Centennial eggs are said to have originated in Hunan, China, during the Ming Dynasty, approximately six centuries ago.

The most popular story says that a man discovered them during the construction of his house, when he saw duck eggs that had been in slaked lime for two months. He ate them and enjoyed the taste, so he added salt to improve the taste.

Another, more romantic story is that of a man who left eggs in the garden of a woman he wanted to court. However, she did not discover them until she cleaned the ash pit half a month later. In this way, centenary eggs were created.

It is also called 'pine pattern egg' because some of them have pine branch-like patterns in the egg white. This Chinese dish is not only famous in China, but throughout East Asia, where they have their own names for it.

This dish was most likely created during the need to preserve eggs in the past, so they were covered with alkaline clay, leading to the creation of century eggs.

TRADITIONAL METHODS OF PRODUCTION OF CENTENARY EGGS

Most recipes start with a duck egg, but you can also use a chicken, goose or quail egg. Instead of using just clay, a mixture of wood ash, calcium oxide (also known as quicklime), and salt is included in the coating mix, which increases the pH of the sodium content. 1.4 kg of tea is infused in water and 1.4 kg of calcium oxide, 4.1 kg of sea salt and 3.2 kg of burnt oak ashes are added, mixed until a smooth paste is obtained. Each egg is individually coated by hand, with gloves on to protect the skin from chemical burns. It is then rolled in rice husks, to prevent the eggs from sticking together, before the eggs are placed in cloth-covered jars or densely woven baskets. The rice hulls prevent the eggs from sticking together.

MODERN METHODS OF PRODUCTION OF THE CENTENARY EGG

Century eggs are made from pasteurized or homogenized whole eggs that have been soaked in an alkaline solution containing various chemicals such as potassium bicarbonate, sodium carbonate, sodium hydroxide, and/or calcium hydroxide. The mixture may also contain other ingredients including sugar, gelatin, glycerin, citric acid and food coloring. After leaving them undisturbed at room temperature for about two months, they will be ready to eat.

The short answer is yes. Centennial eggs, like many preserved foods, are safe to eat, but it is important to check them for signs of spoilage before eating. While the smell of ammonia will always be present in century eggs, an excessively bad ammonia smell or a moldy stench are signs that something has gone wrong. The shell should be visibly intact, with no cracks, holes or dents. When shaken or tapped, there should be no rattling sound.

It is also important to obtain century eggs from a reliable source. It used to be common to use lead oxide during the curing process, which creates a century egg that is considered more desirable but also has the unfortunate effect of being toxic to humans. While there are food safety regulations in China that restrict toxic levels of lead in food, some century egg producers ignore these metrics for the sake of a “better” end product. The good news is that most century eggs available now are lead-free.

There are malicious rumors claiming that century eggs are soaked in horse urine, which is of course a complete fabrication. Horse urine is not even alkaline, something needed to make century eggs. One reason for the misunderstanding could be that in Thai and Lao, the local words for century eggs literally translate to "horse urine eggs." Others might confuse it with "virgin boy eggs," which are prepared with urine, but not from horses.

It is important to clarify that centenary eggs have no relationship with urine in their manufacturing process. They are produced by preserving eggs in an alkaline mixture, usually based on clay, ash, salt and lime. This process changes the texture and color of the egg, but does not involve the use of urine or any other such liquid.