Salmiak is the everyday Dutch, German and Nordic name for ammonium chloride (NH4Cl) when it is used in food. It is the reason Dutch zoute drop and Finnish salmiakki taste so different from the sweet licorice of Britain, Italy or the United States. Chemically it is a white, water-soluble salt; in the mouth it produces a sharp, slightly sour, drying sensation that people tend either to love or to find alarming.

Why is ammonium chloride in licorice? Because people like the taste. Salmiak began as a medicine — an expectorant in cough pastilles — and licorice was a cough remedy too. The two were combined in pastilles and, by the 1930s, salted licorice was being made commercially in the Netherlands and the Nordic countries. The flavour stuck.

The name

The word comes from Latin sal ammoniacum, "salt of Ammon", traditionally linked to the region of the temple of Amun in the Libyan desert. The older English name is sal ammoniac. Ammonium chloride has many non-food uses as well — in soldering, batteries and fertiliser — and in food it is authorised in the EU as the additive E 510.

From pharmacy to candy

Ammonium chloride was long used in medicine as an expectorant, and salmiak pastilles for coughs are still sold. Licorice root was likewise an old cough remedy. Exactly when and where the two were first combined as a sweet is not well documented, but by the 1930s salted licorice was being produced in Finland, Norway, Denmark, Sweden and the Netherlands. In the Netherlands it became the defining flavour of adult drop; the history of Dutch drop traces the wider story.

Why it tastes the way it does

Ammonium chloride is not simply "salty". A study published in Nature Communications in 2023 showed that it activates OTOP1, the proton channel taste cells use to detect sourness; mice lacking the channel no longer avoided strong ammonium chloride solutions. That helps explain why salmiak strikes newcomers as something between salty, sour and bitter, and why it is a taste usually learned in childhood.

How much is used

Amounts vary widely. Ingredient lists on Dutch packs show a couple of percent in ordinary salted drop (a Venco muntendrop pack lists 2.2%) and close to 10% in some double-salted products. In Sweden, popular salty licorice is reported to average about 7%. The often-repeated "7.99%" ceiling is a former German rule, not a Dutch one; see dubbelzoute. The health caution usually discussed for drop concerns glycyrrhizin from the licorice extract rather than the salmiak — see the chemistry of licorice.

The salmiak belt

Salted licorice is popular across a band of northern Europe: the Netherlands, northern Germany, Denmark, Sweden, Norway, Iceland and Finland. Finland takes salmiak further than anyone, with salmiak-flavoured ice cream and the salmiak vodka Salmiakki Koskenkorva. Elsewhere in the world it remains a curiosity, found mostly in specialist import shops.