By Michele Bloomquist
Oct. 23, 2000 -- In recent years, the reputation of eggs has gone from fluffy goodness to hardboiled menace, thanks to their link to salmonella infection. Today, many restaurants refuse to serve eggs sunny-side up, cookbooks eliminate raw eggs from recipes for Caesar salad, and supermarkets stock cholesterol-free, pasteurized egg products.
Breakfasters everywhere are confused and afraid. Are eggs bad for me? Will they make me sick? Should I stop eating them? Is anything safe anymore?
Relax. Before you scratch eggs off your shopping list for good, let's look at the facts.
The Salmonella scare emerged in 1985 when Centers for Disease Control and Prevention (CDC) researchers first found the bacteria Salmonella enteritidis not just on the outer shells of eggs, but also inside them. The odds of buying such eggs are extremely low, according to the Food and Drug Administration (FDA) -- one in 20,000. The problem is, there's no way to tell which ones are infected. To be safe, in July the FDA recommended that eggs be kept refrigerated and used within 30 days of purchase.
What Can Go Wrong?
Salmonella infection can range from mild to severe, but its symptoms are usually clear: abdominal cramps, diarrhea, nausea, vomiting, chills, fever, or headache. These typically appear anywhere from six to 72 hours after you eat a salmonella-tainted meal, leaving you to wonder, was it the chicken? The burger? The eggs in the no-bake cheesecake?
In fact, it could be any of them, or it could have been from salmonella lurking on your kitchen sponge. That's because salmonella is everywhere -- not just in eggs. Chances are that if you tested, you'd find the pesky bacteria on your fingertips right now. Not a problem if you have a normal immune system, which can fight off the infection in a day or two. But it can lead to serious complications for the very young, the pregnant, the elderly, the ill, and those with weakened immune function.
Unlike most other high-protein foods such as chicken and beef, eggs have protection from invasion by these ever-present bacteria, thanks to their natural packaging. An egg is composed of the shell (which is lined by two membranes), the white (which has antibacterial properties), a tough yolk membrane, and finally the yolk itself. So why all the fuss? Because the bacteria may already be inside.
Inside the Egg
Until 1985, researchers thought bacteria lurking on the shell surface was the most likely source of salmonella contamination in eggs. Today, this risk is minimized because eggshells are washed and sterilized during processing. But researchers were surprised in the mid-'80s by a new finding -- salmonella lurking in the yolk membrane itself. These bacteria are literally born in the egg, entering from the infected ovaries of the laying hen, says Bessie Berry, manager of the United States Department of Agriculture's (USDA) Meat and Poultry Hotline. An added problem for the farmer is that the laying hen does not appear sick in any way.
The birds can become infected with salmonella in two ways: Either they're born from an infected mother hen, or they pick up salmonella along the way, perhaps when an unlucky fly lands on the hen's food tray and is gobbled up. Farm eggs and free-range eggs are not immune from contamination either, says Berry.
Testing the laying hens is the only way to determine infection. But testing is a staggering task when you take into account the numbers: There is one laying hen for every man, woman, and child in the United States -- about 260 million birds, according to FDA statistics. Finding the one infected egg in 20,000 is like looking for a needle in a haystack. Nevertheless, the FDA will require testing of commercial flocks -- the ones who lay the eggs for market -- by 2001.
"People think it won't happen to them, but it can," Berry says. Better to assume bacterial organisms are there and act accordingly.
Steps to Protect
Even if salmonella bacteria are within the egg, they still have to gain access to the nutrient-rich yolk to multiply -- a process hindered when the egg is fresh and the yolk membrane is intact. At that stage, the number of bacteria is very small. Refrigeration provides additional protection by limiting bacterial growth and preventing the breakdown of the membrane. So your best bet is to buy fresh eggs -- check the sell-by date on the carton, if there is one -- and keep them in the fridge. Also, make sure to use them within four weeks of purchase.
Eggs that are cracked into a bowl, beaten together, and allowed to sit also present a risk. "If the bacteria are there, they will multiply to high levels very quickly at room temperature," says Berry. For this reason, she recommends cooking eggs within two hours of cracking them.
But bacteria already in the egg don't cause all cases of salmonella infection. Contamination can also occur in your kitchen. Salmonella-free eggs may not stay that way if you whisk them with a fork that was also used to handle contaminated raw poultry, for example. "Remember to wash everything, including your hands, that has come into contact with raw food before handling something that won't be cooked," Berry says.
Cook Them Well or Use Pasteurized Eggs
In the rare chance that you do buy an egg contaminated with salmonella bacteria, there's some reassuring news: Cooking kills the bacteria. There is no way for you to know at home if the egg is contaminated -- the egg won't look, smell, or taste different from any other egg, says Marjorie Davidson, a food safety education expert at the FDA. Because of this, she recommends cooking all eggs thoroughly: Salmonella bacteria are killed at temperatures above 160 degrees Fahrenheit. Both the FDA and USDA recommend cooking raw (unpasteurized) eggs until the yolks and whites are completely firm.
And don't forget about dishes containing eggs, like stuffing and meatloaf. They also need to be cooked thoroughly, says Davidson. She suggests buying a cooking thermometer. Check all dishes containing eggs to make sure the temperature is 160 degrees or higher in the center when finished cooking.
Pasteurized eggs are available in test markets around the country for those who want to make, for example, a protein shake containing an uncooked egg or sunny-side-up eggs with a runny yolk. These eggs have been heated to 145 degrees Fahrenheit for three and a half minutes. Egg products in containers, such as Egg Beaters (essentially egg whites that have been colored), are also pasteurized.
"Pasteurized eggs are available in some areas, but not everywhere," says Davidson. "If you can't find pasteurized eggs, many chefs and cookbooks have done an excellent job of converting raw recipes -- like eggnog -- to cooked ones."
If a recipe calls for a room-temperature egg, half an hour on the counter should do the trick, says Berry. Don't leave eggs out longer than that. Also, casseroles and recipes that contain eggs should be kept refrigerated after preparation if you aren't cooking them right away. Even then, don't store them in the fridge for longer than two hours before cooking, she says.
In short, with the proper precautions, eggs aren't so bad after all. "Like any product that you eat," Davidson says, "you can avoid illness by knowing how to buy, store, handle, and cook eggs safely."
Michele Bloomquist is a contributing editor for WebMD. She lives in Portland, Ore.
Related WebMD Information
Egg Handling Tips
Salmonella Questions and Answers
Salmonella Outbreaks Decline -- But Threat Remains
The Egg Nutrition Center
American Egg Board
FDA Center for Food Safety & Applied Nutrition
United States Department of Agriculture
©1996-2005 WebMD Inc. All rights reserved.