Century eggs, also known as thousand-year eggs or preserved eggs, are a traditional Chinese delicacy that have a unique and intriguing production process. Despite their name, they are not actually aged for centuries, but rather undergo a preservation method that transforms the eggs into a gelatinous and pungent treat.

The process of making century eggs involves a few key steps:

1. Coating the eggs: Fresh duck, chicken, or quail eggs are carefully selected for this process. The eggs are first coated in a mixture of clay, ash, salt, quicklime, and rice straw.
2. Wrapping the eggs: After being coated, the eggs are individually wrapped in a layer of rice husks or a mixture of wood ash, salt, and charcoal. The wrapping process helps to regulate moisture and prevent spoilage during the fermentation process.
3. Fermentation: The wrapped eggs are then placed in a cool, dark, and well-ventilated environment, such as a cave or a specially designed room. They are left to ferment for a specific period, usually around several weeks to several months, depending on the desired level of preservation.
4. Unveiling the century eggs: Once the fermentation period is complete, the eggs are carefully unwrapped and cleaned. The outer coating, which has hardened during the fermentation process, is removed to reveal the transformed century eggs.

The unique preservation process of century eggs involves several chemical reactions. The alkaline materials used in the coating, such as quicklime, raise the pH level of the eggs, creating an alkaline environment. This alkaline environment promotes the breakdown of proteins and fats in the eggs, resulting in the formation of ammonia and various other compounds.

The ammonia, along with other chemical reactions, contributes to the distinct flavors and odors associated with century eggs. The eggs develop a gelatinous texture and a dark-colored yolk, while the egg white turns into a translucent jelly-like substance.

It's important to note that the consumption of century eggs is a matter of personal preference due to their strong smell and acquired taste. They are commonly enjoyed as a topping in congee (rice porridge), in various cold dishes, or as a snack.

References:

1. Smithsonian Magazine. (2021). The Science Behind Century Eggs. Retrieved from https://www.smithsonianmag.com/science-nature/science-behind-century-eggs-180977321/
2. Chen, C. (2019). The Making of Century Eggs. The New York Times. Retrieved from https://www.nytimes.com/2019/04/30/t-magazine/century-eggs-china.html