Century egg - wikipedia Century egg Century Egg Alternative names preserved egg, hundred - year egg, thousand - year egg, thousand - year - old egg, millennium egg, black egg, blacking egg, skin egg Place of origin China Main ingredients Egg preserved in clay, ash, salt, quicklime, and rice hulls Variations duck, chicken or quail eggs Eggs Cookbook : Century Egg Media : Century Egg Century egg Chinese name Chinese 皮 蛋 Literal meaning leather / skin egg Transcriptions Standard Mandarin Hanyu Pinyin pídàn Yue : Cantonese Yale Romanization pèih dáan Jyutping pei4 daan2 Southern Min Hokkien POJ phî - tàn Alternative Chinese name Chinese 松 花 蛋 Literal meaning pine - patterned egg Transcriptions Standard Mandarin Hanyu Pinyin sōnghuādàn Yue : Cantonese Yale Romanization chùhng fā dáan Jyutping cung4 faa1 daan2 Southern Min Hokkien POJ chhái - tàn ( 彩蛋 ) hoe - nn̄g or he - nn̄g ( 灰 卵 ) Second alternative Chinese name Chinese 世 紀 蛋 Transcriptions Standard Mandarin Hanyu Pinyin shìjìdàn Vietnamese name Vietnamese trứng bách thảo Thai name Thai ไข่เยี่ยวม้า ( Khai Yiao Ma ) Japanese name Kanji 世紀 の 卵 Kana セイキ の たまご Transcriptions Romanization seiki no tamago Century egg or Pidan ( Chinese : 皮蛋 ; pinyin : pídàn ), also known as preserved egg, hundred - year egg, thousand - year egg, thousand - year - old egg, millennium egg, skin egg and black egg, is a Chinese preserved food product and delicacy made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, quicklime, 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 present, while the white becomes a dark brown, translucent jelly with a salty flavor. The transforming agent in the century egg is an alkaline 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 flavorful compounds. Some eggs have patterns near the surface of the egg white that are likened to pine branches, and that gives rise to one of its Chinese names, the pine - patterned egg. Contents 1 History 2 Methods 2.1 Traditional 2.2 Modern 3 Uses 4 Misconception and Etymology 5 Safety 6 See also 7 References 7.1 Bibliography History The method for creating century eggs likely came about through the need to preserve eggs in times of plenty by coating them in alkaline 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. According to some, the century egg has over five 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. Methods Century egg coated in a caustic mixture of mud and rice husk Traditional The traditional method for producing century eggs developed through improvement of the aforementioned primitive process. Instead of using just clay, a mixture of wood ash, calcium oxide, 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 three pounds of tea in boiling water. To the tea, three pounds of calcium oxide ( or seven pounds, if done in winter ), nine pounds of sea salt, and seven pounds 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 burns. It is then rolled in a mass of rice chaff, to keep the eggs from adhering to one and other, before the eggs are placed in cloth - covered jars or tightly woven baskets. The mud slowly dries and hardens into a crust over several months. Then the eggs are ready for consumption. Modern Century egg showing snow - flake / pine - branch ( 松花, sōnghuā ) patterns. These patterns are dendrites of various salts. Even though the traditional method is still widely practiced, modern understanding of the chemistry behind the formation of century eggs has led to many simplifications in the recipe. For instance, soaking raw eggs in a solution of table salt, calcium hydroxide, 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 reaction needed to produce century eggs is accomplished by introducing hydroxide and sodium ions into the egg, regardless of the method used. The extremely toxic compound lead ( II ) oxide speeds up the reactions which create century eggs, leading to its use by some unscrupulous producers. However, zinc oxide is now the recommended alternative. Although zinc is essential for life, excessive zinc consumption can lead to copper deficiency, so the finished product should have its zinc level assessed for safety. Uses Arranged century egg on a plate Century egg with congee Century eggs can be eaten without further preparation than peeling and rinsing them -- on their own, or as a side dish. As an hors d'œuvre, the Cantonese wrap chunks of this egg with slices of pickled ginger root ( 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, soy sauce, and sesame oil, in a style similar to Japanese hiyayakko. 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 omelet 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 '' ( Chinese : 皮蛋 瘦 肉 粥 ; pinyin : pídàn shòuròu zhōu ). 