitchen by Harold McGee. "The first eggs were released, fertilized, and hatched in the ocean around 250 million years ago.  The earliest, fully land-dwelling animals, called reptiles, developed a self-contained egg with a tough, leathery skin that prevented fatal water loss. The eggs of birds, animals that arose some 100 million years later, are a refined version of this reproductive adaptation to life on land.  Thus, eggs are millions of years older than birds.  Gallus domesticus, the chicken more or less as we know it, is only a scant 4 or 5 thousand years old."

How Often Does a Hen Lay an Egg?
The entire time from ovulation to laying is about 25 hours.  Then about 30 minutes later, the hen will begin to make another one.  Hens need at least 12 hours of sunlight or artificial light to stimulate egg  laying.

What Safe Handling Instructions are on Egg Cartons?
All packages of raw, shell eggs not treated to destroy Salmonella must carry the following safe handling statement:

SAFE HANDLING INSTRUCTIONS:  To prevent illness from bacteria - keep eggs refrigerated, cook eggs until yolks are firm, and cook foods containing eggs thoroughly.

Who is "At Risk" for Eating Raw or Undercooked Eggs?
Infants, young children, older adults, pregnant women, and people with weakened immune systems are particularly vulnerable to SE infections. A chronic illness weakens the immune system, making the person vulnerable to food borne illnesses.

No one should eat foods containing raw eggs.  This includes "health food" milk shakes made with raw eggs, caesar salad, hollandaise sauce, and any other foods like homemade mayonnaise, ice cream, or eggnog made from recipes in which the egg ingredients are not cooked. However, in-shell pasteurized eggs may be used safely without cooking.

What is Candling?
Candling is the process of using light to help determine the quality of an egg.  Hand candling—holding a shell egg directly in front of a light source—is done to spot check and determine accuracy in grading.

Why Should Eggs Be Refrigerated?
Temperature fluctuation is critical to safety.  With the concern about Salmonella, eggs gathered from laying hens should be refrigerated as soon as possible.  After eggs are refrigerated, they need to stay that way.  A cold egg left out at room temperature can sweat, facilitating the growth of bacteria.  Refrigerated eggs should not be left out more than 2 hours.

Should You Wash Eggs?
No.  It's not necessary for consumers to wash eggs.  When the chicken lays the egg, a protective coating is put on the outside by the hen.

Why Do Hard-Cooked Eggs Spoil Faster than Fresh Eggs?
When shell eggs are hard cooked, the protective coating is washed away, leaving bare the pores in the shell for bacteria to enter and contaminate it.  Hard-cooked eggs should be refrigerated within 2 hours of cooking and used within a week.

How Are Eggs Handled Safely?
Proper refrigeration, cooking, and handling should prevent most egg-safety problems. Persons can enjoy eggs and dishes containing eggs if these safe handling guidelines are followed:

• Wash utensils, equipment, and work areas with hot, soapy water before and after contact with eggs.
• Don't keep eggs out of the refrigerator more than 2 hours.
• Raw eggs and other ingredients, combined according to recipe directions, should be cooked immediately or refrigerated and cooked within 24 hours.
• Serve cooked eggs and dishes containing eggs immediately after cooking, or place in shallow containers for quick cooling and refrigerate at once for later use. Use within 3 to 4 days.

Are Easter Eggs Safe?
Sometimes eggs are decorated, used as decorations, and hunted at Easter.  Here are some safety tips for Easter eggs.

• Dyeing eggs:  After hard cooking eggs, dye them and return them to the refrigerator within 2 hours.  If eggs are to be eaten, use a food-safe coloring. As with all foods, persons dyeing the eggs should wash their hands before handling the eggs.
• Decorations:  One Easter bread recipe is decorated with dyed, cooked eggs in the braided bread.  After baking, serve within 2 hours or refrigerate and use within 3 to 4 days.
• Blowing out eggshells: Because some raw eggs may contain Salmonella, you must use caution when blowing out the contents to hollow out the shell for decorating, such as for Ukrainian Easter eggs.  Use only eggs that have been kept refrigerated and are un-cracked.  To destroy bacteria that may be present on the surface of the egg, wash the egg in hot water and then rinse in a solution of 1 teaspoon liquid chlorine bleach per half cup of water. After blowing out the egg, refrigerate the contents and use within 2 to 4 days.
• Hunting Eggs:  Hard-cooked eggs for an egg hunt must be prepared with care to prevent cracking the shells.  If the shells crack, bacteria could contaminate the inside.  Eggs should be hidden in places that are protected from dirt, pets, and other sources of bacteria.  The total time for hiding and hunting eggs should not exceed 2 hours. The "found" eggs must be re-refrigerated and eaten within 7 days of cooking.

