Salt

Foods, Other items

Availability: Earth

Chemical formula: NaCl (in commercial products it is never found in absolutely pure form, but always mixed with other constituents in variable proportions)

Chemical/physical properties:
Water solubility: 0.359 g mL⁻¹ at 20 °C

Introduction

Salt, primarily made up of sodium chloride (NaCl), is an essential mineral for life and one of the basic taste sensations. Long used both as a seasoning and a preservation method, salt enhances the flavor of food and allows it to be stored through techniques like salting and brining. It is a key ingredient in many cuisines and is commonly placed on the table in shakers, sometimes iodized to help prevent nutritional deficiencies.

Description of salt

Refined table salt contains about 97–99% sodium chloride and may include additives like anti-caking agents to maintain a smooth, free-flowing texture. Iodized salt, widely available since 1924, is enriched with potassium iodide or potassium iodate to help prevent iodine deficiency disorders, such as goiter and cretinism. The amount of iodine added varies by country and has played a major role in significantly reducing related diseases.

Some types of table salt are doubly fortified with iron to combat iron-deficiency anemia, which is common in developing countries, and may also contain folic acid to help prevent neural tube defects in pregnant women. Other additives, like sodium fluoride, are used to fight tooth decay, especially in areas lacking fluoridated water or toothpaste. Various substances are used to enhance salt’s properties, including calcium carbonate, magnesium carbonate, silicon dioxide, and aluminosilicates. These compounds improve flowability and product stability.

History of salt

Throughout history, the availability of salt has played a crucial role in the development of civilization. What is believed to be Europe’s first city, Solnitsata in Bulgaria, was actually a salt mine, supplying the region now known as the Balkans as early as 5400 BCE. For thousands of years, salt was the most reliable food preservative, especially for meat. An ancient saltworks operation was uncovered at the archaeological site of Poiana Slatinei, near a salt spring in Lunca, Romania. Evidence shows that the Neolithic people of the Precucuteni culture were boiling salt-rich spring water into salt cakes as early as 6050 BCE.

Salt is naturally more concentrated in animal source foods—such as meat, blood, and milk—than in plant source foods. As a result, nomadic peoples who live off livestock don’t need to supplement their diets with salt, while agricultural societies, whose diets are largely plant-based, must add salt to maintain health. As civilizations expanded, salt became one of the world’s most important trade commodities, highly prized by the Jews, Greeks, Romans, Byzantines, and many other ancient cultures.

In the Middle East, salt was used to seal ceremonial agreements. The ancient Hebrews, for instance, made a “covenant of salt” with God, sprinkling salt on their offerings to symbolize trust and loyalty. In warfare, salting the earth—as described in the story of King Abimelech and allegedly in Carthage by Scipio Aemilianus—was a symbolic act of destruction and curse.

In Africa, salt functioned as a form of currency south of the Sahara, with slabs of rock salt used as money in Abyssinia. The Tuareg people maintained salt trade routes across the desert, transporting goods via camel caravans. Overland salt trade, like that between coastal Gabon and the interior, illustrates salt’s economic and social significance. In Central Europe, towns such as Salzburg, Hallstatt, and Hallein, located along the Salzach River, thrived due to salt mining, giving rise to the Hallstatt culture.

Salt has even sparked wars, such as those between Venice and Genoa, and influenced major historical events, including the American Revolution. Salt taxes—in places like France and India—have triggered major uprisings, notably the Salt March led by Mahatma Gandhi in 1930, which turned the Indian independence movement into a national struggle.

Salt production method

Salt can be obtained from two main sources: seawater through natural evaporation, and terrestrial sedimentary deposits, often found in underground mines.

Extraction from seawater

Seawater, with an average salinity of around 3.5%, offers an inexhaustible supply of salt—so abundant that calculating its total reserves is unnecessary. In warm, dry coastal regions, natural evaporation is particularly efficient. Shallow ponds filled with ocean water gradually produce salt crystals as the water evaporates.

Extraction from terrestrial sedimentary deposits

Far from the sea, salt is extracted from sedimentary deposits left by the evaporation of ancient seas and lakes. Rock salt can be collected directly or dissolved in water and then recovered through the evaporation of brine. In traditional methods, purification took place in shallow open pans heated from below, while today more advanced systems are used, such as mechanical evaporation and the Alberger process. The latter produces salt with granular crystals, thanks to vacuum evaporation combined with the seeding of the solution. There are also artisanal methods, such as those of the Ayoreo people of Paraguay, who extract salt from the ashes of local wood.

Among the largest salt mines in the world stands out the Sifto mine, located 550 meters below Lake Huron in Canada, which produces about seven million tons of salt annually. Another emblematic example is the Khewra mine in Pakistan, famous for the “pink Himalayan salt“. This mine extends over 400 kilometers and uses the “room and pillar” method to ensure the stability of its structures. With an annual extraction rate of about 385,000 tons, its reserves are estimated to last for at least 350 years.

Classification of salt

Based on granule size, salt is classified as:

• Coarse salt (cooking salt)
• Table salt

Based on other characteristics, salt is classified as:

• Alaea salt
• Alpenbergkern salt
• Anatolian (Çankırı) salt
• Anglesey sea salt (Halen Môn)
• Asín tibuok
• Asin sa buy-o
• Bahamas sea salt
• Balinese sea salt
• Black lava salt
• Croatian sea salt
• Çamaltı (Billur) salt
• Dead Sea salt
• Egyptian frost salt
• Einville salt
• Fleur de sel
• Garam Bledug Kuwu
• Garam nipah
• Guerrero negro
• Himalayan salt
• Ilocano Asin
• Jukyeom
• Kalahari Salt
• Kala Namak
• Kampot sea salt
• Kanawha Valley salt
• Khoisan salt pearls
• Lake Grassmere salt
• Maldon Sea Salt
• Maras salt
• Mongolian lake salt
• Moshio salt
• Murray River salt flakes
• Namibian salt pearls
• Netarts Bay, Oregon salt
• Oriel Sea Salt
• Persian blue salt
• River reed salt
• Sale Marino di Trapani
• Sel gris
• Sel de Guérande
• Sal e Flor de Sal de Tavira DOP
• Sugpo Asin
• Tedted
• Tultul
• Utah salt
• Yellowstone salt

There are also flavored salts, including:

• Inca Fire Salt
• Sal de Gusano

Nutritional facts table

Nutrients	Per 100 g
Calories (kcal)	0
Total fat (g)	0
———Saturated fat (g)	0
Cholesterol (mg)	0
Sodium (mg)	39.300
Total carbohydrates (g)	0
———Dietary fiber (g)	0
———Total sugar (g)	0
Protein (g)	0