Egg Food Safety Frequently Asked Questions

EGG STRUCTURE AND COMPOSITION

Doesn't the egg shell help protect an egg from bacteria?

How often does a hen lay an egg?

How do bacteria, like Salmonella, infect eggs?

What part inside the egg carries bacteria?

What determines whether an egg is white or brown?

Is the internal appearance of eggs related to egg safety?

What is a double yolk egg? How are they formed?

Does a blood spot mean an egg is contaminated?

PURCHASING EGGS AND STORAGE

How are eggs transported safely to stores?

What points should you consider when buying eggs?

What is grading of eggs and is it mandatory?

What safe handling instructions are on egg cartons?

Are all eggs kosher?

Why should eggs be refrigerated?

Should you wash eggs after purchasing in a grocery store?

What’s the best way to store eggs?

How long are eggs safe to eat after purchase?

I just realized I left the egg carton on the kitchen counter overnight. Are the eggs safe to use?

EGG HANDLING AND PREPARATION

Is it safe to use eggs that have cracks?

What exactly is cross-contamination and what should I do about it?

Is it safe to reuse egg cartons?

What is the best temperature to cook an egg?

Why do hard-cooked eggs spoil faster than fresh eggs?

What should I do with egg-containing leftovers?

EGGS AND FOODBORNE ILLNESS

What is foodborne illness?

How does Salmonella infect eggs?

What will happen if I eat an egg containing Salmonella?

I purchased eggs from my local grocery store and I got sick after eating them. What should I do?

What usually causes salmonellosis?

Are eggs the only source of Salmonella bacteria?

What is being done about Salmonella in eggs?

Can shell eggs be pasteurized or irradiated to destroy Salmonella?

Are egg products pasteurized?

USING EGGS FOR SPECIAL OCCASIONS

How can I safely color and decorate hard-cooked eggs for Easter?

What’s the best way to safely pack eggs for camping trips, picnics, and other outdoor activities?

Once I’ve cooked an egg dish, can I leave it out for buffet serving?

EGG SAFETY MISCELLANEOUS

Do egg producers inject their hens with hormones?

Is there any chance the eggs I could buy at the grocery store could be fertilized?

EGG STRUCTURE AND COMPOSITION

Doesn't the egg shell help protect an egg from bacteria?

Yes and no. The structure and composition of an egg provides many natural barriers to prevent passage of bacteria into the egg and discourage growth inside the egg. These natural protective barriers include the shell, the shell and yolk membranes, and layers of the white. The structure of the shell and shell membranes prevent bacteria from entering the egg. Both the shell membranes and white contain lysozyme, a substance that helps prevent contamination by physically damaging the bacteria. The layers of white also discourage bacterial growth because they are alkaline, bind nutrients bacteria need, and contain nutrients in a form that bacteria cannot use. The thick white discourages the movement of bacteria towards the yolk, which contains nutrients bacteria need. The last layer of white is composed of thick ropey strands, called chalazae, which holds the yolk centered in the egg where it receives the maximum protection from bacteria by all the other layers.

How often does a hen lay an egg?

The time from ovulation to laying is about 25 hours. Then about 30 minutes later, the hen will begin to form another egg.

How do bacteria, like Salmonella, infect eggs?

Bacteria can be both on the outside and inside of a shell egg. Eggs can become infected by fecal contamination when the egg exits the hen's body or by dirt or dust in the environment; that's why eggs are washed and sanitized at the processing plant. Bacteria can also be inside an uncracked, whole egg. Contamination of eggs may be due to bacteria within the hen's ovary or oviduct being transferred into the contents before the shell forms around the yolk and white. The inside of an egg was once considered almost sterile. Over the years, however, scientists have found that Salmonella Enteritidis has the ability to grow both in the egg yolk and white.

What part inside the egg carries bacteria?

Researchers say that, if present, most bacteria is usually in the yolk. The yolk contains nutrients bacteria need to grow. Bacteria have also been found to grow in the white, however not as often as in the yolk. This is why the Egg Safety Center and FDA advise not to eat raw or undercooked egg yolks and whites or products containing raw or undercooked eggs.

What determines whether an egg is white or brown?

The breed of the chicken determines shell color of an egg—the white hens lay white eggs and the brown hens lay brown eggs. Brown chickens are usually larger and require more food to make an egg, which is why brown eggs cost more than white eggs.

Is the internal appearance of eggs related to egg safety?

The appearance of eggs may sometimes be related to food safety, but not usually. Variation in egg color is due to many factors. See the table below for some variations in egg appearance.

