Quail Eggs

The traditional method for producing century eggs is a development and improvement from the aforementioned primitive process. Instead of using just clay, a mixture of wood ash, quicklime, and salt is included in the plastering mixture, thereby increasing its pH and sodium content. This addition of natural alkaline compounds improved the odds of creating century eggs instead of spoilage and also increased the speed of the process. A recipe for creating century eggs through this process starts with the infusion of three pounds of tea in boiling water. To the tea, three pounds of quicklime (or seven pounds when the operation is performed in winter), nine pounds of sea salt, and seven pounds of wood ash from burned oak is mixed into a smooth paste. While wearing gloves to prevent the lime corroding the skin, each egg is individually covered by hand, then rolled in a mass of rice chaff to keep the eggs from adhering to one another before they are placed in cloth-covered jars or tightly woven baskets. The mud slowly dries and hardens into a crust over several months, and then the eggs are ready for consumption.

Even though the traditional method is still widely practiced, modern understanding of the chemistry behind the formation of century eggs has led to many simplifications in the recipe. For instance, soaking the eggs in a brine of salt, calcium hydroxide, and sodium carbonate for 10 days followed by several weeks of aging while wrapped in plastic is said to achieve the same effect as the traditional method. This is because egg-curing in both the new and traditional methods is accomplished by introducing hydroxide ions and sodium into the egg.