By Anne Marie Helmenstine, Ph.D., About.com Guide to Chemistry since 2001

Lead Test of a Chinese Preserved Duck Egg
Monday October 20, 2008
Chinese preserved duck egg. (Anne Helmenstine)

Last week I discussed the legend that century eggs are preserved using horse urine and mentioned some Chinese manufacturers add lead oxide to the eggs to speed the curing process. Since lead is toxic at any dose, I decided to informally check some Chinese preserved duck eggs (century eggs) for the metal. The specific eggs I tested were made by Jiangsu Maochun Food Co., Ltd. of Jiangsu, China with ingredients listed as fresh duck egg, sodium hydroxide, tea, and salt. The test for lead was negative, so I tasted the egg. I totally understand why some people think century eggs are preserved in horse urine. That is a really accurate description of how the eggs smell. When I peeled an egg I saw the dainty frost pattern inside the egg white. Once the egg was peeled it smelled much more like an egg and less like an animal latrine. The egg white tasted similar to the white of a boiled egg. The yolk had a stronger, smoky sort of flavor.

Any food that has lye (sodium hydroxide) as its second ingredient probably isn't that good for you whether it contains lead or not, but if you can get past the idea of eating a raw egg that has been sitting around for a few months, give century eggs a try. The flavor is interesting.