There are many legends about the invention of leather eggs. The earliest written record is the seventeenth year of Emperor Xiaozong of the Ming Dynasty, Zhu Yu Shanfang Miscellaneous Department: "Chaos: take a bucket of burnt charcoal ash, add one liter of lime, add salt water, put in a pot to boil, warmed up, put on the eggs, five or seven days on the, yellow and white mixed together." This "mess" is the prototype of the skin eggs.
Notes on selecting leather eggs
It should be noted that the traditional process of making leather eggs contains high levels of lead, because the production process uses lead oxide as the main ingredient, which is used to ensure that the leather eggs do not liquefy again after maturity, and to maintain their color and flavor for a long time.
From the information released by the State Administration of Market Supervision and Administration of the People's Republic of China (AMSC) in recent years, the lead content of sampled eggs rarely exceeds the standard. So as long as they meet national standards, they are safe to eat.
When buying eggs, choose products with complete packaging, gray surface, few black spots and no cracks through regular channels. Skinned eggs should be kept in a cool and ventilated place with low temperature, and peeled skinned eggs should be consumed within two hours. If the protein of the skin egg is light green, there is an odor, indicating that it has deteriorated and can not be consumed.