Eggs can be stored for 30 days at room temperature, 15 days at high temperature in summer and 45 days in refrigerator. Eggs that have been stored for more than the above time are expired. The surface of this kind of egg may look normal, but the inside of the egg has long been polluted by bacteria or other microorganisms, which leads to the phenomenon that the yolk becomes scattered and loses nutrition, so it can not be eaten any more.

Matters needing attention in egg purchase

1, eggs are soaked in water. After buying back the eggs, you can put them in cold water. If the egg does not float, it means it is fresh; But if the egg floats, it means it is old.

2. Smell the eggs. You can pick it up and smell it when you buy eggs. Fresh good eggs will have a slight taste of quicklime, while old eggs will not have a taste.

3. Listen to the sound of eggs. Pick up the egg and gently shake it in your ear. If the egg has no sound, it means that the egg is fresh; But if there seems to be a sound of water shaking, it means that this is an old egg.