What is a thousand-year-old egg?

In this brief guide, we’ll address the search query: “What is a thousand-year-old egg?” Also, we’ll explore where the thousand-year-old egg dish is from,  how it is prepared, what its nutritional content is, and what are some things to consider before enjoying this dish. 

What is a thousand-year-old egg? 

A thousand-year-old egg alludes to a Chinese delicacy, which can also be referred to by many other names. These include a century egg, old eggs, black eggs, hundred-year-old eggs, etc. 

In a more definitive sense, thousand-year-old eggs are made by curing either chicken, quail, or duck eggs in a mixture made with various ingredients that will ultimately transform the egg into one resembling an antique. 

Notably, the egg yolk will transition to a green or gray shade and have a different, creamier consistency. The egg’s white will be transformed into a dark brown shade and have a more gelatinous aspect.

The preparation of century eggs usually has cultural aspects, such as aging the eggs in clay and rice hulls, but thanks to our understanding of chemistry and the changes these eggs undergo, it’s possible to replicate the effects using ingredients such as salts, hydroxides, and carbonate, while letting them age in a designated spot. 

However, thousand-year-old eggs should only be sourced from reputable producers, as some unscrupulous characters may economize both in ingredients and timespans, resulting in subquality, and even potentially noxious eggs.  

Where is the thousand-year-old egg from? 

Thousand-year-old eggs, also known as century eggs, originated in China. Though there aren’t any exact records to uphold their precise origin, they’re believed to have originated in Hunan, a landlocked province in mainland China, around six hundred years ago. 

There are different stories surrounding their origins, and most allude to an accidental, serendipitous discovery. 

In spite of their many monikers, thousand-year-old eggs are only aged for just a few weeks, and they’re thought to be the product of a preservation method that cured eggs, rather than preserved their freshness. 

How is a thousand-year-old egg prepared? 

Thousand-year-old eggs are prepared by preserving eggs (they can be chicken eggs, duck eggs, or even quails) in a mixture that has a high pH. 

The alkaline solution will cure the eggs and bring about a series of changes that will result in the eggs looking aged. 

Nowadays, the process can be carried out by preparing a mixture of sodium chloride (table salt), sodium carbonate, and calcium hydroxide, coating the eggs in it, and wrapping them in plastic cling-wrap 

Contrary to popular belief, these eggs are neither spoiled nor fermented–as no microorganisms will have played a part in the process. 

What is the nutritional content of a thousand-year-old egg? 

A 71-gram portion of a thousand-year-old egg (or a century egg) will provide (on average)

  • 130 calories – of which 87 are sourced from fat,
  • 9 grams of protein
  • 9.6 grams of fat (15% of the RDI) – of which 2.6 grams are saturated fat (13% of the RDI), 0.9 grams are polyunsaturated fat, and 4.6 grams are monounsaturated fat.
  • 1 gram of carbohydrates – of which 0.7 grams are sugars
  • 619 milligrams of cholesterol (206% of the RDI)
  • 529 milligrams of sodium (22% of the RDI)
  • 155 milligrams of potassium (4% of the RDI) 

Additionally, the same portion will provide 9.4% of the recommended daily intake of vitamin A, 3.5% of the RDI of calcium, and 15% of iron. 

What should I consider before eating a thousand-year-old egg? 

When eating thousand-year-old eggs (century eggs), it’s important for readers to bear in mind that they are high in cholesterol and sodium, and therefore, may be contraindicated for patients who are at risk or have been diagnosed with heart disease, circulatory problems, and other disorders. 

It’s also important for our readers to purchase them from reliable, reputable sources. There have been incidents in the past, where to speed up the process, some manufacturers resorted to switching ingredients in the formula, and the results were potentially noxious

We encourage our readers to be mindful of their daily intake of calories and to consume dishes that are high in both sodium and cholesterol sparingly. 


In this brief guide, we’ve addressed the search query: “What is a thousand-year-old egg?” Also, we’ve explored where the thousand-year-old egg dish is from,  how it is prepared, what its nutritional content is, and what are some things to consider before enjoying this dish. 






Leave a Comment