Salted and Century Eggs in Thai Cooking: A Visual and Sensory Guide

What Are Salted and Century Eggs in Thai Cooking?

In Thai cooking, salted eggs (called kai kem or khai khem) and century eggs (called khai yiao ma) are two distinct preserved egg products that add rich, savory depth to many dishes. Salted eggs are typically duck eggs cured in brine or packed in salted charcoal paste, resulting in a firm, bright orange-red yolk and a salty, slightly grainy texture. Century eggs are duck, chicken, or quail eggs preserved in an alkaline mixture of clay, ash, salt, quicklime, and rice hulls for weeks to months; they develop a translucent, dark brown jelly-like white and a creamy, dark greenish-gray yolk with a pungent, ammonia-like aroma. Both are recognizable by their intense colors and bold flavors, and they are used differently in Thai cuisine to provide contrast to fresh herbs, spicy sauces, and steamed rice.

How Are Thai Salted Eggs (Kai Kem) Made and Recognized?

Salted eggs are usually made with duck eggs because their larger yolks have a higher fat content, which gives the cured yolk a rich, oily texture. The traditional method involves soaking raw eggs in a saturated brine solution or coating them with a paste of salt and clay or ash. The salt draws out moisture and seasons the egg over 2–4 weeks. The result is a firm, bright orange-red yolk that is oily and granular, while the white becomes liquid and very salty. In Thai markets, salted eggs are sold raw or already hard-boiled; the raw ones must be cooked before eating. You can recognize them by their shell, which may be dyed pink or red, and by the intensely colored yolk when opened. The aroma is briny and slightly eggy, but not overpowering.

Using Salted Eggs in Thai Dishes

In Thai cuisine, salted egg yolks are prized for their rich, umami flavor and are often used as a topping or key ingredient. One of the most popular dishes is pla muk kai kem (squid stir-fried with salted egg yolk), where the yolk is mashed and fried until it forms a creamy, golden sauce that clings to the seafood. Salted egg yolks are also crumbled over salads like som tam (green papaya salad) or mixed into fried rice for bursts of saltiness. The salted egg white, being very salty, is usually used sparingly or discarded; it can be chopped and added to soups or omelets to replace some of the salt. Because salted eggs are shelf-stable after boiling, they are a convenient pantry item in Thailand.

Preparation Tips and Substitutes

To use raw salted duck eggs, simply boil them for about 10 minutes until hard, then peel and separate the yolk and white. If a recipe calls for only the yolk, you can reserve the white for another salty dish. If you cannot find Thai salted eggs, Chinese salted duck eggs are nearly identical and work perfectly. A quick substitute is to sprinkle a regular hard-boiled egg yolk with a little sea salt and let it sit for 10 minutes, but the texture will be less oily and the flavor less integrated, so the dish will lack the characteristic richness.

What Are Century Eggs (Khai Yiao Ma) and How Are They Made?

Century eggs, known in Thai as khai yiao ma, are made by preserving raw eggs in an alkaline mixture. Traditionally, duck eggs are coated with a paste of clay, ash, salt, quicklime, and rice hulls, then left to cure for several weeks to a few months. The alkaline environment changes the egg's proteins: the white transforms into a translucent, amber-brown jelly with a firm but springy texture, and the yolk becomes a creamy, dark green to gray paste with a strong, sulfurous, ammonia-like aroma. The flavor is rich, savory, and slightly pungent, often described as an acquired taste. Century eggs are usually eaten without further cooking; the shell is simply peeled away and the egg is sliced or cut into wedges.

Recognizing Century Eggs in Thai Cuisine

Century eggs are easily recognized by their dramatic appearance: the white is a shiny, dark brown jelly, and the yolk is a soft, dark greenish-gray center. The aroma is distinctive and can be strong, but when paired with sharp, fresh ingredients, it becomes more balanced. In Thailand, century eggs are often eaten as a snack or appetizer with pickled ginger, fresh chili, and a drizzle of sweet soy sauce or fish sauce. They are also added to khao tom (rice soup) or jok (congee), where the hot rice mellows the pungency and the creamy yolk enriches the broth. Unlike salted eggs, century eggs are not typically cooked in the dish; they are added at the end to retain their unique texture.

Handling and Serving Tips

To prepare a century egg, gently crack the shell and peel it under running water to remove any adhering coating. Rinse the egg and pat it dry. The jelly-like white can be cut with a knife, but it is easier to use a thread or wire to slice cleanly. Serve century eggs cold or at room temperature; heating them can intensify the ammonia smell. If the aroma is too strong, let the egg sit exposed to air for a few minutes or splash with a little vinegar or lime juice, which neutralizes some of the alkaline notes.

Comparing Salted Eggs and Century Eggs

The table below contrasts the key sensory and culinary attributes of these two preserved eggs to help you distinguish and use them correctly:

How Are Preserved Eggs Used in Thai Sauces and Condiments?

In Thai cooking, preserved eggs are often paired with bold sauces that cut through their richness or saltiness. Salted egg yolks are used to create a creamy sauce when sautéed with butter or oil, garlic, and sometimes curry paste; this sauce is tossed with seafood, chicken, or vegetables. Century eggs are commonly served with a dipping sauce made from fish sauce, lime juice, chopped shallots, fresh chilies, and a little sugar, which balances the egg's alkaline pungency. Sweet soy sauce and pickled ginger are also classic accompaniments. The key is to pair the intense preserved egg with something fresh, sour, or spicy to create a harmonious bite.

Simple Recipe: Thai Salted Egg Yolk Fried Rice

This quick dish showcases the rich flavor of salted egg yolks and is a great introduction to using preserved eggs in Thai cooking.

1. Cook 2 cups of jasmine rice and let it cool completely (day-old rice is best).
2. Hard-boil 2 salted duck eggs, peel, and separate the yolks from the whites. Mash the yolks with a fork; finely chop the whites.
3. In a wok or large skillet, heat 2 tablespoons of vegetable oil over medium heat. Add 2 minced garlic cloves and the mashed salted egg yolks. Stir-fry until the mixture becomes foamy and fragrant, about 1 minute.
4. Add the cooked rice and stir-fry, breaking up any clumps, until the rice is evenly coated with the yolk mixture and slightly crispy, about 3–4 minutes.
5. Add the chopped salted egg whites, 1 tablespoon of fish sauce, 1 teaspoon of sugar, and a pinch of white pepper. Toss well.
6. Serve hot, garnished with sliced cucumber, fresh cilantro, and a wedge of lime.

If you cannot find salted duck eggs, use 3 raw duck egg yolks cured in 1/2 cup salt for 24 hours; rinse, then boil or steam until firm before mashing. The flavor will be close but less complex.