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Century egg
Century eggs (Chinese: 皮蛋; pinyin: pídàn; Jyutping: pei4 daan2), also known as alkalized or preserved eggs, are a Chinese dish 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 processing method.
Through the process, the yolk becomes dark greenish-grey in color, with a creamy consistency and strong flavor due to the hydrogen sulfide and ammonia present, while the white becomes dark brown in color, with a translucent jelly-like appearance, a gelatinous texture, and salty and umami 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, producing a variety of smaller flavorful compounds.[citation needed]
Some eggs have patterns near the surface of the egg white likened to pine branches. These patterned eggs are regarded as having better quality than the normal century eggs and are called Songhua eggs (Chinese: 松花蛋), variously translated as pine flower eggs or pine-patterned eggs.[citation needed]
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.
The century egg is known to have been present in Chinese cuisine since at least the 17th century CE and its purported origins are the subject of several folk tales. In one such tale, a homeowner living in Hunan during the Ming Dynasty 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 (水哥, lit. water-brother), also from Hunan, leaving duck eggs in the garden of a woman by the name of Songmei (松妹, lit. 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".
Preserved eggs were called "Chaoszi" in the Ming Dynasty.[failed verification] The 17th-century writer Fang Yizhi's "Little Knowledge of Physics" (物理小識) states: "The eggs produced in Chizhou are salted with five kinds of tree ash. Buckwheat grain ash is mixed to make it yellow and white, and charcoal lime is added to make it green and tough".
The traditional method for producing century eggs developed through improvement of the aforementioned primitive process. Instead of using only 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 1.4 kg (3 lb) of tea in boiling water. A smooth paste is then formed by mixing 1.4 kg (3 lb) of calcium oxide (3.2 kg or 7 lb, if done in winter), 4.1 kg (9 lb) of sea salt, and 3.2 kg (7 lb) of ash from burned oak, before being added to the tea. 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 another, 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. The eggs are then ready for consumption.
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 of table salt, calcium hydroxide and sodium carbonate for 10 days, followed by several weeks of aging in an airtight container, can achieve a similar effect to the traditional method. This is because the chemical reaction needed to produce century eggs is accomplished by introducing hydroxide and sodium ions into the egg, regardless of the method used.
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Century egg
Century eggs (Chinese: 皮蛋; pinyin: pídàn; Jyutping: pei4 daan2), also known as alkalized or preserved eggs, are a Chinese dish 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 processing method.
Through the process, the yolk becomes dark greenish-grey in color, with a creamy consistency and strong flavor due to the hydrogen sulfide and ammonia present, while the white becomes dark brown in color, with a translucent jelly-like appearance, a gelatinous texture, and salty and umami 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, producing a variety of smaller flavorful compounds.[citation needed]
Some eggs have patterns near the surface of the egg white likened to pine branches. These patterned eggs are regarded as having better quality than the normal century eggs and are called Songhua eggs (Chinese: 松花蛋), variously translated as pine flower eggs or pine-patterned eggs.[citation needed]
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.
The century egg is known to have been present in Chinese cuisine since at least the 17th century CE and its purported origins are the subject of several folk tales. In one such tale, a homeowner living in Hunan during the Ming Dynasty 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 (水哥, lit. water-brother), also from Hunan, leaving duck eggs in the garden of a woman by the name of Songmei (松妹, lit. 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".
Preserved eggs were called "Chaoszi" in the Ming Dynasty.[failed verification] The 17th-century writer Fang Yizhi's "Little Knowledge of Physics" (物理小識) states: "The eggs produced in Chizhou are salted with five kinds of tree ash. Buckwheat grain ash is mixed to make it yellow and white, and charcoal lime is added to make it green and tough".
The traditional method for producing century eggs developed through improvement of the aforementioned primitive process. Instead of using only 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 1.4 kg (3 lb) of tea in boiling water. A smooth paste is then formed by mixing 1.4 kg (3 lb) of calcium oxide (3.2 kg or 7 lb, if done in winter), 4.1 kg (9 lb) of sea salt, and 3.2 kg (7 lb) of ash from burned oak, before being added to the tea. 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 another, 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. The eggs are then ready for consumption.
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 of table salt, calcium hydroxide and sodium carbonate for 10 days, followed by several weeks of aging in an airtight container, can achieve a similar effect to the traditional method. This is because the chemical reaction needed to produce century eggs is accomplished by introducing hydroxide and sodium ions into the egg, regardless of the method used.