Salt used in the saltfish industry. State of the art

Summary

The aim of this project has been to show the state-of-the-art with respect to salt applied in the salt and clipfish industry. The project has been divided into four work packages; 1) screen regulations dealing with salt quality for domestic and international markets, 2) map out methods for analysis of salt, 3) show consequences of using used salt, and 4) show the consequences for the product using new versus used salt. In the Norwegian regulation, the level of iron and copper must not exceed 10 and 0.1 mg/kg salt, no discoloration, and it shall not contain foreign matter. The salt applied in the saltfish industry contains 97–98 % NaCl in addition to several minerals like Ca, Mg, Cu, and sulphates. After use, the composition of the salt changes. In detail, the level of minerals decreases, while the water and protein content increases. The composition of the salt influences the quality of the product. For instance, elevated levels of Ca and Mg involves a longer time for salt uptake, drying, and desalting. The observed changes of the salt are from experiments with one part salt and one part of fish. There are also other elements influencing the product quality and yield, such as use of frozen-thawed fish vs. fresh fish, temperature, time, storage time and pressure as a result of the height of the stack. Recently, some saltfish industry has introduced mechanical filtration technology of used salt. They experience no difference between new and purified salt in terms of salt uptake, drying time or yield.