nigari

Nigari, or magnesium chloride, is a by-product from the extraction of salt from sea water. It's made by letting seawater evaporate by exposing it to sunlight and heat. There are many ways to produce it, like letting it dry in the sun, kettle-boiling and reverse osmosis.

Nigari has a bitter taste, the name comes from the Japanese word Nigai for bitter. The bitterness is due to the precense of magnesium sulfate.