If you boil an egg for five or 10 minutes, it becomes firm and cooked. If you boil it for hours, it becomes rubbery and overcooked. Beyond that, things get a little mysterious. Eggs are full of coiled-up protein molecules.
According to The Kitchn, the first sign that your boiled eggs were left on the stove too long is if their yolks are a strange gray or white color, or seem to be falling apart. The other indicator that your eggs were over-boiled is if they smell like sulfur after you freshly peeled them.
When you boil eggs, hydrogen sulphide - a toxic gas is released in the whites of the egg. This happens especially when you overboil the eggs. If you have noticed, overcooked eggs have a green coating on their yolk, which is a signal that you should not eat them.
Perfect hard-boiled eggs have tender whites and opaque yellow yolks, but cooked too long and the middle turns green. Learn why this color change happens and why there's a strong odor that follows.
Shelly McKee, a food scientist at Deb-El Foods and an expert on egg chemistry, said that boiling an egg for a long time would cause it to expel moisture. As the proteins in the egg white clump together ever more tightly, they would squeeze out the water contained within the egg.
4 minutes for slightly set yolk and set white. 5 minutes for a medium cooked firmer yolk and white. 6 minutes for hard boiled with lightly soft yolk. 8 minutes for firmly hard boiled.
Spin the egg on a flat surface and stop it suddenly with your index finger. If it stays still, it's hard boiled. If it continues to wobble, it's raw. If the egg is dark or opaque when you shine a flashlight through it or it feels solid when you shake it, it's hard boiled.
You'll know that your egg is perfectly cooked if it has an opaque, yellow center. The yolk of an overcooked egg, on the other hand, will turn a greenish-gray color.
The rapid cooling of the eggs contracts the egg whites, releasing them from the egg's membrane. It also firms the egg white proteins, making them easier to peel. Cool the eggs for at least 15 minutes for even easier peeling.
This is because the egg white or “albumen” in a fresh egg has a relatively low pH level, making it acidic. When cooked, these fresh egg whites bond strongly to the inner shell's membrane. As an egg ages, the pH level rises and the inner membrane is less likely to bond to the albumen, so the shell peels off much easier.
Undercooked, it will have a runny yolk that's at best off-putting, at worst unsafe. Overcooked, a hard-boiled egg is tough and rubbery and borderline inedible.
Consuming an undercooked egg can make you sick.
The inside of eggs do sometimes carry salmonella. If that germ is there, it doesn't go away in a raw egg or even necessarily in a lightly cooked one, the CDC reports, which is why it's so important to cook your eggs properly.
These germs can spread from the birds to their eggs. If you eat raw or undercooked eggs, you can get sick. Always handle and cook eggs properly to prevent illness.
For one to four eggs, bring the water to a rolling boil, cover the pot, and turn the heat down to its lowest setting for 12-14 minutes. For five to eight eggs, cook for 15 to 18 minutes. For nine to one dozen eggs, cook for 20 minutes. After cooking, transfer the eggs to a bowl of ice water.
Fill pot with water to completely cover the eggs at least 1 inch above eggs and turn heat to high. Bring water to a boil, takes approximately 15 minutes. As soon as eggs start to boil, let boil for 10-12 minutes (I do 11 minutes).
As soon as the water comes to a boil, turn off the heat! The eggs sit for about 15 minutes to let them cook fully through.
Hard-boiled eggs can be kept for 1 week in your refrigerator. If the egg develops an unmistakable odor or slimy or chalky texture, discard it, as eating spoiled eggs can make you sick.
Salmonella infection is usually caused by eating raw or undercooked meat, poultry, and eggs or egg products or by drinking unpasteurized milk. The incubation period — the time between exposure and illness — can be 6 hours to 6 days. Often, people who have salmonella infection think they have the stomach flu.
Add salt and vinegar to the water before cooking.
The salt permeates the shell a little bit, and the vinegar helps to break down the shells, making them easier to peel.
At the lower pH of a fresh egg, the proteins in the egg white bind tightly to the keratin in the membrane during the cooking process, which makes it nearly impossible to remove the shell without chunks of white attached.
You can't tell if an egg has salmonella just by looking at it. The bacteria can be present inside an egg as well as on the shell. Cooking food thoroughly can kill salmonella. Be aware that runny, poached, or soft eggs aren't fully cooked — even if they are delicious.
The eggs stored in cold temperature tend to undergo condensation when they are taken out to room temperature. This promotes the growth of bacteria over the egg shell, thereby contaminating the egg and making it harmful for human consumption.