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Salt is a mineral composed primarily of
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
(NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantities in seawater. The open ocean has about of solids per liter of sea water, a
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
of 3.5%. Salt is essential for life in general, and saltiness is one of the basic human tastes. Salt is one of the oldest and most ubiquitous food
seasoning Seasoning is the process of supplementing food via herbs, spices, salts, and/or sugar, intended to enhance a particular flavour. General meaning Seasonings include herbs and spices, which are themselves frequently referred to as "seasonings". Ho ...
s, and is known to uniformly improve the taste perception of food, including otherwise unpalatable food. Salting, brining, and pickling are also ancient and important methods of
food preservation Food preservation includes processes that make food more resistant to microorganism growth and slow the oxidation of fats. This slows down the decomposition and rancidification process. Food preservation may also include processes that inhibit ...
. Some of the earliest evidence of salt processing dates to around 6,000 BC, when people living in the area of present-day Romania boiled spring water to extract salts; a salt-works in China dates to approximately the same period. Salt was also prized by the ancient Hebrews, Greeks, Romans, Byzantines, Hittites,
Egyptians Egyptians ( arz, المَصرِيُون, translit=al-Maṣriyyūn, ; arz, المَصرِيِين, translit=al-Maṣriyyīn, ; cop, ⲣⲉⲙⲛ̀ⲭⲏⲙⲓ, remenkhēmi) are an ethnic group native to the Nile, Nile Valley in Egypt. Egyptian ...
, and
Indians Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...
. Salt became an important article of trade and was transported by boat across the Mediterranean Sea, along specially built salt roads, and across the
Sahara , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...
on camel caravans. The scarcity and universal need for salt have led nations to go to war over it and use it to raise tax revenues. Salt is used in religious ceremonies and has other cultural and traditional significance. Salt is processed from salt mines, and by the
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
of seawater ( sea salt) and mineral-rich spring water in shallow pools. Its major industrial products are caustic soda and chlorine; salt is used in many industrial processes including the manufacture of polyvinyl chloride, plastics, paper pulp and many other products. Of the annual global production of around two hundred million tonnes of salt, about 6% is used for human consumption. Other uses include water conditioning processes, de-icing highways, and agricultural use. Edible salt is sold in forms such as sea salt and table salt which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency. As well as its use in cooking and at the table, salt is present in many processed foods. Sodium is an
essential nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
for human health via its role as an
electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...
and osmotic solute. Excessive salt consumption may increase the risk of cardiovascular diseases, such as
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
, in children and adults. Such health effects of salt have long been studied. Accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods. The World Health Organization recommends that adults consume less than 2,000 mg of sodium, equivalent to 5 grams of salt per day.


