Century eggs (), also known under a wide variety of names (see infobox), are a
Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of v ...
egg-based culinary dish made by preserving
duck,
chicken or
quail eggs in a mixture of
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
,
ash
Ash or ashes are the solid remnants of fires. Specifically, ''ash'' refers to all non-aqueous, non-gaseous residues that remain after something burns. In analytical chemistry, to analyse the mineral and metal content of chemical samples, ash ...
,
salt,
quicklime
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "''lime''" connotes calcium-containing inorganic ma ...
, and
rice hulls for several weeks to several months, depending on the method of processing.
Through the process, the
yolk becomes a dark green to grey color, with a creamy consistency and strong flavor due to the
hydrogen sulfide and
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
present, while the
white becomes a dark brown, translucent jelly with a salty flavor. The transforming agent in the century egg is an
alkaline
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of ...
salt, which gradually raises the
pH of the egg to around 9–12, during the curing process.
This chemical process breaks down some of the complex, flavorless proteins and fats, which produces a variety of smaller flavorsome compounds.
Some eggs have patterns near the surface of the egg white which are likened to
pine branches. These patterned eggs are regarded as having better quality than the normal century eggs and are called Songhua eggs (
Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of v ...
: ), variously translated as pine flower eggs or pine-patterned eggs. In 2014, tons of Songhua eggs were consumed in China.
History
The method for creating century eggs likely came about through the need to preserve eggs in times of plenty by coating them in
alkali
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of ...
ne clay, which is similar to methods of egg preservation in some Western cultures.
The clay hardens around the egg and results in the curing and creation of century eggs instead of spoiled eggs.
The century egg has at least four centuries of history behind its production. Its discovery, though not verifiable, was said to have occurred around 600 years ago in
Hunan during the
Ming Dynasty, when a homeowner discovered duck eggs in a shallow pool of
slaked lime that was used for mortar during construction of his home two months before. Upon tasting the eggs, he set out to produce more – this time with the addition of salt to improve their flavor – resulting in the present recipe of the century egg. An alternate story involves a young duck farmer by the name of ''Shuige'' (, water-brother), also from Hunan, leaving duck eggs in the garden of a woman by the name of ''Songmei'' (, pine-sister) as a courting gesture. The eggs were not discovered until the woman cleaned out the ash pit half a month later where they had turned into century eggs. In her honour, the farmer named the transformed eggs with their delicate crystalline patterns on their surfaces "pine-patterned eggs".
Methods
Traditional
The traditional method for producing century eggs developed through improvement of the aforementioned primitive process. Instead of using only
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
, a mixture of
wood ash
Wood ash is the powdery residue remaining after the combustion of wood, such as burning wood in a fireplace, bonfire, or an industrial power plant. It is largely composed of calcium compounds along with other non-combustible trace elements presen ...
,
calcium oxide
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "''lime''" connotes calcium-containing inorganic ...
, and
salt is included in the plastering mixture, thereby increasing its
pH and
sodium content. The addition of calcium oxide and wood ash to the mixture lowers the risk of spoilage and also increases the speed of the process. A recipe for creating century eggs starts with the infusion of of
tea
Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of ''Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of southwestern China and norther ...
in boiling water. To the tea, of
calcium oxide
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "''lime''" connotes calcium-containing inorganic ...
(, if done in winter), of
sea salt
Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea sal ...
, and of ash from burned
oak is mixed into a smooth paste. Each egg is individually covered by hand, with gloves worn to protect the skin from
chemical burn
A chemical burn occurs when living tissue is exposed to a corrosive substance (such as a strong acid, base or oxidizer) or a cytotoxic agent (such as mustard gas, lewisite or arsine). Chemical burns follow standard burn classification and may ca ...
s. It is then rolled in a mass of rice
chaff, to keep the eggs from adhering to one another, before the eggs are placed in cloth-covered
jar
A jar is a rigid, cylindrical or slightly conical container, typically made of glass, ceramic, or plastic, with a wide mouth or opening that can be closed with a lid, screw cap, lug cap, cork stopper, roll-on cap, crimp-on cap, press-on cap ...
s or tightly woven
basket
A basket is a container that is traditionally constructed from stiff fibers and can be made from a range of materials, including wood splints, runners, and cane. While most baskets are made from plant materials, other materials such as horsehai ...
s. The mud slowly dries and hardens into a crust over several months. The eggs are then ready for consumption.
