Century egg, also known as preserved egg, hundred-year egg, thousand-year egg, thousand-year-old egg, and millennium egg (or Pidan in Mandarin), is a Chinese cuisine ingredient made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, lime, and rice hulls for several weeks to several months, depending on the method of processing. Through the process, the yolk becomes a dark green to grey colour, with a creamy consistency and an odor of sulphur and ammonia, while the white becomes a dark brown, transparent jelly with little flavor. The transforming agent in the centur...