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 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 baby leeks, sliced abalone, pickled julienned carrots, pickled julienned daikon radish, seasoned julienned jellyfish, sliced pork, head cheese and the quartered century eggs is served. This is called a lahng - poon in Cantonese, which simply means `` cold dish ''. Misconception and etymology Century eggs for sale in Mainland China. According to a common misconception, century eggs are, or were once, prepared by soaking eggs in horse urine. The myth may have arisen from the urine - like odor of ammonia and other amines produced by the chemical reaction used to make century eggs. However, this myth is unfounded as horse urine has a pH ranging from 7.5 to 7.9 and therefore would not work for this process. In Thai and Lao, the common word for century egg translates to `` horse urine egg '', due to the distinctive urine - like odor of the delicacy : Thai : ไข่เยี่ยวม้า ( khàj jîaw máː ) ( RTGS : khai yiao ma ) Lao : ໄຂ່ຢ່ຽວມ້າ ( khāj jāw mâː ) Safety Heavy metals were used to speed up the process to turn more profit for less time and artificially increase the quality of the preserved egg. It was an unscrupulous practice in some small factories but it became rampant in China and forced many Taiwanese, Hong Kong, and other honest manufacturers to label their boxes `` Lead Free '' after the scandal went mainstream in 2013. Many production factories in China were using industrial quality copper sulphate which was contaminated with arsenic, lead, cadmium, and other heavy metals and toxic chemicals, to make eggs more translucent, lessen odor, provide smoother texture and encourage faster curing. The Chinese government has recently been trying to regulate food additives and license law abiding establishments to combat the food safety incidents in China posed by bad manufacturing practice. See also Food portal Shanghai portal China portal Balut ( egg ) Iron egg List of delicacies Pickled egg Salted duck egg Smoked egg Soy egg Tea egg Chinese red eggs Virgin boy egg References Wikimedia Commons has media related to Century egg. Wikibooks Cookbook has a recipe / module on century egg Jump up ^ Moskvitch, Katia ( 29 March 2013 ). `` Black eggs and ripe guava lead Taiwan 's tech revolution ''. BBC News. Retrieved 29 March 2013. Jump up ^ McGee, Harold ( 2004 ). On Food and Cooking : The Science and Lore of the Kitchen. Scribner. p. 117. ISBN 0 - 684 - 80001 - 2. ^ Jump up to : Hou, Xiangchuan ( 1981 ). `` Hunger and technology : Egg preservation in China ''. Food and Nutrition Bulletin. The United Nations University Press. 3 ( 2 ). ISBN 92 - 808 - 0254 - 2. Jump up ^ 益阳 市 政府 网 ( 2008 - 07 - 31 ). `` 益阳 名优 特产 : 松花 皮蛋 ''. Jump up ^ Chen, JrWei ; Su, HouPin ( 2004 ). `` A new process for preparing spots - free pidan ''. Journal of the Chinese Society of Animal Science. 33 ( 1 ) : 79 -- 88. Jump up ^ Billy. `` Three Emperor Egg ''. Atablefortwo.com.au. Retrieved 2012 - 05 - 24. Jump up ^ Helmenstine, Anne Marie. `` Are Century Eggs Soaked in Horse Urine ? '' About.com. Thursday 16 October 2008. Retrieved on 20 October 2009. Jump up ^ Wood, T. ; Weckman, T.J. ; Henry, P.A. ; Chang, S. - L. ; Blake, J.W. ; Tobin, T. ( 1990 ). `` Equine urine pH : Normal population distributions and methods of acidification ''. Equine Veterinary Journal. 22 ( 2 ) : 118 -- 21. doi : 10.1111 / j. 2042 - 3306.1990. tb04222. x. PMID 2318175. Jump up ^ Nuwer, Rachel. `` Unless You Like Toxic Chemicals, Skip This Chinese Delicacy ''. smithsonianmag.com. Retrieved 2 April 2018. Jump up ^ `` Preserved egg companies shut in toxic chemical scandal ''. scmp.com. Retrieved 2 April 2018. Bibliography Ho, Mabel ( 1988 ). Chemistry Potpourri : Unlocking Chemistry through Investigations. Singapore : Toppan. ISBN 978 - 981 - 00 - 0454 - 5. 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. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Century_egg&oldid=841466564 '' Categories : Food preservation Raw egg dishes Animal - based fermented foods Probiotic foods Chinese cuisine Hong Kong cuisine Macanese cuisine Tibetan cuisine Philippine cuisine Taiwanese cuisine Thai cuisine Christmas Island cuisine Hidden categories : All articles with dead external links Articles with dead external links from September 2011 Articles containing Chinese - language text Articles containing Vietnamese - language text Articles containing Thai - language text Articles containing Japanese - language text Articles containing simplified Chinese - language text Articles with specifically marked weasel - worded phrases from August 2016 Articles containing Lao - language text All articles with vague or ambiguous time Vague or ambiguous time from July 2017 Talk Contents About Wikipedia Bân - lâm - gú Беларуская Català Čeština Dansk Deutsch Español Français 한국어 Bahasa Indonesia Italiano עברית Lëtzebuergesch Lietuvių Magyar മലയാളം Nederlands 日本 語 Norsk Polski Português Русский Svenska ไทย Українська اردو Tiếng Việt 吴语 粵語 中文 22 more Edit links This page was last edited on 16 May 2018, at 01 : 27. 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Question: how do you make a 1000 year old egg
Answer: by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, quicklime, and rice hulls for several weeks to several months