What is salt?
Salt, or sodium chloride (NaCl), is a common mineral used in the manufacture of many products and as a food seasoning. Salt is the main mineral in sea water, making up three-quarters of the 3.5% of dissolved minerals in sea water. Salt also occurs naturally in mineral deposits, where it is known as rock salt. Because New Zealand has no rock salt deposits, salt was imported from the time of European arrival in the early 1800s until the country developed a sea-salt industry in the 1950s.
Almost 1% of human blood is salt. The salt-derived sodium in the blood helps regulate the body’s water balance, plays a central role in electrical impulses in the nerves, and assists cells to take up nutrients. Although some salt is vital to health, most people in the developed world eat too much of it.
Easy on the salt
Traditionally, New Zealanders sprinkle salt over a meal before even tasting it. This habit not only irks many chefs, it is unhealthy. Excess salt can cause health problems such as high blood pressure. On average, New Zealanders consume about 9 grams of sodium per day – the recommended amount is between 2.3 grams and 5.9 grams.
Salt is used to flavour food, and to preserve foods such as butter, meat and fish. During the 19th century it was added to soils as a fertiliser. It was also sprinkled onto hay during stacking so that livestock would get the benefit of sodium when the hay was fed out. Since the 20th century salt has been also been used in textile dyeing, bleaching paper, curing leather and in the dairy, food manufacturing and pharmaceutical industries.
Early salt-making attempts
Captain James Cook saw Polynesians in Hawaii manufacturing salt in the late 1700s, but it was never produced by Māori in New Zealand. Nevertheless, Māori had a conception of saltiness in their word mātaitai, meaning tasting of salt, or brackish. Their sodium needs were met through a diet of fish and shellfish. When salt was introduced by Europeans, some Māori believed that eating salted foods caused their people to contract illnesses previously unknown to them. However, the real reason was that Māori had no natural immunity to the infectious diseases introduced by Europeans.
In 1844 the Nelson Examiner reported that salt had been successfully evaporated from sea water in the local estuary. It seems the venture was carried out by a former whaling captain, who was unhappy about the price of imported Liverpool salt. In 1866 an import duty was imposed on salt in the hope that this would stimulate domestic production. It did not.
In 1892 the New Zealand government offered a bonus of £1 per ton on production of the first 500 tons (453 tonnes) of salt, provided it was done by 31 March 1893. The incentive prompted Aucklander John Stubbs to try his luck on the western side of Rangitoto Island, but the venture failed. In Gisborne in the early 1900s Francis de Latour tried pumping sea water onto towers of bundled sticks and strips of cloth that were exposed to the air. The method, which had been used in Japan, worked by using the large exposed surface area to increase the evaporation rate. However, it was not successful in New Zealand.
Iodine and salt
Before the 1920s many New Zealanders suffered from goitre, a swelling of the thyroid gland in the neck. It was the result of iodine deficiency, which can also cause mental disability in children. Because many New Zealand soils are iodine deficient, this trace element has been added to table salt since 1924 – a public health initiative which saw the virtual disappearance of goitre by the late 1950s.
Since the end of the 20th century specialty products such as flaky salt and coarse salt have become popular, but these lack iodine. A 1990s survey showed that many New Zealanders, especially children, were slightly iodine deficient. This was probably due to a decrease in salt intake and a move towards non-iodised salt by food manufacturers and consumers.