Modern
Even though the traditional method is still widely practised, modern understanding of the chemistry behind the formation of century eggs has led to many simplifications in the recipe. Today, soaking raw eggs in a
solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Solutio ...
of
table salt,
calcium hydroxide
Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime ( calcium oxide) is mixed or slaked with water. It has m ...
and
sodium carbonate for 10 days, followed by several weeks of aging while wrapped in plastic, is said to achieve the same effect as the traditional method. This is because the chemical reaction needed to produce century eggs is accomplished by introducing
hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...
and
sodium ions into the egg, regardless of the method used.
The extremely toxic compound
lead(II) oxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula Pb O. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern a ...
speeds up the reactions which create century eggs, leading to its use by some unscrupulous producers,
[ whereas zinc oxide is now the recommended alternative. Although zinc is essential for life, excessive zinc consumption can lead to ]copper deficiency
Copper deficiency, or hypocupremia, is defined either as insufficient copper to meet the needs of the body, or as a serum copper level below the normal range. Symptoms may include fatigue, decreased red blood cells, early greying of the hair, an ...
, and the finished product should have its zinc level assessed for safety.
Uses
Century eggs can be eaten without further preparation other than peeling and rinsing them – on their own, or as a side dish. In central China, they are sliced into pieces and drizzled with some black vinegar
Black vinegar is dark-colored vinegar used in Chinese cuisine.
Types
China
One of the most important types of Chinese "black vinegar" is the Shanxi mature vinegar () from the central plains of Northern China, particularly in the Shanxi pro ...
and served as a side dish. As an '' hors d'œuvre'', the Cantonese wrap chunks of this egg with slices of pickled ginger root
Ginger (''Zingiber officinale'') is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice and a folk medicine. It is a herbaceous perennial which grows annual pseudostems (false stems made of the rolled bases of le ...
(sometimes sold on a stick as street food). A Shanghainese recipe mixes chopped century eggs with chilled tofu. In Taiwan, it is popular to eat sliced century eggs placed on top of cold tofu with ''katsuobushi
is simmered, smoked and fermented skipjack tuna (''Katsuwonus pelamis'', sometimes referred to as bonito). It is also known as bonito flakes. ''Katsuobushi'' or similarly prepared fish is also known as .
Shaved ''katsuobushi'' and dried ...
'', soy sauce, and sesame oil, in a style similar to Japanese ''hiyayakko
is a Japanese dish made with chilled tofu and toppings.
Variety of toppings
The choice of toppings on the tofu vary among households and restaurants, but a standard combination is chopped green onion with katsuobushi (dried skipjack tuna fl ...
''. A variation of this recipe common in northern China is to slice century eggs over chilled silken (soft) tofu, adding liberal quantities of shredded young ginger and chopped spring onions as a topping, and then drizzling light soy sauce and sesame oil over the dish, to taste. They are also used in a dish called old-and-fresh eggs, where chopped century eggs are combined with (or used to top) an omelette
In cuisine, an omelette (also spelled omelet) is a dish made from beaten eggs, fried with butter or oil in a frying pan (without stirring as in scrambled egg). It is quite common for the omelette to be folded around fillings such as chives, ...
made with fresh eggs. The century eggs may also be cut into chunks and stir fried with vegetables, which is most commonly found in Taiwanese cuisine.
Some Chinese households cut them up into small chunks and cook them with rice porridge to create "century egg and lean pork ''congee
Congee or conjee ( ) is a type of rice porridge or gruel eaten in Asian countries. It can be eaten plain, where it is typically served with side dishes, or it can be served with ingredients such as meat, fish, seasonings and flavourings, most ...
''" (). This is sometimes served in dim sum restaurants. Rice congee, lean pork, and century egg are the main ingredients. Peeled century eggs are cut into quarters or eighths and simmered with the seasoned marinated lean slivers of pork until both ingredients are cooked into the rice congee. Fried dough sticks known as ''youtiao
''Youtiao'' (), known in Southern China as Yu Char Kway is a long golden-brown deep-fried strip of dough of Chinese origin and (by a variety of other names) also popular in other East and Southeast Asian cuisines.
Conventionally, ''youtiao' ...
'' are commonly eaten with century egg congee. Another common variation of this dish is the addition of salted duck eggs into the congee mixture.
