Edible salt, also called table salt or just salt, is a mineral, one of a very few rocks commonly eaten by humans. There are different forms of edible salt: unrefined salt, refined salt, table salt or iodised salt. It is a crystalline solid, white, pale pink or light grey in colour, obtained from sea water or from rock deposits. Sea salt comes in fine or larger crystals. In nature, it includes not only sodium chloride, but also other vital trace minerals. Edible rock salts may be slightly greyish in colour due to this mineral content.
Salt is necessary for the survival of all living creatures, including humans. Salt is involved in regulating the water content (fluid balance) of the body. Salt flavour 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.
Salt is required for life, but overconsumption can increase the risk of health problems, including high blood pressure, in those individuals who are genetically predisposed to hypertension. In food preparation, salt is used as a preservative and as a seasoning.
Forms of edible salt
Unrefined salt
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 assert that unrefined sea salt is more healthy than refined salts. There are concerns, however, that raw sea or rock salts may not contain sufficient iodine salts to prevent iodine deficiency diseases like goitre.
Refined salt
Refined salt, that is most widely used presently, is mainly sodium chloride. Only about 7% of refined salt is used as a food additive. The majority is sold for industrial use, from manufacturing pulp and paper to setting dyes in textiles and fabric, to producing soaps and detergents, and has great commercial value.
The manufacture and use of salt is one of the oldest chemical industries. Salt is also obtained by evaporation of sea water, usually in shallow basins warmed by sunlight; 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 edible salt. These rock salt deposits were formed by the evaporation of ancient salt lakes. 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). Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried.
Anticaking agents (and potassium iodide, for iodised salt) are generally added at this point. 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, sodium alumino-silicate, and alumino-calcium silicate. Concerns have been raised regarding the possible toxic effects of aluminium in the latter two compounds, however both the European Union and the United States Food and Drug Administration (FDA) permit their use in regulated quantities. The refined salt is then ready for packing and distribution.
Table salt
Table salt is refined salt, nearly pure (95% or greater) sodium chloride. It usually contains substances that make it free flowing (anticaking agents) such as sodium silicoaluminate (common name is Tixolex), as well as a minute amount of invert sugar to prevent the salt from turning a yellow colour when exposed to sunlight, and to prevent a significant loss of iodine via vaporization. It is common practice to put a few grains of uncooked rice in salt shakers to absorb extra moisture when anticaking agents are not enough. Table salt is also often iodised—a small amount of potassium iodide is added as an important dietary supplement. Table salt is mainly employed in cooking and as a table condiment. Iodised table salt has significantly reduced disorders of iodine deficiency in countries where it is used. Iodine is important to prevent the insufficient production of thyroid hormones (hypothyroidism), which can cause goitre, cretinism in children, and myxedema in adults.
Table salt is now used all over the world.
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