A: The green ring around the yolk of a hard cooked egg happens because hydrogen in the egg white combines with sulfur in the yolk. The cause is most often related to boiling the eggs too hard for too long. The green ring can also be caused by a high amount of iron in the cooking water.
If you see any of these colors, discard the egg immediately. Off-color egg white, green or iridescent – Spoilage due to Pseudomonas bacteria, a very common type of bacteria that healthy people often carry without knowing it.
Egg white that isn't white – If the egg white isn't clear or cloudy white, it may be bad. If your egg white has a green or iridescent look, it may have harmful bacteria. It may not be safe for consumption. If you notice that the color is off, smell your egg.
They should discard eggs with any unusual discoloration inside, such as a pink, iridescent, or greenish egg white or yolk. However, eggs that develop a green ring on the hard-cooked yolk after cooking are safe to eat, according to the USDA.
If the egg white is pink or iridescent this is an indication of spoilage due to Pseudomonas bacteria. Some of these bacteria can make us sick when eaten and they will produce a greenish, fluorescent, water-soluble color. Also, a spoiled egg (cooked or raw) will have an unpleasant odor once you crack it open.
The green ring is harmless and safe to eat. To avoid green eggs, hard-cook instead of hard-boiling eggs: Place eggs in a single layer in saucepan. Add cold tap water and cover by at least 1 inch above the eggs.
You can eat eggs past their expiration date. Just be sure to keep your eggs egg-cellent by storing them correctly. If you don't know if an egg is good or not, you can try the float test or give it a whiff. If it doesn't pass the test, throw it away.
If the eggs sink to the bottom and lay flat on their side, they're still fresh. However, if they sink, but stand on one end at the bottom of the glass or bowl, they're not as fresh but still edible. Of course, if any eggs float to the top, they shouldn't be eaten.
A greenish-gray ring may appear around a hard-cooked egg yolk. It's unattractive, but not harmful. The ring is caused by a chemical reaction involving sulfur (from the egg white) and iron (from the egg yolk), which naturally react to form ferrous sulfide at the surface of the yolk.
What's a green egg? The result of crossbreeding genes from blue eggshells with genes from brown eggshells. These festive-colored eggs are green on the outside and blue on the inside. Only a few chicken breeds can produce this colored eggshell, which makes them a rarer find.
The shade of an egg yolk is completely determined by the hen's diet. Hens that are given feed full of yellow-orange pigments will lay eggs with darker yolks. It's as simple as that! No artificial coloring is allowed in chicken feed, but some farmers will add marigold petals to give yolks an orangey color boost.
Those funky, discolored rings in your hard-boiled eggs may make you wonder if they are harmful to eat. Fortunately, the United States Department of Agriculture (USDA) website clearly states the green or gray color in the eggs is “safe to consume.” So, if you happen to see a little ring around your egg, don't worry!
The green ring is harmless and occurs when eggs have been cooked for too long or at too high a temperature. The American Egg Board suggests that you cook eggs in hot, not boiling, water, and then cool immediately to minimize the green ring.
Hard-boiled eggs, peeled or unpeeled, are safe to eat up to seven days or one full week after they were cooked. To make sure they stay fresh, allow the cooked eggs cool a bit, and then store them in a sealed container in the refrigerator.
The water test for egg freshness
Very fresh eggs will sink to the bottom and lay on their sides. If an egg stays at the bottom but stands on its small end, it's still acceptable to eat; just not quite as fresh.
Eggs may be refrigerated three to five weeks from the day they are placed in the refrigerator. The "Sell-By" date will usually expire during that length of time, but the eggs will be perfectly safe to use. Always purchase eggs before the "Sell-By" or EXP (expiration) date on the carton.
The case for refrigeration, however, is bolstered by the fact that the shelf life of refrigerated eggs is around 45 days, whereas unrefrigerated eggs are good for only about 21 days.
If they sink to the bottom and lay flat on one side, they are fresh and good to eat. A bad egg will float because of the large air cell that forms at its base. Any floating eggs should be thrown out.
Old eggs should always be disposed of responsibly to avoid contamination and food-borne illnesses. You can choose to compost, feed them to animals, recycle them at local centers, or throw them in the trash. Eggs with foul odors or discoloration may be spoiled and should not be eaten.
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.
Black or green spots inside the egg may be the result of bacterial or fungal contamination of the egg. If you come across an egg with black or green spots discard the egg. Off color egg whites, such as green or iridescent colors may be from spoilage due to bacteria.
Hard-cooked eggs may be difficult to peel if they are very fresh. This is because an egg shrinks inside during storage, which pulls the inner membrane away from the inside of the shell. For this reason, a hard-cooked egg will peel more easily if it has been stored for 1 or 2 weeks before it is cooked.
Refrigerator Storage: Refrigerate eggs at 40°F or less. Store them in their original carton on an inside shelf and away from pungent foods. The temperature on an inside shelf remains more constant than one on the door, which is opened and closed frequently.