The earliest producing areas of preserved eggs are Weishan and Weishan Lake brand preserved eggs. According to historical records, it has a history of more than 500 years since the beginning of Ming Dynasty, and it is still an important producing area of preserved eggs.

Preserved eggs may have evolved from salted duck eggs recorded in the Book of Qi Yaomin in the Northern Wei Dynasty. A clearly recorded preserved egg was written in the 17th year of Emperor Xiaozong of the Ming Dynasty (1504), in the house miscellaneous department of Zhuyushan.

Making principle of preserved eggs:

Preserved eggs use eggs in alkaline solution to change the characteristics of protein gel into elastic solids. But if the formula of preserved eggs is not well controlled, protein will be hydrolyzed in alkaline solution, and protein will be denatured into protein, so it can't be eaten.

If the eggshell cracks or the formula is not well controlled, the hydrogen sulfide in the egg will overflow and turn golden yellow. Normal preserved eggs are dark green, pine-flowered and elastic.