History

All through history, the availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC. Even the name Solnitsata means "salt works". While people have used
canning Canning is a method of food preservation in which food is processed and sealed in an airtight container (jars like Mason jars, and steel and tin cans). Canning provides a shelf life that typically ranges from one to five years, although u ...
and artificial refrigeration to preserve food for the last hundred years or so, salt has been the best-known food preservative, especially for meat, for many thousands of years. A very ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a salt spring in Lunca, Neamț County, Romania. Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract the salt as far back as 6050 BC. The salt extracted from this operation may have had a direct correlation to the rapid growth of this society's population soon after its initial production began. The harvest of salt from the surface of Xiechi Lake near Yuncheng in
Shanxi Shanxi (; ; formerly romanised as Shansi) is a landlocked province of the People's Republic of China and is part of the North China region. The capital and largest city of the province is Taiyuan, while its next most populated prefecture-lev ...
, China, dates back to at least 6000 BC, making it one of the oldest verifiable saltworks. There is more salt in animal tissues, such as meat, blood, and milk, than in plant tissues. Nomads who subsist on their flocks and herds do not eat salt with their food, but agriculturalists, feeding mainly on cereals and vegetable matter, need to supplement their diet with salt. With the spread of civilization, salt became one of the world's main trading commodities. It was of high value to the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and other peoples of antiquity. In the Middle East, salt was used to ceremonially seal an agreement, and the ancient Hebrews made a "
covenant of salt The phrase covenant of salt appears twice in the Hebrew Bible: In the Book of Numbers, God's covenant with the Aaronic priesthood is said to be a covenant of salt. In the second book of Chronicles, God's covenant with the Davidic kings of Israel ...
" with God and sprinkled salt on their offerings to show their trust in him. An ancient practice in time of war was salting the earth: scattering salt around in a defeated city to prevent plant growth. The Bible tells the story of King Abimelech who was ordered by God to do this at Shechem, and various texts claim that the Roman general Scipio Aemilianus Africanus ploughed over and sowed the city of Carthage with salt after it was defeated in the Third Punic War (146 BC). Salt may have been used for barter in connection with the
obsidian Obsidian () is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter elements s ...
trade in Anatolia in the Neolithic Era. Salt was included among funeral offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds, and salt fish. From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar, glass, and the dye Tyrian purple; the Phoenicians traded Egyptian salted fish and salt from North Africa throughout their Mediterranean trade empire. Herodotus described salt trading routes across Libya back in the 5th century BC. In the early years of the Roman Empire, roads were built for the transportation of salt from the salt imported at
Ostia Ostia may refer to: Places *Ostia (Rome), a municipio (also called ''Ostia Lido'' or ''Lido di Ostia'') of Rome *Ostia Antica, a township and port of ancient Rome *Ostia Antica (district), a district of the commune of Rome Arts and entertainment ...
to the capital. In Africa, salt was used as currency south of the Sahara, and slabs of rock salt were used as coins in Abyssinia. The Tuareg have traditionally maintained routes across the
Sahara , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...
especially for the transportation of salt by Azalai (salt caravans). The caravans still cross the desert from southern Niger to Bilma, although much of the trade now takes place by truck. Each camel takes two bales of
fodder Fodder (), also called provender (), is any agriculture, agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, domestic rabbit, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food g ...
and two of trade goods northwards and returns laden with salt pillars and dates. In Gabon, before the arrival of Europeans, the coast people carried on a remunerative trade with those of the interior by the medium of sea salt. This was gradually displaced by the salt that Europeans brought in sacks, so that the coast natives lost their previous profits; as of the late 1950s, sea salt was still the currency best appreciated in the interior. Salzburg, Hallstatt, and Hallein lie within of each other on the river Salzach in central Austria in an area with extensive salt deposits. Salzach literally means "salt river" and Salzburg "salt castle", both taking their names from the German word meaning salt. Hallstatt was the site of the world's first salt mine. The town gave its name to the
Hallstatt culture The Hallstatt culture was the predominant Western Europe, Western and Central European Archaeological culture, culture of Late Bronze Age Europe, Bronze Age (Hallstatt A, Hallstatt B) from the 12th to 8th centuries BC and Early Iron Age Europe ...
that began mining for salt in the area in about 800 BC. Around 400 BC, the townsfolk, who had previously used pickaxes and shovels, began open pan salt making. During the first millennium BC, Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries. The word '' salary'' comes from the Latin word for salt. The reason for this is unknown; a persistent modern claim that the Roman Legions were sometimes paid in salt is baseless. The word ''salad'' literally means "salted", and comes from the ancient Roman practice of salting leaf vegetables. Wars have been fought over salt.
Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto Regions of Italy, region. It is built on a group of 118 small islands that are separated by canals and linked by over 400  ...
fought and won a war with Genoa over the product, and it played an important part in the American Revolution. Cities on overland trade routes grew rich by levying duties, and towns like Liverpool flourished on the export of salt extracted from the salt mines of
Cheshire Cheshire ( ) is a ceremonial and historic county in North West England, bordered by Wales to the west, Merseyside and Greater Manchester to the north, Derbyshire to the east, and Staffordshire and Shropshire to the south. Cheshire's county t ...
. Various governments have at different times imposed salt taxes on their peoples. The voyages of Christopher Columbus are said to have been financed from salt production in southern Spain, and the oppressive salt tax in France was one of the causes of the French Revolution. After being repealed, this tax was reimposed by
Napoleon Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader who ...
when he became emperor to pay for his foreign wars, and was not finally abolished until 1946. In 1930, Mahatma Gandhi led a crowd of 100,000 protestors on the "Dandi March" or "
Salt Satyagraha The Salt March, also known as the Salt Satyagraha, Dandi March and the Dandi Satyagraha, was an act of nonviolent civil disobedience in colonial India led by Mahatma Gandhi. The twenty-four day march lasted from 12 March to 6 April 1930 as a di ...
", during which they made their own salt from the sea as a demonstration of their opposition to the colonial salt tax. This act of
civil disobedience Civil disobedience is the active, professed refusal of a citizen to obey certain laws, demands, orders or commands of a government (or any other authority). By some definitions, civil disobedience has to be nonviolent to be called "civil". Hen ...
inspired numerous Indians and transformed the Indian independence movement from an elitist one with little popular support into a national struggle.


