Hard-boiled eggs should be kept in the refrigerator and eaten within 4 days.

If you leave hard boiled eggs in the fridge any longer than this, the salmonella risk starts to rise very quickly.

The reason hard boiled eggs don’t last as long as raw eggs is that in cooking the eggs, a natural protective chemical layer (produced by the mother hen) is washed off the porous eggshell, allowing germs to enter.

So eat boiled eggs fairly soon after boiling them and you will have no problems. Do remember that well boiled eggs (6 minutes or more) have practically no risk of Salmonella while lightly boiled eggs may still have a small risk.

One the subject of eggs, here is the definitive guide to…

Boiling an Egg

Fill a saucepan with enough cold water to cover your egg. If the egg floats then it is too old and should be thrown away. Remove the egg, and turn on the heat, bringing the water to a strong rolling boil. If you put the lid on the pan it will boil more quickly, saving you time and money.

Take the lid off and reduce the heat to a simmer.Place your eggs in the water and let them simmer for… Well it depends on the size of the egg and how hard or runny you like them

4 minutes is usually the minimum for a small soft boiled egg and a large hard boiled egg can take about 12 minutes. Somewhere in between is your perfect egg.

If you want a hard boiled egg but intend to eat it later on in the day, you should cool it rapidly under a tap. If a hard boiled egg cools slowly it sometimes gets a totally harmless but unappealing green colour around the yolk.

How to tell a hard boiled from a fresh egg.

If you have both hard boiled and fresh eggs in the fridge you may get confused over which is which. The ‘spin test’ will sort your eggs for you. Simply place the egg on a counter and spin it fairly strongly and after it has pin 4 or 5 times lightly stop it with your finger and then remove the finger quickly. A boiled egg will just sit there, while a fresh egg will start slowly spinning again. This is because the liquid in the egg has some residual motion.

When people ask ‘how long to hard boiled eggs last’ I am assuming they are asking about hens eggs. The answer is slightly different for other fowl. Smaller eggs have a slightly shorter shelf life and larger eggs, with their thicker shells have a slightly longer life. However, to be certain, assume four days is the absolute maximum for any egg.

If you turn it into egg mayonnaise, it really should be eaten within 48 hours.

More difficult cookery questions answered…