Appearance Cause
Blood spot/meat spot Rupture of one or more small blood vessels in the yolk at the time of ovulation or deposition of tissue during egg formation
Cloudy egg white Egg is extremely fresh
Color of yolk Depends upon the pigments found in the feed in the hens diet
Green ring on hard-cooked yolk Caused by sulfur and iron compounds in the reacting on the surface of the yolk, result of overcooking
Off-color such as pink, green or iridescent egg white Spoilage due to Pseudomonas bacteria, which produces a greenish, fluorescent, water-soluble pigment in the egg white
Black or green spots inside the egg Results of bacterial or fungal contamination of the egg

What is a double yolk egg? How are they formed?

A double yolk occurs in an egg when a chicken releases two yolks into the same shell. Double yolks are usually produced by young chickens. Their reproductive systems have not fully matured, and they periodically release two yolks instead of one. Double yolks can also come from older chickens nearing the end of their egg producing period. These eggs are perfectly safe to eat, and are said to bring good luck when you find them.

Does a blood spot mean an egg is contaminated?

No. Blood or meat spots are occasionally found on an egg yolk and are merely an error on the part of the hen. They’re caused by the rupture of a blood vessel on the yolk surface when it’s being formed or by a similar accident in the wall of the oviduct. Most eggs with blood or meat spots are detected by electronic spotters and never reach the market, but even with electronic scanners it’s impossible to catch them all. Eggs with blood spots and meat spots are fit to eat.

PURCHASING EGGS AND STORAGE

How are eggs transported safely to stores?

The U.S. Department of Commerce's 1990 Sanitary Food Transportation Act requires that vehicles be dedicated to transporting food only. On August 27, 1999, FSIS made effective a rule requiring:

  • Shell eggs packed for consumers be stored and transported under refrigeration at an ambient (surrounding) air temperature not to exceed 45° F;
  • All packed shell eggs be labeled with a statement that refrigeration is required; and
  • Any shell eggs imported into the United States, packed for consumer use, include a certification that they have been stored and transported at an ambient temperature of no greater than 45° F.

What points should you consider when buying eggs?

  • Always purchase eggs from a refrigerated case.
  • Choose eggs with clean, uncracked shells.
  • Don't buy out-of-date eggs.
  • Look for the USDA grade shield or mark. Graded eggs must meet standards for quality and size.
  • Choose the size most useful and economical for your lifestyle.
  • When purchasing egg products or substitutes, look for containers that are tightly sealed and unopened.

What is grading of eggs and is it mandatory?

Inspection, for wholesomeness, is mandatory but grading, for quality, is voluntary. If companies choose to have their eggs graded, they pay for this USDA service. The USDA grade shield on the carton means that the eggs were graded for quality and checked for weight (size) under the supervision of a trained USDA grader. Compliance with quality standards, grades, and weights is monitored by USDA. State agencies monitor compliance for egg packers who do not use the USDA grading service. These cartons will bear a term such as "Grade A" on their cartons without the USDA shield.

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.

Are all eggs kosher?

All eggs are considered kosher. Since they aren't slaughtered or mixed with other non-kosher foods (treif), they are kosher as long as they are broken open and don't have any blood spots. A blood spot makes the egg unclean, or not kosher. Eggs are also pareve, which means they can be consumed with dairy (milk) or meat.

Why should eggs be refrigerated?

Temperature fluctuation is critical to egg safety. Eggs are required by FDA to be refrigerated as soon as possible. After eggs are refrigerated, it is important to keep them that way. A cold egg left out at room temperature can sweat, facilitating the growth of bacteria that could contaminate the egg. Refrigerated eggs should not be left out more than two hours.

Should you wash eggs after purchasing in a grocery store?

No, it's not necessary to wash eggs after purchasing them in a grocery store. At the egg processing plant, government regulations require that USDA-graded eggs be carefully washed and sanitized before being packed and packaged for the store.

What’s the best way to store eggs?

The best way to store eggs is to keep them in their carton and not in the egg container that may come with the refrigerator in case you need to look at the Julian or expiration date. The carton should be placed in the coldest part of the refrigerator, not in the door, where temperatures may fluctuate when it is opened and closed.

How long are eggs safe to eat after purchase?

