What Is A Century Egg And How Is Pi Dan Made?

Is it possible to keep an egg in good, edible condition safely for years? Well, we’re going to find out all about that in this article. So, keep reading.

What Is Preserved Egg?

hundred-year eggs

The Pi dan/Century Egg, also known as preserved eggs, hundred-year eggs, thousand-year eggs, thousand-year-old eggs, century-old eggs, millennium eggs, leather eggs, skin eggs, black eggs, or old eggs, These patterned eggs are regarded as having better quality than the normal century eggs and are called Songhua eggs, also known as pine flower eggs or pine-patterned eggs. The eggs turn into the color black, and they also have a dark green yolk, which really is expected of the eggs after they have been processed for weeks or, in other cases, months, in ash, clay, or even in quicklime mixed with salt.

There is a common misconception about the century eggs, though, especially the ones claiming that the eggs are more than one hundred or perhaps thousands of years old. This is untrue, and it would also be impossible to keep an egg in a safe, edible state for that long. The most common century eggs are, however, only a few months old.

The other important thing that you need to know about the preserved century egg is the fact that this egg has a very intense taste. And serving the egg is done in a way that honors traditions.

The century egg has a fascinating history, though. And in this article, we’ll take you through the basics of the preserved eggs, as well as the history of the century egg.

Century Egg History

thousand-year egg

The century eggs are believed to have originated in China’s Human province, during the reign of the Ming Dynasty, which ruled China at least 6 centuries ago. But given how old the century eggs have been around, there are many stories regarding the century eggs.

The most popular tale of the century egg is the story about a man that discovered the century eggs at an abandoned site when his home was under construction. In his discovery, the man came across duck eggs, which had been sitting in the slaked lime in the construction site for about 2 months. He opted to eat the eggs and was surprised by the taste of the eggs. It is said that he only needed to add salt to the eggs.

However, this is not the only tale about the eggs. There is also a more romantic story regarding the century egg. This tale is just as popular. The story is about a man that had left the eggs in the garden of a woman he was interested in courting. The woman didn’t discover the eggs’ existence in the ash pit until about 2 weeks later. Upon the discovery, more than half a month later, the eggs were in a good state, and it led to the discovery of the century eggs.

There is also the story of the farmer who came across duck eggs that had been preserved naturally in water plus slaked line, which is typically calcium hydroxide.

Despite these fascinating monikers of the century eggs, the millennial eggs, or the 100-year eggs, the ‘so-called century egg’ is still metaphorically a Century egg, because in most cases, these eggs are more than a few weeks or months old.

The century egg is also known as the pine-patterned egg because of the pine branch shape and the woodland-looking and intricately patterned features on the egg white and the surface of the egg. It is a great dish throughout China, but also in the rest of East Asia.

Historically, this egg dish was created because food needed to be preserved, and all extra foods would be preserved. Preservation of the eggs led to the creation of the century eggs which are preserved in some sort of alkaline paste.

However, despite the documented details about the eggs, the real history of the eggs remains largely unknown, and the records from the Ming Dynasty represent the earliest known records of the existence of the century eggs. And though most of the century eggs were created and preserved by the villagers and farmers hundreds of years ago, the appearance of eggs in Hong Kong menus only dates back to the 1940s.

How To Make Century Eggs

The century eggs are created from either duck or chicken eggs which are preserved in an alkaline solution for an extended duration.

Traditionally, the preparation of the century eggs involves putting the eggs in a mixture of salt, lime, as well as ash. Afterward, the eggs and the mixture are wrapped in the rice husks for weeks or even months.

The modern method is different, though, and it is also very straightforward, with most of the ingredients substituted for the ingredients used traditionally. So, century eggs are today made of sodium carbonate, calcium hydroxide, and table salt. These are all wrapped in plastic, and all you will need to do is to peel and then rinse the eggs once the eggs are ready to be eaten.

thousand-year-old eggs

The biggest misconception about all this is that the century eggs would be spoilt after all that time, but this is not really the truth. Instead, the eggs in the alkaline solution are only preserved. The eggs are also safe and free from mold and bacteria, which is why the century eggs are such a big deal.

How To Cook Century Egg

millennium eggs

If you have been to Hong Kong, you may have learned that the century eggs are sold in many restaurants, some of which specialize in the best of century eggs. These eggs feature proportionately larger eggs yolks, but they often remain runny and greenish-yellow and also surrounded by specific concentric rings in navy blue, brown, and green. And you may be interested in learning about the eggs or even tasting them. But how do you cook the century egg?

Well, as mentioned above, the eggs are not cooked; they are preserved in an alkaline solution and are packed away in rice husks for weeks or even months, in even cases. In other words, the century eggs are cured eggs and not really cooked eggs – at least not in the traditional sense.

If you want to make the century eggs at home, follow the following steps:

  • Mix ash, salt, clay, water, and quicklime to make a kind of paste
  • Apply a thick layer of the paste to completely cover the raw eggs.
  • Now roll these eggs in the rice grain husks. This prevents the eggs from sticking with each other.
  • Once done, store the eggs in an airtight container, and then store the eggs in the dark. Let them sit for several weeks.

How To Eat Century Egg

skin eggs

Before we look at how to eat the century eggs, how about a look at how the century eggs taste?

Well, many people have a very strange first impression of the century eggs, but during the preservation or the preparation process, the proteins and fats that are initially flavorless are broken down, and they become very flavorful. During the breakdown process, the egg white takes on a dark-brown appearance, and it looks like this translucent jelly that is salty. The egg yolk, on the other hand, takes on a dark grey or green color.

Once ready, the eggs have a consistently smooth and very creamy feel and more of a succulent taste. It is often eaten with tuna, and it will leave a silky taste in the mouth when you eat it.

But even if you can stand the taste – most people consider the taste of the century eggs an acquired one – the smell of the eggs is very strong, as expected. The strong smell, along with the intense flavor of the eggs, comes from the hydrogen sulfide and ammonia present in the eggs.

Why Century Egg Is Black?

black eggs

The century egg has a distinct black hue because of the Maillard reaction, which is a natural browning effect, often accelerated by the highly alkaline environment that the eggs are prepared in. The sodium hydroxide that the century egg is made in is what increases the discoloration of the eggs. It also breaks down the protein in the eggs into amino acids and glucose that makes the eggs more flavorful.

To enjoy the eggs, you may have to combine them or serve them with roasted pepper or eat them with silken tofu.

But you will need to slice the eggs into small wedges first – the eggs may stick on the knife, but this is normal and expected.

Next, roast some bell peppers, then slice them thinly in strips and serve them with the eggs.

Note that you don’t have to cook the eggs after taking them out of the preservation container.

Is Century Egg Healthy?

old eggs

Yes, the century egg is not only healthy but also very nutritious to your health thanks to its richness in amino acids, iron, and vitamin E.

Unfortunately, the denatured proteins after the preservation are not easily absorbed in the gut.

Century Egg Pros And Cons


  • The eggs are tasty, with a smooth, creamy consistency
  • The ammonia and hydrogen sulfide add flavor
  • The broken-down proteins and amino acids are very beneficial to the body
  • Great source of vitamins D and E.
  • Excellent selenium source


  • The denatured proteins are not absorbed in the gut easily
  • They are an acquired taste
  • The smell is too strong

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