What are salted duck eggs, and why are they orange?

Oct 05, 2020

Salted duck eggs are a classic Chinese side dish, and a traditional way to preserve fresh eggs.

Salted duck eggs are a mainstay in Chinese cuisine. They’re enjoyed as a side dish to porridge; as an ingredient in mooncakes, round pastries consumed during the Mid-Autumn Festival; and sprinkled on lobsters and tofu as a coating.

In terms of flavor, the egg white has a stinging saltiness, while the yolk is fatty and bursting with umami. The taste is so beloved in Asia that it’s even been used in potato chips.

Salted egg-flavored chips from Irvins.
Salted egg-flavored chips from Irvins.

The most famous salted duck eggs come from Gaoyou in eastern China. The city is proud of its ducks, which produce eggs with a rich orange-red yolk.

“The ducks here are one of the top three duck breeds in China,” brags Zhou Yujun, the technical lead at Hongtaiyang Foods, which produces 1.2 million eggs a day during high season in the summer.

(Read more: Why are century eggs black? The science behind their color)

Salted duck eggs are the result of an age-old method of preserving fresh eggs. Traditionally, they’re made by covering eggs with a clay made from plant ash, dirt, salt, and water.

The eggs are then left to sit for 30 to 40 days, depending on the temperature.

While they sit, water exits the egg and is replaced by salt, in a process known as osmosis.

This solidifies the yolk, leaving behind the characteristic fatty yolk of salted duck eggs.

The yolk in salted duck eggs are completely devoid of water, leaving behind just the fat.
The yolk in salted duck eggs are completely devoid of water, leaving behind just the fat. / Photo: Shutterstock

Nowadays, many eggs are made in factories, with a vacuum seal instead of clay. For the average consumer, there’s not much of a difference, but Zhou, who’s a professional, can tell the difference.

“Because the plant ash version is alkaline, the eggs are drier and taste better than the vacuum-sealed versions,” he says.

And the reason why the yolk is orange?

“Our ducks in Gaoyou are all raised by the river,” Zhou says. “They eat a lot of little fish, shrimp, snails, and water grass, which has a lot of beta carotene.”

Beta carotene is the same pigment that turns carrots orange. Eat enough of it, and you’ll be orange, too.



Producer: Clarissa Wei

Videographer: Shirley Xu

Editor: Joel Roche