Does the Color of the Shell Affect the Egg's Nutrients?
No.  The breed of the hen determines the color of her eggs.

Araucuna chickens in South America lay eggs that range in color from medium blue to medium green.  Nutrition claims that araucuna eggs contain less cholesterol than other eggs haven't been proven.

Are Fertilized Eggs More Nutritious?
No.  There is no benefit in eating fertilized eggs.  There is no nutritional difference in fertilized eggs and infertile eggs.  Most eggs sold today are infertile; roosters are not housed with the laying hens.  If the eggs are fertile and cell development is detected during the candling process, they are removed.

Per Capita Consumption
Egg consumption in America was on a 40-year downward slide until the 1990's.  Then eggs became increasingly popular.  The following figures are from USDA's Economic Research Service.

Is the Appearance of Eggs Related to Food Safety?
Sometimes, but not usually.  Variation in egg color is due to many factors.

• Blood spots are caused by a rupture of one or more small blood vessels in the yolk at the time of ovulation.  It does not indicate the egg is unsafe.
• A cloudy white (albumen) is a sign the egg is very fresh.  A clear egg white is an indication the egg is aging.
• Pink or iridescent egg white (albumen) indicates spoilage due to Pseudomonas bacteria. Some of these microorganisms—which produce a greenish, fluorescent, water-soluble pigment—are harmful to humans.
• The color of yolk varies in shades of yellow depending upon the diet of the hen.  If she eats plenty of yellow-orange plant pigments, such as from marigold petals and yellow corn, the yolk will be a darker yellow than if she eats a colorless diet such as white cornmeal.  Artificial color additives are not permitted in eggs.
• A green ring on a hard-cooked yolk is a result of overcooking, and is caused by sulfur and iron compounds in the egg reacting on the yolk's surface.  The green color can also be caused by a high amount of iron in the cooking water.  Scrambled eggs cooked at too high a temperature or held on a steam table too long can also develop a greenish cast.  The green color is safe to consume.

How Do Time and Refrigeration Affect Egg Quality?
The egg, as laid at 105 °F, normally has no air cell.  As the egg cools, an air cell forms usually in the large end of the egg and develops between the two shell membranes.  The air cell is formed as a result of the different rates of contraction between the shell and its contents.

Over time, the white and yolk of an egg lose quality.  The yolk absorbs water from the white.  Moisture and carbon dioxide in the white evaporate through the pores, allowing more air to penetrate the shell, and the air cell becomes larger.  If broken open, the egg's contents would cover a wider area.  The white would be thinner, losing some of its thickening and leavening powers.  The yolk would be flatter, larger and more easily broken.  The chalazae (kah-LAY-zuh), the twisted cord-like strands of egg white that anchor the yolk in the center of the white, would be less prominent and weaker, allowing the yolk to move off center. Refrigeration slows the loss of quality over time.

What Does It Mean When an Egg Floats in Water?
An egg can float in water when its air cell has enlarged sufficiently to keep it buoyant.  This means the egg is old, but it may be perfectly safe to use.  Crack the egg into a bowl and examine it for an off-odor or unusual appearance before deciding to use or discard it.  A spoiled egg will have an unpleasant odor when you break open the shell, either when raw or cooked.

Safe Cooking Methods
Many cooking methods can be used to cook eggs safely including poaching, hard cooking, scrambling, frying and baking.   However, eggs must be cooked thoroughly until yolks are firm. Scrambled eggs should not be runny.  Casseroles and other dishes containing eggs should be cooked to a safe minimum internal temperature of 160 °F.  Use a food thermometer to be sure.

Use Safe Egg Recipes
Egg mixtures are safe if they reach 160 °F, so homemade ice cream and eggnog can be made safely from a cooked egg-milk mixture.  Heat it gently and use a food thermometer.

• Dry meringue shells are safe. So are divinity candy and 7-minute frosting, made by combining hot sugar syrup with beaten egg whites.  Avoid icing recipes using uncooked eggs or egg whites.
• Meringue-topped pies should be safe if baked at 350 °F for about 15 minutes.  Chiffon pies and fruit whips made with raw, beaten egg whites cannot be guaranteed to be safe.  Instead, substitute pasteurized dried egg whites, whipped cream, or a whipped topping.
• To make a recipe safe that specifies using eggs that aren't cooked, heat the eggs in a liquid from the recipe over low heat, stirring constantly, until the mixture reaches 160 °F.  Then combine it with the other ingredients and complete the recipe.
• To determine doneness in egg dishes such as quiche and casseroles, the center of the mixture should reach 160 °F when measured with a food thermometer.
• Use pasteurized eggs or egg products when preparing recipes that call for using eggs raw or undercooked.