Century Egg (Asian Delicacies)
Nutrition Information
| Nutrient / Component | Century Egg (Per 100 g) | Century Egg (1 Whole, 65 g) | Salted Duck Egg (1 Whole, 65 g) |
|---|---|---|---|
| Energy (Calories) | 160 kcal | 104.0 kcal | 120.3 kcal |
| Water | 68.4 g | 44.5 g | 45.1 g |
| Protein | 14.36 g | 9.33 g | 8.45 g |
| Total Fat | 10.76 g | 6.99 g | 9.23 g |
| — Monounsaturated Fat | 4.80 g | 3.12 g | 4.16 g |
| — Polyunsaturated Fat | 1.10 g | 0.72 g | 0.88 g |
| — Saturated Fat | 2.90 g | 1.89 g | 2.73 g |
| Cholesterol | 608 mg | 395.2 mg | 402.4 mg |
| Total Carbohydrates | 2.40 g | 1.56 g | 1.17 g |
| Dietary Fiber | 0.0 g | 0.0 g | 0.0 g |
| Total Sugars | 0.40 g | 0.26 g | 0.33 g |
| Sodium | 605 mg | 393.3 mg | 1,027.0 mg |
| Potassium | 215 mg | 139.8 mg | 114.4 mg |
| Phosphorus | 200 mg | 130.0 mg | 128.0 mg |
| Calcium | 63 mg | 41.0 mg | 48.1 mg |
| Magnesium | 13 mg | 8.5 mg | 9.1 mg |
| Iron | 3.30 mg | 2.15 mg | 1.82 mg |
| Zinc | 1.30 mg | 0.85 mg | 0.88 mg |
| Selenium | 31.0 µg | 20.2 µg | 22.8 µg |
| Vitamin A (RAE) | 165 µg | 107.3 µg | 123.5 µg |
| Vitamin D (D3) | 1.2 µg (48 IU) | 0.78 µg (31 IU) | 0.85 µg (34 IU) |
| Vitamin E (Alpha-Tocopherol) | 1.15 mg | 0.75 mg | 0.81 mg |
| Vitamin B12 | 3.80 µg | 2.47 µg | 2.21 µg |
| Riboflavin (B2) | 0.320 mg | 0.208 mg | 0.195 mg |
| Pantothenic Acid (B5) | 1.20 mg | 0.78 mg | 0.85 mg |
| Folate (B9) | 54.0 µg | 35.1 µg | 39.0 µg |
| Choline | 230.0 mg | 149.5 mg | 158.6 mg |
Description
Preserved duck eggs—predominantly century eggs (pidan) and salted duck eggs (xiandanyou)—are traditional Asian culinary delicacies perfected through centuries of biochemical food preservation. While both traditionally utilize raw duck eggs (Anas platyrhynchos domesticus), their curing methods transform the internal macromolecular architecture into contrasting textures, umami profiles, and electrolyte densities. When analyzing preserved egg nutritional values per 100g, century eggs deliver approximately 160 calories, 14.4 grams of complete protein, and 10.8 grams of dietary lipids, while salted duck eggs supply 185 calories, 13.0 grams of protein, 14.2 grams of fats, and substantial electrolyte concentrations. For a standard dietary portion—commonly logged as one whole preserved egg (approx. 65 grams edible portion)—a century egg yields roughly 104 calories with moderate sodium, whereas a salted duck egg supplies 120 calories accompanied by a dense sodium profile.
Biochemical Transformation: Alkaline Curing vs. Brine Salting
The physiological and textural characteristics of these delicacies arise from fundamentally distinct biochemical processes:
Century Eggs (Alkaline Hydrolysis): Preserved in a clay-like matrix of wood ash, calcium oxide (quicklime), sodium carbonate, and black tea for several weeks to months, hydroxyl ions ($OH^-$) gradually diffuse through the semipermeable shell. This elevates the internal pH to 9–12, initiating alkaline denaturation of the albumin into a translucent, amber gel while breaking down proteins into savory amino acids and peptides. The yolk transforms into a dark green, creamy paste rich in sulfur and ammonia notes, accompanied by miniature dendrite crystals (known as pine needle or snowflake patterns) of insoluble magnesium ammonium phosphate.
Salted Duck Eggs (Osmotic Dehydration & Lipid Migration): Cured by packing in damp, salted charcoal paste or soaking in a saturated sodium chloride brine (~20–25% NaCl), osmotic pressure draws moisture out of the egg while sodium ions migrate inward. The salt destabilizes the low-density lipoprotein (LDL) spheres in the yolk, releasing bound triglycerides. This coalesces the yolk fats into a characteristic bright orange, granular, oil-dripping texture prized in mooncakes, pastries, and savory congee.
Macronutrient Density & Sodium Considerations
Both delicacies offer high-biological-value protein containing optimal ratios of all nine essential amino acids, with low total carbohydrates (~1.5–1.8g per egg). However, their mineral and electrolyte dynamics require careful dietary accounting:
Sodium Density in Salted Eggs: A single salted duck egg delivers over 1,000 mg of sodium (nearly 45% to 50% of the daily recommended limit), driven by prolonged brine diffusion. It functions as an intense seasoning element or savory condiment rather than a standalone high-volume protein source.
Century Egg Electrolyte Balance: Century eggs contain substantially less sodium (approx. 390 mg per egg), alongside elevated concentrations of trace minerals like calcium and iron resulting from alkaline compound penetration.
Lipid Integrity & Satiety: The rich yolks of both preserved eggs concentrate dietary phospholipids, lutein, and bioavailable Vitamin A, promoting strong gut peptide release (CCK and PYY) for lasting satiety.