Chemistry

Salt is mostly
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
(NaCl). Sea salt and mined salt may contain trace elements. Mined salt is often refined. Salt crystals are translucent and cubic in shape; they normally appear white but impurities may give them a blue or purple tinge. When dissolved in water sodium chloride separates into Na+ and Cl ions, and the solubility is 359 grams per litre. From cold solutions, salt crystallises as the dihydrate NaCl·2H2O. Solutions of sodium chloride have very different properties from those of pure water; the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...
of saturated salt solution is around 108.7 °C (227.7 °F).


Edible salt

Salt is essential to the health of humans and other animals, and it is one of the five basic taste sensations. Salt is used in many cuisines, and it is often found in salt shakers on diners' eating tables for their personal use on food. Salt is also an ingredient in many manufactured foodstuffs. Table salt is a refined salt containing about 97 to 99 percent
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
. Usually,
anticaking agents An anticaking agent is an additive placed in powdered or granulated materials, such as table salt or confectioneries, to prevent the formation of lumps ( caking) and for easing packaging, transport, flowability, and consumption. Caking mechani ...
such as sodium aluminosilicate or
magnesium carbonate Magnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals. Forms The most common magnesium carbonate forms are ...
are added to make it free-flowing. Iodized salt, containing potassium iodide, is widely available. Some people put a
desiccant A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant. Commonly encountered pre-packaged desiccants are solids that absorb water. Desiccant ...
, such as a few grains of uncooked rice or a saltine cracker, in their salt shakers to absorb extra moisture and help break up salt clumps that may otherwise form.


Fortified table salt

Some table salt sold for consumption contains additives that address a variety of health concerns, especially in the developing world. The identities and amounts of additives vary from country to country.
Iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...
is an important micronutrient for humans, and a deficiency of the element can cause lowered production of thyroxine (
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone. It can cause a number of symptoms, such as po ...
) and enlargement of the thyroid gland ( endemic goitre) in adults or cretinism in children. Iodized salt has been used to correct these conditions since 1924 and consists of table salt mixed with a minute amount of potassium iodide, sodium iodide, or sodium iodate. A small amount of
dextrose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
may also be added to stabilize the iodine. Iodine deficiency affects about two billion people around the world and is the leading preventable cause of mental retardation. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used. The amount of iodine and the specific iodine compound added to salt varies. In the United States, the Food and Drug Administration (FDA) recommends 150 micrograms of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), whereas in the UK the recommended iodine content of iodized salt is 10–22 ppm. Sodium ferrocyanide, also known as yellow prussiate of soda, is sometimes added to salt as an
anticaking agent An anticaking agent is an additive placed in powdered or granulated materials, such as table salt or confectioneries, to prevent the formation of lumps (caking) and for easing packaging, transport, flowability, and consumption. Caking mechanisms d ...
. Such anticaking agents have been added since at least 1911 when
magnesium carbonate Magnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals. Forms The most common magnesium carbonate forms are ...
was first added to salt to make it flow more freely. The safety of sodium ferrocyanide as a food additive was found to be provisionally acceptable by the Committee on Toxicity in 1988.Discussions of the safety of sodium hexaferrocyanate in table salt
. Hansard.millbanksystems.com (5 May 1993). Retrieved 7 July 2011.
Other anticaking agents sometimes used include tricalcium phosphate, calcium or magnesium carbonates, fatty acid salts ( acid salts), magnesium oxide, silicon dioxide,
calcium silicate Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO·SiO2. It is also referred to by the shortened trade name Cal-Sil or Calsil. It occurs naturally as the mineral larnite. ...
, sodium aluminosilicate and calcium aluminosilicate. Both the European Union and the United States Food and Drug Administration permitted the use of aluminium in the latter two compounds. In "doubly fortified salt", both iodide and iron salts are added. The latter alleviates iron deficiency anaemia, which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is
ferrous fumarate Iron(II) fumarate, also known as ferrous fumarate, is the iron(II) salt of fumaric acid, occurring as a reddish-orange powder, used to supplement iron intake. It has the chemical formula . Pure ferrous fumarate has an iron content of 32.87%, the ...
. Another additive, especially important for
pregnant Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...
women, is folic acid (vitamin B9), which gives the table salt a yellow color. Folic acid helps prevent neural tube defects and anaemia, which affect young mothers, especially in developing countries. A lack of
fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...
in the diet is the cause of a greatly increased incidence of dental caries.
Fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...
salts can be added to table salt with the goal of reducing tooth decay, especially in countries that have not benefited from fluoridated toothpastes and fluoridated water. The practice is more common in some European countries where water fluoridation is not carried out. In France, 35% of the table salt sold contains added sodium fluoride.