As long are they are kept refrigerated at 45 °F or lower, fresh shell eggs are safe to be consumed four to five weeks beyond the carton’s Julian date. Egg cartons with the USDA grademark must display a “Julian date,”* the date the eggs were packed. The Julian date is usually found on the short side of the carton and represents the consecutive days of the year with the number 001 as January 1 and December 31 as 365. Although not required, cartons may also carry an expiration date (EXP) beyond which the eggs should not be sold, but are still safe to eat. On cartons with the USDA grademark, this date cannot exceed 30 days after the eggs were packed in the carton. Depending on the retailer, the expiration date may be less than 30 days. Eggs packed in cartons without the USDA grademark are governed by the laws of their states.

I just realized I left the egg carton on the kitchen counter overnight. Are the eggs safe to use?

Maintaining a consistent, cool temperature is critical to safety. After eggs are refrigerated, it is important that they 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 two hours.

EGG HANDLING AND PREPARATION

Is it safe to use eggs that have cracks?

Bacteria can enter eggs through cracks in the shell. Never purchase cracked eggs. However, if eggs crack on the way home from the store, break them into a clean container, cover it tightly, keep refrigerated, and use within two days. When preparing, be sure to cook eggs thoroughly, with both the white and yolk firm.

What exactly is cross-contamination and what should I do about it?

Cross-contamination is the spread of bacteria from people to food or from one food or piece of equipment to another. To help prevent cross-contamination, it’s important to separate foods—especially raw meat, seafood, eggs, and poultry—from other foods as well as wash all hands, utensils and surfaces with warm, soapy water before and after handling raw eggs.

Is it safe to reuse egg cartons?

Eggs are washed and sanitized before being packed in clean, brand new egg cartons, eliminating bacteria that may have been present on the egg shell. While the cartons and eggs are clean after they are processed, there is still the potential for the eggs and carton to become contaminated via cross-contamination, either at the store, during handling, and/or storage in the refrigerator at home. The Egg Safety Center would recommend discarding egg cartons in the trash and not reusing them.

What is the best temperature to cook an egg?

Adequate cooking brings eggs to a temperature high enough to destroy bacteria that might be present in the egg yolk or egg white. Egg white coagulates between 144 and 149° F, egg yolk coagulates between 149 and 158° F and whole eggs between 144 and 158° F. If the eggs are to be used in a recipe with other food items, dilute the eggs with liquid or other ingredients, such as milk, or sugar (at least ¼ cup liquid or sugar per egg as in custard) and cook the egg mixture to 160° F to destroy harmful bacteria.

Why do hard-cooked eggs spoil faster than fresh eggs?

When shell eggs are hard cooked, the protective coating is washed away leaving the pores in the shell open for bacteria to enter. Hard-cooked eggs should be refrigerated within two hours of cooking and used within one week.

What should I do with egg-containing leftovers?

Promptly after serving, refrigerate any egg-containing leftovers. Thoroughly reheat leftovers and eat them within two to three days. Without tasting them, discard any egg-containing leftovers that have been refrigerated more than three days.

EGGS AND FOODBORNE ILLNESS

What is foodborne illness?

All foods have the ability to carry microorganisms (like bacteria and viruses) or toxins that can potentially cause illness. If microorganisms or toxins are introduced to food or if bacteria are allowed to grow in or on food, foodborne illness can result. Common symptoms of foodborne illness include headache, nausea, vomiting, diarrhea, and cramps.

How does Salmonella infect eggs?

Salmonella are found in the intestinal tracts of animals, birds, reptiles, insects and humans. Salmonella may be found on the outside of the egg shell before the egg is washed or it may be found inside the egg if the hen was infected prior to egg laying.

What will happen if I eat an egg containing Salmonella?

Symptoms of salmonellosis include abdominal cramps, diarrhea, nausea, vomiting, chills, fever and/or headache within six to 72 hours after eating the contaminated food. The symptoms usually last only a day or two in healthy people but can lead to serious complications in young children, pregnant women, the elderly, and immune-compromised individuals.

I purchased eggs from my local grocery store and I got sick after eating them. What should I do?

The basic procedure for placing a complaint with a company is to call the number located on the egg carton. If the number is not present on the carton, you could request the customer complaint or inquiry number from the store manager or go online and look up the company or distribution center phone number and request to speak with someone in sales or quality. You will give them your information and from there they will be able to handle your complaint.

What usually causes salmonellosis?

Salmonellosis outbreaks have been related to chicken, eggs, pork and cheese, cantaloupe, tomatoes, alfalfa sprouts, orange juice and cereal. Human carriers play a big role in transmitting some types of salmonellosis. Salmonella can easily spread from one food to another, too. The majority of reported salmonellosis outbreaks involving eggs or egg-containing foods has occurred in food service kitchens and were the result of inadequate refrigeration, improper handling and/or insufficient cooking.

