1, cooked salted duck eggs are not particularly salty. If the egg skin is not broken after cooking, it can be stored in the refrigerator for one month. If it is salty, it can be stored in the refrigerator for more than 3 months without breaking the skin. If the skin is broken for four or five days, you must eat it as soon as possible, and it will deteriorate after a long time. Cooked salted duck eggs with broken skin should be placed in a closed container or sealed with plastic wrap at the mouth of the container and put into the refrigerator to prevent odor and bacteria from breeding.

2. Appearance method. Duck eggs are covered with frost powder, which is not smooth when rubbed by hand. Fresh eggs are intact, while stale duck eggs are smooth, black, incomplete and cracked.

3. technique. When buying duck eggs, hold them with your thumb, forefinger and middle finger and shake them. Fresh eggs are silent, and bad people will send out Tik Tok when shaking hands. The louder the voice, the worse.

4. Irradiation method. Hold the duck egg gently with your hand and observe the light. Good duck egg protein is clear and transparent, with a small empty room at one end, while bad duck egg protein is dark and has a large empty room. Some duck eggs are stained, which is a sign of obsolescence or deterioration.