Other kinds

Unrefined sea salt contains small amounts of magnesium and calcium halides and sulfates, traces of algal products, salt-resistant bacteria and sediment particles. The calcium and magnesium salts confer a faintly bitter overtone, and they make unrefined sea salt hygroscopic (i.e., it gradually absorbs moisture from air if stored uncovered). Algal products contribute a mildly "fishy" or "sea-air" odour, the latter from
organobromine compounds Organobromine compounds, also called organobromides, are organic compounds that contain carbon bonded to bromine. The most pervasive is the naturally produced bromomethane. One prominent application of synthetic organobromine compounds is the u ...
. Sediments, the proportion of which varies with the source, give the salt a dull grey appearance. Since taste and aroma compounds are often detectable by humans in minute concentrations, sea salt may have a more complex flavor than pure sodium chloride when sprinkled on top of food. When salt is added during cooking however, these flavors would likely be overwhelmed by those of the food ingredients. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough
iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...
salts to prevent iodine deficiency diseases. Salts have diverse mineralities depending on their source, giving each one a unique flavour. Fleur de sel, a natural sea salt from the surface of evaporating brine in salt pans, has a distinctive flavour varying with its source. In traditional
Korean cuisine Korean cuisine has evolved through centuries of social and political change. Originating from ancient agricultural and nomadic traditions in Korea and southern Manchuria, Korean cuisine reflects a complex interaction of the natural envi ...
, so-called " bamboo salt" is prepared by roasting salt in a bamboo container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and has been claimed to increase the anticlastogenic and
antimutagenic Antimutagens are the agents that interfere with the mutagenicity of a substance. The interference can be in the form of prevention of the transformation of a promutagenic compound into actual active mutagen, inactivation, or otherwise the preventio ...
properties of doenjang (a fermented bean paste). Kosher or kitchen salt has a larger grain size than table salt and is used in cooking. It can be useful for brining, bread or
pretzel A pretzel (), from German pronunciation, standard german: Breze(l) ( and French / Alsatian: ''Bretzel'') is a type of baked bread made from dough that is commonly shaped into a knot. The traditional pretzel shape is a distinctive symmetrical ...
making and as a scrubbing agent when combined with oil. Pickling salt is made of ultra-fine grains to speed dissolving to make
brine Brine is a high-concentration solution of salt (NaCl) in water (H2O). In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for br ...
.


Salt in food

Salt is present in most
food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...
s, but in naturally occurring foodstuffs such as meats, vegetables and fruit, it is present in very small quantities. It is often added to processed foods (such as canned foods and especially salted foods, pickled foods, and
snack food A snack is a small portion of food generally Eating, eaten between meals. Snacks come in a variety of forms including packaged snack foods and other processed foods, as well as items made from fresh ingredients at home. Traditionally, snack ...
s or other convenience foods), where it functions as both a preservative and a flavoring. Dairy salt is used in the preparation of butter and cheese products. As a flavoring, salt enhances the taste of other foods by suppressing the bitterness of those foods making them more palatable and relatively sweeter. Before the advent of electrically powered refrigeration, salting was one of the main methods of
food preservation Food preservation includes processes that make food more resistant to microorganism growth and slow the oxidation of fats. This slows down the decomposition and rancidification process. Food preservation may also include processes that inhibit ...
. Thus,
herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...
contains 67 mg sodium per 100 g, while kipper, its preserved form, contains 990 mg. Similarly, pork typically contains 63 mg while
bacon Bacon is a type of salt-cured pork made from various cuts, typically the belly or less fatty parts of the back. It is eaten as a side dish (particularly in breakfasts), used as a central ingredient (e.g., the bacon, lettuce, and tomato sand ...
contains 1,480 mg, and potatoes contain 7 mg but potato crisps 800 mg per 100 g. Salt is also used extensively in
cooking Cooking, cookery, or culinary arts is the art, science and craft of using heat to Outline of food preparation, prepare food for consumption. Cooking techniques and ingredients vary widely, from grilling food over an open fire to using electric ...
as a flavoring, and cooking techniques such as with salt crusts and brining. The main sources of salt in the Western diet, apart from direct use of sodium chloride, are bread and cereal products, meat products and milk and dairy products. In many East Asian cultures, salt is not traditionally used as a condiment. In its place, condiments such as
soy sauce Soy sauce (also called simply soy in American English and soya sauce in British English) is a liquid condiment of Chinese origin, traditionally made from a fermented paste of soybeans, roasted grain, brine, and '' Aspergillus oryzae'' or ''Asp ...
, fish sauce and
oyster sauce Oyster sauce describes a number of sauces made by cooking oysters. The most common in modern use is a viscous dark brown condiment made from oyster extracts,The Times, 22 January 1981; ''Cook Accidentally on purpose'' sugar, salt and water thick ...
tend to have a high sodium content and fill a similar role to table salt in western cultures. They are most often used for cooking rather than as table condiments.


