It is rotten.
Rotting is uncontrolled microbial breakdown. Century egg curing is alkaline preservation.
No. 001 / Misunderstood Chinese Food
Wait... people actually eat this?
Yes. The century egg looks like a forbidden gemstone, smells a little dangerous, and tastes like savory egg custard with deep umami. It is not rotten. It is not buried for 100 years. It is controlled chemistry.
Not
100 years old
Most commercial century eggs cure in roughly 30 to 45 days.
Not
rotten
High alkalinity transforms proteins and fats instead of letting microbes take over.
Not
horse urine
The classic mix is alkaline clay, ash, salt, tea, and time.
What Is It?
A duck egg that got a chemistry degree.
A century egg, or pidan, is usually a duck egg cured in a strongly alkaline environment. The shell stays intact, but the inside changes completely: the white becomes a translucent amber gel, and the yolk turns dark green, creamy, salty, and deeply savory.
For people meeting it for the first time, the appearance is the whole shock. For people who grew up with it, the appeal is texture: cool jelly, rich yolk, sharp sauce, and a finish that lands somewhere between egg, aged cheese, and soy-sauce umami.
Chinese namepidan / preserved egg
Typical time30-45 days
Texturebouncy gel + creamy yolk
Best first bitewith tofu or congee
First Reaction
It looks scary because it is doing something eggs normally never do.
The white is not cooked. It becomes a gel through alkaline protein changes. The brown color comes from slow reactions between sugars and amino acids. The delicate patterns are mineral crystals growing inside the gel.
Myth vs Fact
The rumors are louder than the egg.
It is transformed.
Protein structure, pH, ions, and time reshape the egg into a new texture.
It is buried for a century.
The name is dramatic. The process is measured in weeks, not generations.
The best ones are mellow.
A good century egg tastes savory, creamy, and mineral, with only a light alkaline edge.
Visual Story
The 45-Day Glow-Up of a Basic Egg
Follow the transformation from plain duck egg to amber gel, green yolk, and pine-flower crystals.
Open the timelineDeep Dive
The Science Behind Century Egg
Alkaline hydrolysis, gelation, Maillard browning, and why it is not decay.
Read the articleGuide
All Century Egg Chapters
A tidy table of contents for the overview, timeline, science, and eating guide.
Browse chaptersHow to Eat It
Do not start with a lonely black egg on a plate.
Century egg tofu
Cold silken tofu, century egg wedges, soy sauce, black vinegar, sesame oil, scallions. Beginner-friendly and fast.
Century egg congee
Rice porridge softens the aroma and lets the yolk melt into the bowl. This is the comfort-food route.
Ginger vinegar
Sharp ginger and vinegar cut through the richness. Best once you already know what the egg tastes like.