Century egg (‘pidan,’ also known as preserved egg and millennium egg) is a Chinese cuisine ingredient made by preserving fowl eggs in a mixture of clay, ash, salt, quicklime (calcium oxide), 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 gray color with a creamy consistency and an odor of sulfur and ammonia, while the white becomes a dark brown, translucent jelly with little flavor.
The transforming agent in the century egg is its alkaline material, which gradually raises the pH of the egg to around 9, 12, or more 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 fungal 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.’
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Century Egg
Pickling
Pickling, also known as ‘brining’ or ‘corning,’ is the process of preserving food with acid. Pickling began 4000 years ago using cucumbers native to India. It is called ‘achar’ in northern India. This was used as a way to preserve food for out-of-season use and for long journeys, especially by sea. Salt pork and salt beef were common staples for sailors before the days of steam engines. Although the process was invented to preserve foods, pickles are also made and eaten because people enjoy the resulting flavors.
Pickling may also improve the nutritional value of food by introducing B vitamins produced by bacteria (when pickled in a process utilizing fermentation). The term ‘pickle’ is derived from the Dutch word ‘pekel,’ meaning ‘brine’ (salt water). In the U.S. Canada, and Australia the word ‘pickle’ alone almost always refers to a pickled cucumber (other types of pickles will be described as ‘pickled onion,’ ‘pickled cauliflower,’ etc.), except when it is used figuratively. In the UK, ‘pickle’ refers to Ploughman’s pickle, a kind of chutney; a pickled cucumber is referred to as a ‘gherkin.’
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Fermentation
Fermentation [fur-men-tey-shuhn] is when a living cell uses sugar for energy without requiring oxygen. Yeast is an organism that ferments. When yeast ferments sugar, the yeast eats sugar and makes alcohol. Other organisms (such as bacteria) make vinegar (acetic acid) or lactic acid when they ferment sugar. Fermentation is used to make beer, some types of fuel, and to make bread rise. When yeast ferments, it breaks down the glucose into ethanol and carbon dioxide.
Ethanol fermentation always produces ethanol and carbon dioxide. It is important in bread-making, brewing, and winemaking. Lactic acid fermentation produces lactic acid. It happens in muscles of animals when they need lots of energy fast, and is also used to preserve foods in pickling. The word ‘fermentation’ is derived from the Latin verb ‘fervere,’ which means ‘to boil’ (same root as ‘effervescence’). It is thought to have been first used in the late fourteenth century in alchemy, but only in a broad sense. It was not used in the modern scientific sense until around 1600.
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