Century Eggs

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Introduction: Century Eggs

About: I'm Mike and I make crazy things at Instructables HQ in San Francisco. Follow me and try a few of my projects for yourself!

Whether you call them century eggs, hundred-year eggs, millennium eggs or whatever, these outlandish ova are a Chinese delicacy dating back centuries to the Ming Dynasty. The boastful name suggests these eggs take forever to make, this is a misnomer. Century eggs take about 4-5 weeks to make, a few minutes to work up the courage to open, and a few seconds to eat.

Traditionally century eggs were made by preserving chicken or duck eggs in a mixture of salt, lime and ash, then wrapping in rice husks for several weeks. During this time the pH of the egg raises transforming the egg, the chemical process breaks down some of the proteins and fats into smaller, more complex flavours. After curing the yolk of the egg turns a dark green and has a creamy consistency, while the white turns amber and is gelatinous. 

I chose a more modern method to achieve the same results: a salt and lye pickling solution, and encasing in modelling clay. After about a month my eggs were ready, and I'm happy to say they turned out perfectly!

Want to make your own? Of course you do! 
Enough talk, let's make some eggs!


Step 1: Supplies + Materials

supplies:
  • 100% lye/caustic soda (NaOH - sodium hydroxide)*
  • salt (NaCl - sodium cloride)
  • chicken egg (duck or quail egg)
.
materials:

* Technically lye is a corrosive, not poison. Though, it' can be labelled as either. It's incredibly dangerous to handle and can cause severe burns with contact to skin, there's also an inhalation risk. Use gloves and a respirator.
There's plenty of other foods that are made/prepared with lye, but use caution and common sense.
Always use pure, 100% lye (sodium hydroxide).

Step 2: Prepare Pickling Solution

Start by making the pickling solution, here's the basic breakdown:
  • 1L  - Water
  • 42g - Sodium hydroxide(NaOH)   (lye)
  • 72g - Sodium chloride(NaCl)   (salt)
On a scale weigh out the lye and salt. Over low heat dissolve the salt and lye completely in water. Bring the solution to a boil and allow it to cool down before use.

Place raw eggs into glass jar and pour the cooled pickling solution over eggs. Ensure all eggs are completely submerged. 

Step 3: Store

I wrote the date of submerging these eggs on my label, as well as the expected dates for encasing in clay, and eventual consumption. Label jar and store in a safe place, like the corner of your desk, so all your coworkers can gawk in disgust (or silent admiration). I also added a warning so my coworkers wouldn't mess with the jar while the eggs were pickling.

Leave eggs at 15-20°C (60-70°F) for about 10 days. Keep an eye on them to ensure they don't pop up above the solution and stay submerged.


Step 4: Remove From Brine

After about 10 days it's time to remove the eggs. Carefully pour out brine and pick out eggs, rinse with water then towel dry. The shells should still be hard.

You should be able to see some discolouration through the shells. 

Step 5: Encase

Traditionally century eggs were rolled in mud then wrapped in rice husks and buried for a few more weeks. In this modern version I simply wrapped the eggs in several layers of clear plastic wrap then encased in modeling clay. This inhibits oxygen from reaching the eggs while they cure.

Be careful when encasing in clay as not to break the eggs. After wrapping I put all the eggs into a resealable bag and left for another 2 weeks. 

Step 6: Crack Open

After about a month from the when the eggs were first put into the brine solution it's time to open them up. Carefully remove the clay encasement and the plastic wrap, then tap the egg to break the shell and gently peel away. The eggs should be completely transformed!

The whites of the eggs will now be a jelly-like translucent amber colour and the yolks a very dark green and with a texture much like a hard boiled egg. Take a look at picture 2 in this step to see the different consistency between the yolk and white in my egg-xperiment.

Step 7: Serve!

Century eggs are typically served mashed up in soupy rice. I made a steamy bowl and served it to my friends.

The taste was...interesting. The appearance is deceiving and almost put me off eating it altogether, but once I ate some it wasn't that bad. It tasted kind of like a hard boiled egg, only with a more complex flavour and a slightly mineral/metallic taste. I'm happy I tried this and think I would probably eat it again. You know, sometime later (much, much later).



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74 Comments

Why didn't you just go down to your local Chinatown restaurant and just order a dish of the real thing made by Chinese? Or in the USA you can probably just buy "Century Egg" on Amazon these days. Cheers!

2 replies

Why just buy everything on Amazon. Isn't this why Instructables is here?

Where's the fun in that?

Please dont eat anything that required drain cleaner to make. If this isnt illegal it should be.

5 replies

Please change the image you have displayed for ingredients.
Yodu are suggesting for people to use drain cleaner for this by using that image, and that is not safe.
100% lye doesnt mean its safe to use in food apications.
You need "FOOD GRADE" lye. Its even listed in the wiki page you linked to.

Hey, i started a batch yesterday and one of the eggs has broken in the jar (i was tipping it round to ensure even coating of solution). Are the other eggs safe? Will the lye kill off all the possible contaminants from the raw egg that is now in the solution?

I wouldn't eat the broken egg, but the others should be fine.

It should be illegal that you are allowed to post such rubbish. These are eaten since ancient times. Shame on you!

I have been making -- and eating -- these for years. After the brine I seal each one in a little bag with my vacuum machine. Works perfectly well

You do not need to heat the solution... in fact do NOT pour lye into heated solution because they will react vigorously. The salts will dissolve in cold water (lye will warm it up a bit).

Also the eggs will float since you just made the solution denser by adding salt and lye to it..

As those eggs aren't cooked, I am courious about germs.
Whats about bacteria like salmonella? Are they gone?

6 replies

Century egg is pickled, meaning they are soaked in a strong brine solution that kills bacteria. I do not think bacteria can live in an extremely high ph environment, not to mention how salty it is.

I have seen century egg sold in stores here in the states refrigerated and I do not think it's necessary since those eggs are preserved, so it will not spoil unless the shell broke.

It's a bit like pickled eggs.

I eat UNREFRIGERATED, RAW eggs all the time without incident. you can store them on the counter at room temp for at least two weeks. mercola.com even recommends it. what's more, salmonella is not a death sentence. eat farm fresh, free range, organic, anti biotic free and pesticide free as much as possible.

you feel better now? the guy was simply asking a question, not questioning your beliefs.

the curing process kills the microbes that would otherwise spoil the egg, that's why the egg can last as the name suggests a hundred years and still be edible. as long as you don't mind something that smells of rotten eggs, it takes a lot to attempt to eat one and is an aquired taste (not to mention texture) so they are safe to eat, but if they'll stay down, that depends on the person eating them. they were invented as a way to preserve eggs through the winter months back when there were no green houses pumping out fresh fruit all year round or imports from africa and south america in the corner shop less than a week after being picked. so it was an emergency solution that evolved into a delacacy

who cares about poison

I am not sure about the the germs issues, but I ate it from child till now, not cooked. But will cook with pork Congee most.

Hi Mike, great tutorial. Just wondering about the last step. If the goal is to keep oxygen out, can I just vacuum seal the eggs instead of the cling wrap and clay? Thanks!

1 reply

Probably, but if your bags don't seal or are punctured you risk spoiling your eggs. If you try it I'd love to see your results!