Natural form

Whole century eggs still in their muddy clay coating, as sold at market.

Shows the egg in its unpeeled preserved state — the dark clay-ash exterior is the first thing a reader encounters.

Dairy & Eggs

Century Egg (皮蛋)

Alkaline-preserved duck or chicken egg with a dark jelly white and creamy green yolk.

Century egg is a duck, chicken, or quail egg preserved in an alkaline mix for weeks, transforming the white into a translucent dark-brown jelly and the yolk into a creamy, gray-green center. A Chinese delicacy, it is sliced over congee, tofu, or pickled ginger, adding a savory, sulfurous, umami punch. Its bold ammonia-tinged flavor is mellowed by serving with vinegar and ginger.

Century Egg (皮蛋, pí dàn — literally 'leather egg') is a preserved egg cured in an alkaline paste of quicklime, ash, salt, and clay. The name is a folk mistranslation; the original Chinese term refers to the parchment-like coating, not the egg's age. Originating in Hunan Province during the Ming Dynasty, the process exploits alkaline chemistry to transform the egg's proteins and fats over weeks to months, producing the characteristic translucent, jelly-like white and the firm yet creamy, green-gray yolk.

The ammoniacal and sulfurous compounds — hydrogen sulfide and ammonia released as cystine and cysteine break down under high pH — create the egg's assertive, savory personality. Quality eggs carry a faint floral note beneath the characteristic pungency; an overwhelmingly fishy or bitter flavor signals over-processing or poor-quality starting material. Century Egg occupies a dual identity in Chinese cooking: a delicacy (佳肴) at its best, a humble pantry staple when mass-produced.

Sourced from duck, chicken, or quail eggs, the preservation concentrates and transforms the original flavor into something entirely distinct. The high pH environment denatures the white into a dense, translucent gel while the yolk undergoes saponification, forming metallic sulfides that create the blue-green to gray coloration. This same chemistry produces the green ring around hard-boiled egg yolks, but prolonged alkaline exposure intensifies and concentrates it.

Measured in: piece
Storage: Pantry

Allergens

Egg

Types & varieties

Duck Egg Century Egg

Standard and most common; larger, richer flavor, preferred for eating out of hand or as a standalone appetizer

Chicken Egg Century Egg

Smaller and milder; quicker to process, often used in congee and sliced dishes where a subtler presence is desired

Quail Egg Century Egg

Tiny specialty item; eaten whole as a garnish or in small bites

The Chemistry of Transformation

The alkaline curing process is a controlled chemical reaction, not simple preservation. When the egg is sealed in the high-pH paste, hydroxyl ions penetrate the shell and raise the interior pH dramatically. Under these conditions, the egg white's proteins denature and re-fold into a dense, translucent gel — the jelly-like texture that contrasts so sharply with a cooked egg white. The yolk's lipids undergo saponification, forming metallic sulfides that create the blue-green to gray coloration and a firm outer ring around a paste-like center. Modern industrial production can accelerate this process to 10–15 days, but traditional clay-and-ash curing over weeks develops greater aromatic complexity and that elusive floral note.

Quality eggs smell faintly floral beneath the characteristic pungency; an overwhelming fishy or bitter odor indicates over-processing
The green-gray yolk color is a sign of proper alkaline transformation, not spoilage
Some traditional recipes add tea, star anise, or other aromatics to the coating paste for added complexity

Common uses

Sliced and served as a cold appetizer with light soy sauce, ginger, and scallion oilQuartered or halved as a congee or rice porridge toppingDiced into fried rice or noodle dishes for added richness and textural contrastMashed into dipping sauces for hot pot and fondueHalved in a bowl of plain congee with a drizzle of sesame oil — a classic comfort pairingPressed into cold tofu or used in summer salads and cold appetizer platesServed alongside pickled vegetables as a bar snack in Chinese restaurantsChopped into porky steamed dishes such as steamed spare ribs with fermented black beansSliced thin and used as a garnish for braised dishes to add depthServed as part of a Chinese cold appetizer platter (凉菜)

Tips & pitfalls

Select eggs with uniform dark brown-to-black coloring and no cracks; the white should be translucent amber when peeled
Avoid eggs with an overwhelmingly strong ammonia odor beyond the characteristic slight pungency — this signals spoilage
Store unopened eggs in a cool, dry pantry; once cracked, refrigerate and consume within a week
To serve: rinse off the coating under warm water, peel carefully, and rinse again to remove any residue
Do not assume longer processing is always better; industrial rapid-processing (10–15 days) can lack the nuance of a properly monitored traditional cure
Slice with a wet knife or dip the blade in hot water between cuts to prevent the jelly white from sticking and tearing
When adding to congee or porridge, fold in just before serving to preserve the contrast between the jelly white and creamy yolk
If the yolk is chalky or dry throughout, the egg was likely over-processed; a properly cured yolk has a distinct firm ring and paste-like center

Nutrition

143kcal

Energy

598 kJ · per 100 g

Where the calories come from

Protein 36%Carbs 2%Fat 62%

Protein

12.6g

25% DV

Carbs

0.7g

0% DV

Fat

9.5g

12% DV

Fiber

0% DV

Sugars

0.4g

of which

Sodium

142mg

6% DV

Notable micronutrients

Selenium56% DV

Vitamin B1237% DV

Riboflavin (B2)35% DV

Vitamin A18% DV

Phosphorus16% DV

Folate12% DV

Source · USDA FoodData Central · approx. Egg, whole, raw, fresh

View on FDC →

In the shops

Matched grocery products

Eggs
24 dz · Mercadona
€5.60
Cooked Eggs
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€2.20
Large Eggs
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€1.80
Large Eggs
12 dc · Mercadona
€3.20
Medium M Eggs
12 dc · Mercadona
€3.00
Free-Range Eggs
6 dc · Mercadona
€2.10

Good to know

Origin: Hunan Province, China, Ming Dynasty (circa 1368–1644)
Primary Egg Used: Duck egg; also chicken and quail
Processing Time: 2 weeks to 5 months (not 100 years — the name is a mistranslation)
Preservation Method: Coated in a paste of quicklime, ash, salt, and clay, then stored in airtight containers
Chemical Process: Alkaline hydrolysis transforms egg proteins, creating the dark jelly white and green-gray creamy yolk
Shelf Life: 1–2 years unopened in pantry; up to 4 weeks refrigerated once opened
Flavor Profile: Ammoniacal, sulfurous, savory, with a creamy, umami-rich yolk; quality eggs carry a faint floral note
Sodium Content: High; significant due to salt in the preservation paste

Substitutes

Soft-Boiled Egg with Soy Marinade — Does not replicate the alkaline chemistry or jelly texture but provides a similar savory, protein-rich addition to congee or rice
Pickled Quail Eggs — More accessible in most markets; offers a comparable appetizer role with vinegar tang instead of alkaline pungency
Haminados (Middle Eastern Preserved Egg) — Slow-cooked in olive oil and spices; shares the preserved, dense-yolk characteristic and works in similar savory contexts

Pairs with

Ginger Scallion Sesame Oil Light Soy Sauce Silken TofuCongee or Rice PorridgeChili Oil or Fresh ChiliesBok Choy or Gai Lan

Also called

皮蛋 · Preserved Egg · Pidan · Thousand-Year Egg