Century Eggs, Centuries-old Controversies

The science behind an irrational love

Whenever I feel homesick, one of the places I want to be transported to immediately, is a traditional noodle place in Taipei, where I was raised to ask people “Have you eaten?” instead of “How are you?” when greeting them. These neighborhood spots are usually humble, without much decoration or even a clear sign at the door. Their menus consist of noodles, and only noodles. Yet you can choose to have the thin or broad variety, made with wheat flour or other types of starch; dry and mixed with various sauces, or swimming in clear soups, simmered with vegetables or beef, some with a dash of soy sauce.

To me, one of the most exciting parts of the gastronomy experience starts after you order your main. Instead of sitting around drooling at the food on the table next to yours, you exercise your legs and go to either the very front or back of the restaurant, where a display of xiao cai awaits. Literally translated as “small dishes,” they are essentially a selection of cold appetizers you can pick up yourself, bring back to the table, and munch on until your noodles arrive. From cucumbers marinated with vinegar, garlic and chili, pressed tofu stirred with peppercorn and small dried fish, to thin slices of seaweed, and salted green soybeans boiled in their pods, the choices are endless.

My personal favorite is a somewhat controversial one: chilled soft tofu topped with thinly sliced scallions and dried fish flakes, accompanied with a century egg, and finally, drizzled with some thick soy sauce. In 2011, a CNN iReport, written by amateur journalists and bloggers, published a list of the world’s most revolting food, with century eggs taking the first place. The Texas-based writer claimed that century eggs seem to be something cooked by the devil, and “taste like something that used to be an egg, but made some really horrible choices.” His remarks angered many lovers of the preserved treat, and after being accused of being ignorant and insensitive, both the network and the author issued formal apologies.

So, how can an egg spark such polarized opinions? First of all, while century eggs are made from duck eggs, or less commonly, that of chicken or quail, you will not see the typical egg white with a yellow yolk in the middle when you crack one open straight from the package. In fact, nothing will be flowing out from the broken shell, but instead, what you have in front of you is a jelly-like solid, with the egg white turned a translucent dark brown, and the yolk a deep green that is reminiscent of a marshland. Once you get over the look of century eggs, another challenge arises, directly up your nostrils — many are convinced that these eggs smell like ammonia because they are created by soaking eggs in horse urine.

Tzu-Cheng Chen, the chairman of the Taiwanese Duck Farming Association and owner of Kindly Eggs, a company that manufactures preserved duck egg products, told me, “Actually, the pH level of horse urine is not high enough to make duck eggs congealed as in the case of century eggs.” However, those averse to the pungent smell of century eggs are not completely wrong. While the process of making century eggs has nothing to do with horse urine, the eggs do contain traces of ammonia, which is a product of the chemical reaction that happens in the eggs when they are being manufactured. It is generally believed that the Chinese began making century eggs as a way of preserving the easily-rotten source of protein, and this method can be roughly dated back to the 16th century. Traditionally, raw duck eggs are coated in a paste of tea, quicklime, salt, and wood ash mixture, and then rolled in tea leaves or rice husks to prevent them from sticking together. The covered eggs are then put aside to rest for anywhere from several weeks to some months until they are ready to be consumed.

The magic that happens within the eggs as they lie quietly in their rice husk coating is basically an inorganic version of fermentation. Instead of yeast or bacteria, the active agent in this process is the alkaline materials in quicklime and ash. During the fermentation process, sodium hydroxide, a strong alkaline compound formed in the coating paste slowly seeps through the egg shells, elevating the alkaline level within the egg. This chemical stress decomposes some large proteins and fats of the egg, and breaks them into simpler, more flavorful components.

Meanwhile, the alkalinity also causes a change in the electric charge of the protein in the egg white, enabling its normally dispersed and thin strands to bond into a solid, transparent gel. A similar action takes place inside the yolk, taking away its usual graininess and replacing it with a creamy texture. Finally, the alkalinity turns some of the eggs’ proteins and fats into hydrogen sulfide and ammonia, both of which are gases that contribute to century eggs’ pungent odor.

Although century eggs are never left to ferment for a hundred years as its name might suggest, being patient with the process and not adding extra chemicals to speed it up are key to creating century eggs with a milder, less alkaline flavor. When Chen was first exposed to the preserved eggs manufacturing industry in the 70s through his father, it was common practice to add lead when preparing century eggs. Recognizing the serious effect the heavy metal could have on human bodies, Chen revamped the recipe when he took over the business from his father in 2002. Now, after soaking the eggs in alkaline solution, he leaves them to mature for at least 45 days, and the finished product can be kept for more than a year without refrigeration.

All of the century eggs that Chen’s company sells are known as “pine-blossom” eggs, a variety of the delicacy that is especially prized not only for its taste but also for its look. This type of century eggs got its name from the delicate, tiny snowflake-like patterns that can be seen on the surface of an unshelled egg. These “blossoms” are crystalized, small particles that originally constructed the eggs’ protein, and thus, having these patterns mean the protein is broken down more thoroughly than the common century egg, which also implies that it is more flavorful.

In addition to changing the formula and producing high-quality century eggs, Chen also invested in automating the production process, and invented new flavors and products that have since been patented, including the Tri-flavored Colorful Egg — this hybrid creation’s albumen smells like tea, its dark green outer yolk resembles that of century eggs, and its center yolk tastes like salted duck eggs, another popular preserved egg product.

Chen’s years of labor and innovation paid off: his factory is now one of the most modernized processed egg manufacturers in Asia, and its business has been consistently growing for the past 16 years without any active marketing initiatives. Although the CNN iReport suggested century eggs’ unpopularity abroad, Chen exports over 10 million of his carefully crafted preserved eggs to twenty countries, with the U.S., Canada, Singapore, and Australia being the largest importers.

When asked about his response to the CNN article, Chen shrugged and said, “As the chairman of the Duck Farming Association, I was constantly being asked about this, but I decided not to make a big deal out of it.” He believes that because of the media exposure, many Taiwanese actually came together to promote and create new recipes that utilize century eggs’ unique taste, leading to a new century egg boom and benefiting a lot of small duck farmers.

Although century eggs are extremely common in Taiwan and can be found in nearly every grocery store, sold in a plastic box with half a dozen individually wrapped eggs, it is rarely an everyday treat for Taiwanese. Because my family never buys them or prepares them at home, century eggs became one of those dishes that we only get to have when eating out. Because we do not eat it often, every time I have century eggs it feels special, and while going to a restaurant is not a rare event thanks to the large number of affordable, neighborhood joints, having the chance to enjoy food that does not go on my family’s table always make the experience of dining out extra special.

I remember myself feeling a perverse sense of proudness, instead of being offended, when I read the CNN iReport, perhaps pleased by my compatriots’ high tolerance to bizarre food. Even now, after several years of traveling across continents and plenty of lessons on cultural sensitivity and political correctness, I see no reason to be upset by our food being called “revolting.” Just like how century eggs are both commonplace and special to me, depending on how I look at them, people from distinct backgrounds can surely have different opinions about them. Instead of getting into a debate because of adjectives, why don’t you join me at my favorite noodle spot? I shall grab a plate of tofu with a century egg as xiao cai, and it is up to you to decide whether to dig in or not.