Preserved eggs are the traditional food of our people. Because of its unique flavor, excellent taste and long shelf life, it is deeply loved by people. Do the students know? In fact, the process of processing fresh eggs into preserved eggs is a complex chemical process. Strong alkali (sodium hydroxide and potassium hydroxide) in the ash material permeates into the egg yolk and egg white from outside the eggshell, and reacts with protein in the egg yolk and egg white, so that protein decomposes, solidifies and releases a small amount of hydrogen sulfide gas. At the same time, the infiltrated alkali further reacts with the amino acids decomposed by protein, and the crystals of the generated salt condense into beautiful shapes in the egg white, like blossoming "pine flowers". Hydrogen sulfide gas reacts with minerals in egg yolk and egg white to generate various sulfides, so the colors of egg yolk and egg white change. Egg yolk is dark green and egg white is special tea green. Salt can shrink preserved eggs from eggshells, increase flavor and prevent corrosion. The added lead can accelerate the ripening of preserved eggs and promote the shrinkage and shelling of preserved eggs. Tannin and aromatic oil in tea can solidify and color protein, and increase the flavor of preserved eggs.