Biology of salt taste

Human salt taste is detected by sodium taste receptors present in taste bud cells on the tongue. Human sensory taste testing studies have shown that proteolyzed forms of
epithelial sodium channel The epithelial sodium channel (ENaC), (also known as amiloride-sensitive sodium channel) is a membrane-bound ion channel that is selectively permeable to sodium ions (). It is assembled as a heterotrimer composed of three homologous subunits α ...
(ENaC) function as the human salt taste receptor.


Sodium consumption and health

Table salt is made up of just under 40% sodium by weight, so a 6g serving (1teaspoon) contains about 2,400mg of sodium. Sodium serves a vital purpose in the human body: via its role as an electrolyte, it helps nerves and muscles to function correctly, and it is one factor involved in the osmotic regulation of water content in body organs ( fluid balance). Most of the sodium in the Western diet comes from salt. The habitual salt intake in many Western countries is about 10 g per day, and it is higher than that in many countries in Eastern Europe and Asia. The high level of sodium in many processed foods has a major impact on the total amount consumed. In the United States, 75% of the sodium eaten comes from processed and restaurant foods, 11% from cooking and table use and the rest from what is found naturally in foodstuffs. Because consuming too much sodium increases risk of
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
s, health organizations generally recommend that people reduce their dietary intake of salt. High sodium intake is associated with a greater risk of
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
, total cardiovascular disease and
kidney disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease of a kidney. Nephritis is an inflammatory kidney disease and has several types according to the location of the inflammation. Inflammation can ...
. A reduction in sodium intake by 1,000 mg per day may reduce cardiovascular disease by about 30 percent. In adults and children with no acute illness, a decrease in the intake of sodium from the typical high levels reduces blood pressure. A low sodium diet results in a greater improvement in blood pressure in people with
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
. The World Health Organization recommends that adults should consume less than 2,000 mg of sodium (which is contained in 5g of salt) per day. Guidelines by the United States recommend that people with hypertension, African Americans, and middle-aged and older adults should limit consumption to no more than 1,500 mg of sodium per day and meet the potassium recommendation of 4,700 mg/day with a healthy diet of fruits and vegetables. While reduction of sodium intake to less than 2,300 mg per day is recommended by developed countries, one review recommended that sodium intake be reduced to at least 1,200 mg (contained in 3g of salt) per day, as a further reduction in salt intake the greater the fall in systolic blood pressure for all age groups and ethnicities. Another review indicated that there is inconsistent/insufficient evidence to conclude that reducing sodium intake to lower than 2,300 mg per day is either beneficial or harmful. Evidence shows a more complicated relationship between salt and cardiovascular disease. "Mortality caused by levels of salt the association between sodium consumption and cardiovascular disease or mortality is U-shaped, with increased risk at both high and low sodium intake." The findings showed that increased mortality from excessive salt intake was primarily associated with individuals with hypertension. The levels of increased mortality among those with restricted salt intake appeared to be similar regardless of blood pressure. This evidence shows that while those with hypertension should primarily focus on reducing sodium to recommended levels, all groups should seek to maintain a healthy level of sodium intake of between 4 and 5 grams (equivalent to 10-13 g salt) a day. One of the two most prominent dietary risks for disability in the world are diets high in sodium.


