Why do fresh duck eggs get salty after being soaked in a strong salt solution for 12 days?

Fresh duck eggs absorb salt from the strong salt solution due to osmosis, where water moves out of the egg and salt moves in to balance the concentration on both sides of the eggshell. The porous nature of the eggshell allows for this exchange, resulting in increased salinity within the egg. Additionally, the proteins and other compounds inside the egg can interact with the salt, enhancing the overall salty flavor. This preservation method is often used to create products like salted duck eggs.