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Salt

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Image:Tablesalt.jpg
Salt is mostly sodium chloride (NaCl). This salt shaker also contains grains of rice, which some use to prevent caking
Image:Image-Zigong Salt.jpg
Brine being boiled down to pure salt in Zigong, China

Salt is a dietary mineral essential for animal life, composed primarily of sodium chloride. Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodised salt. It is a crystalline solid, white, pale pink or light grey in color, normally obtained from sea water or rock deposits. Edible rock salts may be slightly greyish in color due to this mineral content.

Chloride and sodium ions, the two major components of salt, are necessary for the survival of all living creatures including humans. Some isolated cultures, such as the Yanomami in South America, have been found to consume little salt, possibly an adaptation originated in the predominantly vegetarian diet of human primate ancestors.[1] Salt is involved in regulating the water content (fluid balance) of the body. Salt flavor is one of the basic tastes. Salt cravings may be caused by trace mineral deficiencies as well as by a deficiency of sodium chloride itself.

Overconsumption of salt increases the risk of health problems, including high blood pressure (see Health effects below). In food preparation, salt is used as a preservative and as a seasoning.

Contents

History

Main article: History of salt

Human beings have enjoyed canning and artificial refrigeration for only a couple of centuries; for the countless millennia before then, salt provided the best-known preservative of food, especially meat.[2]

The harvest of salt from the surface of the salt lake Yuncheng in Shanxi dates back to at least 6000 B.C., making it one of the oldest verifiable saltworks.[3]:18–19

Salt was included among funereal offerings found in ancient Egyptian tombs from the third millennium B.C., as were salted birds and salt fish.[3]:38 About 2800 B.C., the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon Cedar, glass, and the dye Tyrian purple; the Phoenicians traded Egyptian salt fish and salt from North Africa throughout their Mediterranean trade empire.[3]:44

On the river Salzach in central Austria, within a radius of no more than 17 kilometres, lie Salzburg, Hallstatt, and Hallein. Salzach literally means "salt water" and Salzburg "salt city", both taking their names from the Germanic root for salt, salz; Hallstatt literally means "salt town" and Hallein "saltwork", taking their names from hal(l)-, a root for salt found in Celtic, Greek, and Egyptian. The root hal(l)- also gave us Gaul, the Roman exonym for the Celts. Hallstatt and Hallein in Austria, Halle and Schwäbisch Hall in Germany, Halych in Ukraine, and Galicia in Spain: this list of places named for Celtic saltworks is far from complete.[4][5][6]

Hallstatt gave its name to the Celtic archaeological culture that began mining for salt in the area in around 1300 B.C. Around 400 B.C., the Hallstatt Celts, who had heretofore mined for salt, began flushing the salt out of mines as brine and boiling off the excess water. During the first millennium B.C., Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries.[2]

At times, troops in the Roman army were even paid in salt, which is the origin of the words salary and, by way of French, soldier. The word salad literally means "salted," and comes from the ancient Roman practice of salting leaf vegetables.[7]

In religion

There are thirty-five verses which reference salt in the English translation of the Bible (King James Version), the earliest being the story of Lot's wife, who was turned into a pillar of salt when she disobediently looked back at the wicked cities of Sodom (Genesis 19:26). When King Abimelech destroyed the city of Shechem he is said to have "sowed salt on it;" a phrase expressing the completeness of its ruin. (Judges 9:45.) In the Sermon on the Mount, Jesus referred to his followers as the "salt of the earth". 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. 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 the native Japanese religion Shinto, salt is used for ritual purification of locations and people, such as in Sumo Wrestling.

In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.

Forms of salt

Unrefined salt

Main articles: Sea salt, Halite, and Fleur de sel

Different natural salts have different mineralities, giving each one a unique flavor. Fleur de sel, natural sea salt harvested by hand, has a unique flavor varying from region to region.

Some advocates for sea salt assert that unrefined sea salt is more healthy than refined salts.[8] However, completely raw sea salt is bitter due to magnesium and calcium compounds, and thus is rarely eaten. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases.[9]

Unrefined sea salts are also commonly used as ingredients in bathing additives[10] and cosmetic products. One example are bath salts, which uses sea salt as its main ingredient and combined with other ingredients used for its healing and therapeutic effects.

Refined salt

Salt mounds in Bolivia.
Salt mounds in Bolivia.

Refined salt, which is most widely used presently, is mainly sodium chloride. Food grade salt accounts for only a small part of salt production in industrialised countries (3% in Europe[11]) although world-wide, food uses account for 17.5% of salt production[12]. The majority is sold for industrial use. Salt has great commercial value, because it is a necessary ingredient in the manufacturing of many things. A few common examples include: the production of pulp and paper, setting dyes in textiles and fabrics, and the making of soaps and detergents.