At special events like wedding banquets or birthday parties, a first course platter of sliced barbecued pork, pickled
Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called a ...
baby leeks, sliced abalone
Abalone ( or ; via Spanish , from Rumsen ''aulón'') is a common name for any of a group of small to very large marine gastropod molluscs in the family Haliotidae. Other common names are ear shells, sea ears, and, rarely, muttonfish or m ...
, pickled
Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called a ...
julienned
Julienne, , or french cut, is a culinary knife cut in which the food item is cut into long thin strips, similar to matchsticks. Common items to be julienned are carrots for , celery for , potatoes for julienne fries, or cucumbers for .
Trimmin ...
carrot
The carrot (''Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, ''Daucus carota'', nati ...
s, pickled julienned daikon radish
Daikon or mooli, '' Raphanus sativus'' var. ''longipinnatus,'' is a mild-flavored winter radish usually characterized by fast-growing leaves and a long, white, root. Originally native to continental East Asia, daikon is harvested and consume ...
, seasoned julienned jellyfish, sliced pork, head cheese
Head cheese ( Dutch: ''hoofdkaas'') or brawn is a cold cut terrine or meat jelly that originated in Europe. It is made with flesh from the head of a calf or pig (less commonly a sheep or cow), typically set in aspic, and usually eaten cold, ...
and the quartered century eggs is served. This is called a ''lahng-poon'' in Cantonese
Cantonese ( zh, t=廣東話, s=广东话, first=t, cy=Gwóngdūng wá) is a language within the Chinese (Sinitic) branch of the Sino-Tibetan languages originating from the city of Guangzhou (historically known as Canton) and its surrounding ar ...
, which simply means "cold dish".
Misconception and etymology
Century eggs are sometimes avoided due to the belief that they are prepared by soaking eggs in horse urine
Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra.
Cellular m ...
, but there is no valid evidence to support this. Also, urine is generally not alkaline. In Thai and Lao, the common word for century egg translates to "horse urine egg", due to the distinctive urine-like odor of the food:
* th, ( RTGS: ''khai yiao ma'')
* lo,
Safety
Century eggs prepared in traditional ways are generally safe to consume. However, there have been incidents of malpractice in century egg production that causes eggs to be contaminated. In 2013, three factories in Jiangxi province were found to be using industrial copper sulphate Copper sulfate may refer to:
* Copper(II) sulfate, CuSO4, a common compound used as a fungicide and herbicide
* Copper(I) sulfate
Copper(I) sulfate, also known as cuprous sulfate, is an inorganic compound with the chemical formula Cu2 SO4. I ...
in century egg production to shorten the production time. The industrial copper sulphate was contaminated with heavy metals and toxic chemicals. The incident was exposed on China's national broadcaster CCTV
Closed-circuit television (CCTV), also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly t ...
, causing local officials to shut down 30 factories for inspection. The police arrested three people involved in the case and seized four businesses involved in the case.
Gallery
Century egg1.jpg, Century egg coated in a caustic
Caustic most commonly refers to:
* Causticity, a property of various corrosive substances
** Sodium hydroxide, sometimes called ''caustic soda''
** Potassium hydroxide, sometimes called ''caustic potash''
** Calcium oxide, sometimes called ''caust ...
mixture of mud and rice husk
Century egg snow flake.jpg, Century egg showing snow-flake/pine-branch (, ''sōnghuā'') patterns. These patterns are dendrites of various salts.
Arranged century egg on a plate.jpg, Arranged century egg on a plate
CenturyEgg.JPG, Century egg with congee
Congee or conjee ( ) is a type of rice porridge or gruel eaten in Asian countries. It can be eaten plain, where it is typically served with side dishes, or it can be served with ingredients such as meat, fish, seasonings and flavourings, most ...
Century eggs for sale in Hong Kong by tracyhunter.jpg, Century eggs for sale in Hong Kong
Khai_nyiau_ma.jpg, Pink century eggs in Laos
See also
*
*
*
*
*
*
*
*
*
References
Citations
Sources
*
*Taiwan Livestock Research Institute and Philippine Council for Agriculture (2001
Enhancing the Value of Eggs: How to Make Balut and Century Eggs
Retrieved 24 March 2007.
External links
*
*
{{Eggs
Food preservation
Raw egg dishes
Chinese cuisine
Hong Kong cuisine
Macau cuisine
Tibetan cuisine
Philippine cuisine
Taiwanese cuisine
Thai cuisine
Christmas Island cuisine