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Cracking the mystery of the Century Egg

 

LEGEND HAS IT THAT 600 years ago, sometime during the Ming Dynasty, a Hunan peasant while renovating his home discovered his ducks had left some of their eggs in a shallow pool of slaked lime (quicklime mixed with water) that was being used to make mortar (cement). The eggs were in the pool for over two months. Curious, and probably not wanting to waste anything that could potentially still be food, he ate the eggs and to his surprise, exclaimed: “Hey, this stuff is good!”

A plateful of century eggs, made the traditional way of using clay and the new way by using wax. In the bowl are the results, with the accompaniment being pickled shallots.
A plateful of century eggs, some shelled, some unshelled, some made the traditional way Vs the new way using wax. In the bowl are the peeled results, with the side accompaniment being pickled shallots, although pickled ginger is usually the preferred condiment.

Well, maybe he didn’t say those words exactly but he liked what he discovered and started making more of those eggs, tweaking the recipe here and there and adding more salt for oomph and flavour. Before he knew it, century eggs were born! They were “born” so well, they took China by storm, became a delicacy sought after by most of the world and spawned a whole new industry that thrives till this very day.

An Egg known by any other Name

Some people say century eggs or “pidan” or “pei darn” in Cantonese are a fowl (foul) Asian invention, they look putrid and smell awful with a taste to match but actually, ‘one man’s meat is another man’s poison’ as they say, so to each  his own. But most epicurean adventurers would have tasted them anyway ─ in broth or congee or on an ‘as-is-where-is’ basis where their pungency was savoured, often with counterpoint notes of flavour provided by slices of sweet and tangy preserved ginger.

egg on square laceCentury eggs can be re-concocted as many an exotic dish ─ deepfried, baked, or whatever with other ingredients.  In Taiwan, the favourite way to eat it is by chopping it up to little pieces to top cold white tofu alongside chopped spring onions, roasted garlic, sesame oil and soy sauce.

These ‘Fowl’ Eggs are an Acquired Taste

Usually made out of duck, quail and lately, chicken eggs, century eggs are an acquired taste (much like durian). It takes a braveheart to bite into one because they are suspiciously black in colour, strangely jellified with a squishy yolk that has a funny taste and there’s no mistaking the odour. Century eggs give off a sharp sulphur and ammonia gas ─ the result of being fermented and preserved  in the airless encasing of clay, wood ash, quicklime salt and rice hulls for weeks, sometimes months. This “curing” process raises the eggs’ alkaline content to somewhere like 9 to 12 ─ good for your health and sex life people say. In other words, with their modified chemical compounds, century eggs are highly alkalined, highly altered eggs which is why they deliver such a punch to the olfactory senses. But that’s exactly why they are such a delicacy. You’ll either hate it or love it but if you give it half a chance, it’s a taste that could grow on you.

Nicknamed Poison Eggs at Home

The new style of making century eggs. Gone are the clay and rice husks. The covering employs non-porous materials such as wax instead.
The new style of making century eggs. Gone are the clay and rice husks. The covering employs non-porous materials such as wax instead. This century duck egg is covered in wax.

My daughter, then 12 years old at the time, coined the term “Poison Eggs” when she first tried them. She still calls them Poison Eggs till today and actually, she’s not that far wrong. Century eggs were later found to be high in lead and other heavy metals due to unscrupulous manufacturers using lead oxide to speed up the curing.

But thank goodness for business conscience that led to lead-free modern day practices, a lot of century eggs are cured lead free these days, like those made by Wasson Food Tech Sdn Bhd (the first maker of chicken century eggs in Malaysia, did you know?), and Lau Kon Hing Sdn Bhd.  They make huskless, clayless century eggs covered in wax instead. (A heads up: That’s the clue for lead free eggs).  But always look for labels that say “lead free” just in case; it’s for your own peace of mind and health.  Most local manufacturers will adhere to food safety laws anyway, just beware of those imported from China.

Look at the beautiful patterns on this century egg. This one has exceptional patterns because it has been purposely made that way. However, if you look closely at any century egg, the patterns are also present but perhaps less vividly and in lesser numbers.
Look at the beautiful patterns on this century egg. This one has exceptional patterns because the recipe has been purposely altered to produce the dendrite effect. However, if you look closely at any century egg, the patterns will also be present but perhaps in less defined vividness and in lesser numbers.

Although the name implies it, we are not fooled into thinking that century eggs are really 100 years, 1,000 years or even a millennium old. In fact, they are really just a few weeks to two months old depending on the method used by their manufacturer in their curing.

New Vs Old Methods

Traditional methods use tea, sea salt, oak ash, quicklime and clay, plus a long period of fermentation to produce the eggs.  This method is still widely practiced but understanding of the chemistry behind the formation of century eggs has led to simpler recipes nowadays.

For instance, soaking the eggs in a brine of salt, calcium hydroxide and sodium carbonate for 10 days followed by several weeks of aging while wrapped in plastic or wax achieves the same effect although there will be some modifications to the flavour in the end result.

Taking the Piss out of the Eggs

Because they reek of ammonia, there’s a rumour that says the eggs were made by soaking them in horse urine. In fact, in Thailand, century eggs are called “khai yiao ma” which means Horse Urine Egg.

Well, let’s take the piss out of that equation then. No urine of any sort has ever been involved in the making of our favourite misnomer. The eggs are made by getting them plastered in the precisely-calibrated clay mixture, then rolled over rice chaff to keep them from sticking on to one another before they are placed in cloth covered jars for two months to dry the clay and to ferment the eggs.

Look closely to the right of the picture. The dendrite patterns are visible. For this reason, century eggs are also called pine-patterened eggs or "songhua dan".
Look closely to the right of the picture. The dendrite patterns are visible on this egg too, as they are on most eggs. For this reason, century eggs are also called pine-patterned eggs or “songhua dan”.

Two Mysteries Unravelled

If you take nothing else away from this information, at least now you know why the eggs are covered in rice husks. It’s simply to prevent them from clumping together in the mud bath.

Furthermore, you’re about to learn something magical about the eggs too. Such as why many of them exhibit intricate snow-flake or tree branch-like patterns just beneath the surface of the egg whites.  These suspended patterns inside the egg are like works of mysterious 3D art. Never seen these patterns? Look closely, preferably under light. In fact, the patterns are so commonplace, century eggs are sometimes called “Songhua dan” or pine-patterned eggs.

There’s no mystery in the artform but science. The patterns are caused by crystalline dendrites of the various alkaline salts in the egg. The more salt there is in the curing solution and the more the temperature changes during the fermentation, the more these patterns will emerge.

And there you have it. Another mystery cracked.

And now you can sit back and enjoy your century egg or two, knowing that you know all about its 100-year old mystery now.

What you see caked around traditionally-made century egg are rice husks. They are rolled into the clay to prevent the batches of clay-plastered eggs from sticking to one another
What you see caked around traditionally-made century eggs are rice husks. They are rolled into the clay to prevent the batches of clay-plastered eggs from sticking to one another.

Pros and Cons of New Vs Old style Century Eggs

Clayless huskless waxed century eggs (both chicken and duck) are less pungent and less flavourful than the traditionally-made clayed eggs

  • Clayless huskless waxed century eggs are less messy and more convenient to de-shell. Just knock and peel as you would a hard boiled egg.
  • Chicken century eggs are wobblier and less firm than century duck eggs. They are also lighter in taste than duck eggs.
  • Quail century eggs are a lot of work as they are still made traditionally, encased in hard clay and rice husks. Plus, they are very small comparatively.

 

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