When silver is mixed with sulfide decomposed by protein and amino acids in eggs, a chemical reaction will occur to form insoluble silver sulfide, which is a black compound.

In fact, the chemical properties of silver are relatively stable and generally do not react with oxygen in the air. But it will quickly react with hydrogen sulfide and elemental sulfur. In the heating state, the reaction is more likely to occur. Silver and iodine in table salt also react when heated, but the reaction speed is very slow, and the generated silver iodide is a yellow solid.

An egg and a silver spoon produce a small amount of compounds, which has no effect on the human body, so there is no need to worry about health.

But it is best not to eat preserved egg porridge with a silver spoon, because preserved eggs contain a small amount of sulfur and hydrogen, which is enough to make silver black.