How to Make Century egg
Century eggs (皮蛋, pidan) are Chinese preserved eggs transformed through alkaline curing rather than fermentation. The white becomes amber and gelatinous while the yolk turns dark green-gray and creamy. Despite the name, they're ready in weeks to months, not centuries.
Category: Eggs · Method: Alkaline · Time: 3-12w · Difficulty: 3/5 · Yield: varies · Temp: 18-22°C
History
Legend credits their discovery to the Ming Dynasty when eggs were found preserved in slaked lime and ash. The alkaline environment denatures proteins without bacterial fermentation. Century eggs became a prized delicacy, appearing in congee, salads, and dim sum throughout China and Southeast Asia.
Ingredients
- 12 Duck eggs — Fresh, unwashed
- 2 tbsp Black tea — Strong brewed
- 3 tbsp Salt
- 4 oz Calcium oxide (quicklime) — Food grade
- 1 cup Wood ash — Hardwood, clean
- 2 cups Rice hulls — For coating
Equipment
- Large bucket or container
- Rubber gloves
- Safety goggles
- Mixing tools
- Sealed crock for curing
Instructions
Make alkaline paste
CRITICAL SAFETY WARNING: Quicklime (Calcium oxide) is highly caustic and reacts violently with water. This is an exothermic reaction that can reach boiling temperatures and cause severe chemical and thermal burns. ALWAYS wear chemical-resistant gloves, eye protection (goggles), and long sleeves. Use a heat-resistant ceramic or heavy-duty plastic container. SLOWLY add the quicklime to the brewed tea in small increments; NEVER pour liquid into a large pile of lime as it can 'spit' or erupt. Stir gently until the reaction subsides, then incorporate the salt and wood ash to form a thick, smooth paste.
Time: 45 min
Tip: Perform this step in a well-ventilated area to avoid inhaling dust or vapors.
Cure
Pack eggs carefully in a crock or airtight container. Seal and store in a cool, dark place (18-22°C) for 4-8 weeks. If the environment is cooler (below 15°C), the process may take up to 12 weeks.
Time: 4-12 weeks
Tip: Longer curing results in a firmer texture and more intense flavor. Test one egg at the 4-week mark to check progress.
Clean, Rest, and Store
Remove the coating by scraping and rinsing under cold water. IMPORTANT: Once cleaned, allow the unpeeled eggs to 'rest' in a ventilated area for 1-2 days. This allows the concentrated ammonia gases to dissipate and the pH to stabilize, significantly improving the flavor profile. After resting, eggs can be stored unpeeled in a cool place or peeled and refrigerated.
Time: 2 days
Tip: Rinsing thoroughly is essential to remove all caustic residue before cracking the shell.
Fermentation Timeline
- Week 1: Alkaline penetration — Lime begins penetrating shell. Chemical changes start.
- Week 2: Protein transformation — Whites firming. Yolks beginning to change.
- Week 3: Color developing — Whites becoming amber. Yolks darkening.
- Week 4-8: Full transformation — Characteristic colors and textures achieved.
Signs of Success & Spoilage
Good signs
- Translucent amber white
- Creamy green-gray yolk
- Pine branch patterns on white (prized)
- Clean, complex flavor
- Ammonia-like aroma (normal)
Warning signs
- Cracked shells
- Mold inside
- Runny whites
- Foul smell beyond normal ammonia
Troubleshooting
- White not firm
- Cause: Under-cured Solution: Cure longer. Check paste consistency.
- Too strong ammonia
- Cause: Over-cured Solution: Cure for less time. Air out before eating.
- Paste cracking
- Cause: Too dry Solution: Add more liquid to paste. Seal container better.
Storage
Unpeeled in cool place; peeled in refrigerator Keeps Months unpeeled; 2 weeks peeled and refrigerated. Keep paste coating until ready to use for longest storage.
Health Benefits
- High protein content
- Rich in Vitamin A and Vitamin D
- Source of Iron and Selenium
- Alkaline-denatured proteins are often easier to digest
- Contains essential fatty acids
Serving Suggestions
- Sliced over congee (classic)
- With pickled ginger
- In cold tofu dishes
- Pi dan shou rou (with pork)
- As dim sum
- In hot pot
Related Eggs Ferments
Other Alkaline Ferments
- Natto — Legumes & Soy
- Soybean oil cake — Legumes & Soy
- Hákarl — Fish & Seafood
- Dawa-dawa (African locust) — Nuts & Seeds
- Ogiri (melon seed) — Nuts & Seeds