The thousand-year-old egg (video)

WASHINGTON — Century eggs, or pidan, are a preserved food made by fermenting duck eggs in alkali. The green and black color of these eggs is not very appealing at first blush, and the smell is even worse. However, this Ming dynasty innovation effectively extended the shelf life of eggs and has been adopted as a beloved comfort food in China and throughout the world. Reactions explains the chemistry behind this unusual culinary offering: