The Mystery of Century Eggs

The Mystery of Century Eggs

Story by Patrice Lewis

EGGS ARE NOTHING IF NOT versatile, embellishing meals for appreciative diners the world over. What happens when your hens lay more eggs that you can eat? Even more challenging, what if you have no refrigeration to handle the extras?

Different cultures, the world over, have found ingenious ways to preserve
eggs. One such technique is the Chinese “century egg.” Alternately termed hundred-year eggs, thousand-year eggs, millennium eggs, or black eggs, these are simply chicken or duck eggs preserved through the chemical action of ash, salt, clay, and quicklime.

Centuries Old

Century eggs are said to date back 600 years or so ago in Hunan province, during the Ming Dynasty. There are always “origin” stories that try to explain how something got started. There are many for the century
egg, from a farmer accidentally leaving eggs in slaked lime to a romantic boy leaving eggs for his intended in an ash pit. Of course, no one knows. But
here are some distinctive features to the century egg that have been noted
for, well, centuries, most coming from the salt used in preservation.

Sometimes what look like tree rings will be obvious when the eggs are cut
length-wise. Most obvious are the salt crystals that linger on the outside of
the egg, and look like pine tree bows, or snowflakes.

Traditional century eggs are covered in mud, ash, rice hulls, and other materials that leave spots on the eggshell, darken, and preserve the color of the egg.

Although century eggs are mostly associated with China, similarly preserved eggs are consumed in Japan, Vietnam, Thailand, Taiwan, Laos, Cambodia, and other Southeast Asian nations.

The Process

The process of making century eggs can be divided into traditional vs. modern (commercial) techniques. Historically, eggs were soaked in an infusion of tea, then plastered (mudded) with a mixture of wood ash (oak was considered best), calcium oxide (quicklime), and sea salt. The alkaline
salt raises the pH of the egg to around 9 to 12, breaking down some of the
proteins and fats and lowering the risk of spoilage. The plastered eggs are
rolled in rice hulls to keep the eggs from sticking together, then placed in tight baskets or jars. The mud takes several months to dry and harden, at
which point the eggs are ready to eat.

It’s not surprising that modern chemistry had an affect on this cottage industry, transforming it into routine commercial production. The critical step is introducing hydroxide and sodium ions into the egg, and this process is accomplished with both the traditional and the commercial methods. Chemically, the process can be sped up by using the toxic chemical lead oxide, but for obvious reasons, this is illegal. If you’re going to try your hand at making century eggs at home, food grade zinc oxide is a safer alternative.

The salt crystals left on the egg whites make a classic “pine tree” pattern known as Songhua.

Appearance and Taste

The colors of century eggs are striking. Rather than a white shell with yellow and white inside, the egg shells become speckled, the yolk turns anywhere from dark green to grey with a creamy texture, and the egg white turns dark brown and gelatinous. This is known as the Maillard reaction, a
browning effect in a highly alkaline environment. The most highly prized
century eggs (called Songhua eggs) develop a striking crystalline pine tree
pattern. The egg white acquires a salty taste, and the yolk smells of ammonia and sulfur with a flavor described as “complex and earthy.”

If you’re turned off by the thought of consuming one of these delicacies, bear in mind a century egg is not bitten into like a hard-boiled egg after being dipped in salt. The egg may be sliced and arranged on a plate like the petals of a flower, with an attractive garnish in the center. Or it might be divided into rounds, dressed with herbs and spices, and served as an hors d’oeuvre. Or it might be cut in half and embellished with caviar and seaweed. Century eggs are also chopped and added to rice dishes, soups, stir-fries, congee dishes, and other culinary specialties.

Still, century eggs are an acquired taste outside the palates of most westerners. However, keep in mind that in 2021, Chinese people consumed
about 2.8 million tons of Songhua eggs (century eggs with the pine pattern).
Read that again: 2.8 million tons. That’s a lot of eggs.

“At the very first bite, you may feel it has the accents of sulfur and ammonia,” explains one enthusiast. “But after the first taste, you will enjoy a world of highly flavorful and umami components which are denatured from egg proteins under the stress of higher pH value.”

While it’s doubtful century eggs will ever develop this level of enthusiasm
in the West, it’s a testament to how creative many cultures around the world can be when it comes to preserving excess eggs.

PATRICE LEWIS is a wife, mother, homesteader, homeschooler, author, blogger, columnist, and speaker. An advocate of simple living and self-sufficiency, she has practiced and written about self-reliance and preparedness for almost 30 years. She is experienced in homestead
animal husbandry and smallscale dairy production, food preservation and canning, country relocation, home-based businesses, homeschooling,
personal money management, and food self-sufficiency.
Follow her website or blog

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