Non-dietary uses

Only about 6% of the salt manufactured in the world is used in food. Of the remainder, 12% is used in water conditioning processes, 8% goes for de-icing highways and 6% is used in agriculture. Sodium chloride is one of the largest volume inorganic raw materials. Its major chemical products are caustic soda and chlorine. These are used in the manufacture of PVC, paper pulp and many other inorganic and organic compounds. Salt is also used as a
flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
in the production of aluminium. For this purpose, a layer of melted salt floats on top of the molten metal and removes iron and other metal contaminants. It is also used in the manufacture of soaps and glycerine, where it is used to
saponify Saponification is a process of converting esters into soaps and alcohols by the action of aqueous alkali (for example, aqueous sodium hydroxide solutions). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon chains. ...
fats. As an emulsifier, salt is used in the manufacture of
synthetic rubber A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubbe ...
, and another use is in the firing of pottery, when salt added to the furnace vaporises before condensing onto the surface of the ceramic material, forming a strong glaze. When drilling through loose materials such as sand or gravel, salt may be added to the drilling fluid to provide a stable "wall" to prevent the hole collapsing. There are many other processes in which salt is involved. These include its use as a mordant in textile dying, to regenerate resins in water softening, for the
tanning Tanning may refer to: * Tanning (leather), treating animal skins to produce leather * Sun tanning, using the sun to darken pale skin ** Indoor tanning, the use of artificial light in place of the sun ** Sunless tanning, application of a stain or d ...
of hides, the preservation of meat and fish and the
canning Canning is a method of food preservation in which food is processed and sealed in an airtight container (jars like Mason jars, and steel and tin cans). Canning provides a shelf life that typically ranges from one to five years, although u ...
of meat and vegetables.


Production

Food-grade salt accounts for only a small part of salt production in
industrialized countries A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
(7% in Europe), although worldwide, food uses account for 17.5% of total production. In 2018, total world production of salt was 300 million tonnes, the top six producers being China (68 million), the United States (42 million), India (29 million), Germany (13 million), Canada (13 million) and Australia (12 million). The manufacture of salt is one of the oldest chemical industries. A major source of salt is seawater, which has a
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
of approximately 3.5%. This means that there are about of dissolved salts, predominantly sodium () and chloride () ions, per kilogram (2.2 lbs) of water. The world's oceans are a virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated. The evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. Salt evaporation ponds are filled from the ocean and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity. Elsewhere, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These sources are either
mined Mined may refer to: * Mined (text editor), a terminal-based text editor * Mining, the extraction of valuable geological materials from the Earth See also * Mind (disambiguation) * Mine (disambiguation) Mine, mines, miners or mining may refer ...
directly, producing rock salt, or are extracted by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, purification was achieved in shallow open pans that were heated to accelerate evaporation. Vacuum-based methods are also employed. The raw salt is refined by treatment with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then applied. Some salt is produced using the Alberger process, which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake. The Ayoreo, an indigenous group from the Paraguayan Chaco, obtain their salt from the ash produced by burning the timber of the Indian salt tree ('' Maytenus vitis-idaea'') and other trees. One of the largest
salt mining Salt mining extracts natural salt deposits from underground. The mined salt is usually in the form of halite (commonly known as rock salt), and extracted from evaporite formations. History Before the advent of the modern internal combustio ...
operations in the world is at the Khewra Salt Mine in Pakistan. The mine has nineteen storeys, eleven of which are underground, and of passages. The salt is dug out by the room and pillar method, where about half the material is left in place to support the upper levels. Extraction of Himalayan salt is expected to last 350 years at the present rate of extraction of around 385,000 tons per annum.