Are eggs the only source of Salmonella bacteria?

No. Salmonella are widely found in nature and easily spread. Salmonella can be found in the intestinal tracts of animals, birds, reptiles, insects and people. While the egg itself may not be contaminated when you buy it, it can become cross-contaminated from various sources such as kitchen utensils and surfaces, hands, pets, and other foods.

What is being done about Salmonella in eggs?

The egg industry, the public health community and government agencies have been working diligently to address Salmonella Enteritidis (SE) in eggs from production all the way through to preparation. Egg safety begins with industry programs that require food safety practices on the farm. These practices include procurement of Salmonella free chicks, biosecurity, pest control, cleaning and disinfection of poultry houses, and vaccination of chicks. To hinder SE from growing in the egg in the rare event it's present, eggs are held at low temperatures following lay, transport to the processing plant, and after processing and packing. The public health community uses education programs to encourage food preparers to use safe food-handling practices. Along with state agriculture departments, the United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) have developed national standards with the goal of reducing egg-related salmonellosis. Scientists continue to conduct research to discover how SE gets into flocks and how its presence might be further reduced.

Can shell eggs be pasteurized or irradiated to destroy Salmonella?

Yes, pasteurized in-shell eggs are available in some areas in the U.S. Shell eggs have recently been approved for irradiation by the U.S. Food and Drug Administration but are not yet available commercially.

Are egg products pasteurized?

All egg products are required by law to be pasteurized. Approximately one third of all eggs produced in the U.S. today are broken and further processed to make egg products that are sold as retail or food service items or ingredients for commercial food manufacturers. These may be whole egg, egg whites, or egg yolks, and may be liquid, frozen or dried. The safety of egg products is regulated by the USDA Food Safety Inspection Service.

USING EGGS FOR SPECIAL OCCASIONS

How can I safely color and decorate hard-cooked eggs for Easter?

Before any type of interaction with eggs, it is important to first wash your hands and your working area thoroughly. Continue to do so at every step including cooking, cooling and dyeing of eggs. It is important to refrigerate hard-cooked eggs if you won’t be coloring them right after cooking and cooling. Color only uncracked eggs. If any eggs crack during dyeing or while on display, discard them along with any eggs that have been out of refrigeration for more than two hours. If hard-cooked eggs are kept out of refrigeration for many hours or several days for a decoration or for hiding, discard the eggs immediately after use. If you hide eggs, consider hiding places carefully, avoiding areas where the eggs might come into contact with dirt, pets, wild animals, birds, reptiles, insects or lawn chemicals.

What’s the best way to safely pack eggs for camping trips, picnics, and other outdoor activities?

If you tote raw eggs or hard-cooked eggs on outings, leave them in their shells. Pack them along with deviled eggs and other cold dishes in an insulated bag or cooler with ice or freezer packs. Put the cooler in the shade and open it as infrequently as you can to help keep these foods at 40° F or lower. The foods will stay refrigerator-cold as long as the ice lasts. If it is a warm egg-containing dish, use thermal containers to keep hot egg dishes hot (140° F or higher). For hiking, backpacking, camping and boating, when refrigeration facilities aren’t available, buy dried eggs from supermarkets or sporting goods stores and reconstitute them with purified water. Coating shell eggs with petroleum jelly or wax is not a suitable substitute for refrigeration

Once I’ve cooked an egg dish, can I leave it out for buffet serving?

While proper cooking destroys any bacteria that may have been present in an egg, an egg dish may be cross-contaminated after cooking by people, other foods, cooking utensils or equipment. If a dish is contaminated, bacteria will multiply rapidly at temperatures between 40 and 140°F. Promptly serve eggs and dishes containing eggs after cooking. If you are serving buffet style, use ice or freezer packs with commercial coolant to keep cold foods cold (40°F or lower) and food warmers or thermal containers to keep hot foods hot (140°F or higher). Serve buffet foods in small dishes and replenish them with fresh dishes often, rather than leaving foods at room temperature where bacteria can thrive.

EGG SAFETY MISCELLANEOUS

Do egg producers inject their hens with hormones?

No, growth hormones are never fed to egg-laying hens in the U.S. Laying hens are feed a high quality, nutritionally balanced diet made up of mostly corn, soybean meal, vitamins and minerals. The feed is carefully formulated with the proper nutrients to produce safe, quality eggs.

Is there any chance the eggs I could buy at the grocery store could be fertilized?

Hens that produce eggs commercially never encounter a rooster during their life cycle, so there is no way an egg carton you purchase at the grocery store could contain an egg with an embryo.