The manufacture and use of salt is one of the oldest chemical industries.[13] Salt is also obtained by evaporation of sea water, usually in shallow basins warmed by sunlight;[14] salt so obtained was formerly called bay salt, and is now often called sea salt or solar salt. Today, most refined salt is prepared from rock salt: mineral deposits high in salt.[citation needed] These rock salt deposits were formed by the evaporation of ancient salt lakes.[15] These deposits may be mined conventionally or through the injection of water. Injected water dissolves the salt, and the brine solution can be pumped to the surface where the salt is collected.

After the raw salt is obtained, it is refined to purify it and improve its storage and handling characteristics. Purification usually involves recrystallization. In recrystallization, a brine solution is treated with chemicals that precipitate most impurities (largely magnesium and calcium salts).[16] Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried.

Single-serving salt packets.
Single-serving salt packets.

Since the 1950s it has been common to add a trace of sodium hexacyanoferrate(II) to the brine; this acts as an anticaking agent by promoting irregular crystals.[17] Other anticaking agents (and potassium iodide, for iodised salt) are generally added after crystallization.[citation needed] These agents are hygroscopic chemicals which absorb humidity, keeping the salt crystals from sticking together. Some anticaking agents used are tricalcium phosphate, calcium or magnesium carbonates, fatty acid salts (acid salts), magnesium oxide, silicon dioxide, calcium silicate, sodium alumino-silicate, and alumino-calcium silicate. Concerns have been raised regarding the possible toxic effects of aluminium in the latter two compounds[citation needed]; however, both the European Union and the United States Food and Drug Administration (FDA) permit their use.[18] The refined salt is then ready for packing and distribution.

Table salt

Table salt is refined salt, 99% sodium chloride.[19][20] It usually contains substances that make it free flowing (anticaking agents) such as sodium silicoaluminate or magnesium carbonate. It is common practice to put a few grains of uncooked rice or half a dry cracker (such as Saltine) in salt shakers to absorb extra moisture when anticaking agents are not enough.

Additives

See also: History of iodised salt

Iodized salt (BrE: iodised salt) is table salt mixed with a minute amount of potassium iodide, sodium iodide, or iodate. Iodized salt is used to help reduce the chance of iodine deficiency in humans. Iodine deficiency commonly leads to thyroid gland problems, specifically endemic goiter. Endemic goiter is a disease characterized by a swelling of the thyroid gland, usually resulting in a bulbous protrusion on the neck. While only tiny quantities of iodine are required in a diet to prevent goiter, the United States Food and Drug Administration recommends (21 CFR 101.9 (c)(8)(iv)) 150 micrograms of iodine per day for both men and women, and there are many places around the world where natural levels of iodine in the soil are low and the iodine is not taken up by vegetables.

Today, iodized salt is more common in the United States, Australia and New Zealand than in the United Kingdom. Table salt is also often iodized—a small amount of potassium iodide (in the US) or potassium iodate (in the EU) is added as an important dietary supplement. Table salt is mainly employed in cooking and as a table condiment. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used.[21] Iodine is important to prevent the insufficient production of thyroid hormones (hypothyroidism), which can cause goitre, cretinism in children, and myxedema in adults.

The amount of iodine and the specific iodine compound added to salt varies from country to country. In the United States, iodized salt contains 46-77 ppm, while in the UK the iodine content of iodized salt is recommended to be 10-22 ppm.[22]

In some European countries where drinking water fluoridation is not practiced, fluorinated table salt is available. In France, 35% of sold table salt contains either sodium fluoride or potassium fluoride.[23] Another additive, especially important for pregnant women, is Folic acid (Vitamin B9), which gives the table salt a yellow color.

In Canada, at least one brand (Windsor salt) contains invert sugar. The reason for this is unclear.

Salty condiments

In many East Asian cultures, salt is not traditionally used as a condiment.[24]However, condiments such as soy sauce, fish sauce and oyster sauce tend to have a high salt content and fill much the same role as a salt-providing table condiment that table salt serves in western cultures.

Health effects

Sodium is one of the primary electrolytes in the body. All four cationic electrolytes (sodium, potassium, magnesium, and calcium) are available in unrefined salt, as are other vital minerals needed for optimal bodily function. Too much or too little salt in the diet can lead to muscle cramps, dizziness, or even an electrolyte disturbance, which can cause severe, even fatal, neurological problems.[25] Drinking too much water, with insufficient salt intake, puts a person at risk of water intoxication (hyponatremia). Salt is even sometimes used as a health aid, such as in treatment of dysautonomia.[26]

People's risk for disease due to insufficient or excessive salt intake varies due to biochemical individuality. Some have asserted that while the risks of consuming too much salt are real, the risks have been exaggerated for most people, or that the studies done on the consumption of salt can be interpreted in many different ways.[27] [28]

Excess salt consumption has been linked to:

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