In religion

Salt has long held an important place in religion and culture. At the time of
Brahmanic The historical Vedic religion (also known as Vedicism, Vedism or ancient Hinduism and subsequently Brahmanism (also spelled as Brahminism)), constituted the religious ideas and practices among some Indo-Aryan peoples of northwest Indian Subco ...
sacrifices, in Hittite rituals and during festivals held by Semites and Greeks at the time of the
new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...
, salt was thrown into a fire where it produced crackling noises. The ancient Egyptians, Greeks and Romans invoked their gods with offerings of salt and water and some people think this to be the origin of Holy Water in the Christian faith. In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water. Salt is considered to be a very auspicious substance in Hinduism and is used in particular religious ceremonies like house-warmings and weddings. In Jainism, devotees lay an offering of raw rice with a pinch of salt before a deity to signify their devotion and salt is sprinkled on a person's cremated remains before the ashes are buried. Salt is believed to ward off evil spirits in Mahayana Buddhist tradition, and when returning home from a
funeral A funeral is a ceremony connected with the final disposition of a corpse, such as a burial or cremation, with the attendant observances. Funerary customs comprise the complex of beliefs and practices used by a culture to remember and respect th ...
, a pinch of salt is thrown over the left shoulder as this prevents evil spirits from entering the house. In Shinto, is used for ritual purification of locations and people ( harae, specifically shubatsu), and small piles of salt are placed in dishes by the entrance of establishments for the twofold purposes of warding off evil and attracting patrons. In the Hebrew Bible, there are thirty-five verses which mention salt. One of these mentions Lot's wife, who was turned into a pillar of salt when she looked back at the cities of
Sodom and Gomorrah Sodom and Gomorrah () were two legendary biblical cities destroyed by God for their wickedness. Their story parallels the Genesis flood narrative in its theme of God's anger provoked by man's sin (see Genesis 19:1–28). They are mentioned frequ ...
(
Genesis Genesis may refer to: Bible * Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind * Genesis creation narrative, the first several chapters of the Book o ...
19:26) as they were destroyed. When the judge Abimelech destroyed the city of Shechem, he is said to have " sown salt on it," probably as a curse on anyone who would re-inhabit it (Judges 9:45). The
Book of Job The Book of Job (; hbo, אִיּוֹב, ʾIyyōḇ), or simply Job, is a book found in the Ketuvim ("Writings") section of the Hebrew Bible (Tanakh), and is the first of the Poetic Books in the Old Testament of the Christian Bible. Scholars ar ...
contains the first mention of salt as a condiment. "Can that which is unsavoury be eaten without salt? or is there any taste in the white of an egg?" (Job 6:6). In the New Testament, six verses mention salt. In the
Sermon on the Mount The Sermon on the Mount (anglicized from the Matthean Vulgate Latin section title: ) is a collection of sayings attributed to Jesus of Nazareth found in the Gospel of Matthew (chapters 5, 6, and 7). that emphasizes his moral teachings. It is ...
, Jesus referred to his followers as the "
salt of the earth Salt of the earth may refer to: Literature * A metaphor that occurs in the Sermon on the Mount, part of a discourse on salt and light * ''Salt of the Earth'', a book by Pope Benedict XVI Film * ''Salt of the Earth'' (1954 film), an American dr ...
". The apostle Paul also encouraged Christians to "let your conversation be always full of grace, seasoned with salt" (Colossians 4:6). Salt is mandatory in the rite of the Tridentine Mass. s:Catholic Encyclopedia (1913)/Salt Salt is used in the third item (which includes an Exorcism) of the Celtic Consecration (''cf.'' Gallican Rite) that is employed in the consecration of a church. Salt may be added to the water "where it is customary" in the Roman Catholic rite of Holy water. In Judaism, it is recommended to have either a salty bread or to add salt to the bread if this bread is unsalted when doing
Kiddush Kiddush (; he, קידוש ), literally, "sanctification", is a blessing recited over wine or grape juice to sanctify the Shabbat and Jewish holidays. Additionally, the word refers to a small repast held on Shabbat or festival mornings after t ...
for
Shabbat Shabbat (, , or ; he, שַׁבָּת, Šabbāṯ, , ) or the Sabbath (), also called Shabbos (, ) by Ashkenazim, is Judaism's day of rest on the seventh day of the week—i.e., Saturday. On this day, religious Jews remember the biblical storie ...
. It is customary to spread some salt over the bread or to dip the bread in a little salt when passing the bread around the table after the Kiddush. To preserve the covenant between their people and God, Jews dip the
Sabbath In Abrahamic religions, the Sabbath () or Shabbat (from Hebrew ) is a day set aside for rest and worship. According to the Book of Exodus, the Sabbath is a day of rest on the seventh day, commanded by God to be kept as a holy day of rest, as G ...
bread in salt. In Wicca, salt is symbolic of the element Earth. It is also believed to cleanse an area of harmful or negative energies. A dish of salt and a dish of water are almost always present on an altar, and salt is used in a wide variety of rituals and ceremonies.


References


Books

* * * * * * * * {{Good article Food additives Sodium minerals Objects believed to protect from evil Food powders