Surströmming, or “fermented herring,” is produced along Sweden’s Höga Kusten (High Coast) on the Gulf of Bothnia.
The origins of this product are uncertain, but it may date back to the 16th century when Swedish sailors ran short of salt with which to preserve herring and had to ferment the fish instead, before selling it to Finnish sailors. Fermentation was certainly an important preservation method when salt was a very expensive raw material.
When herring are fished in the spring, their heads are removed and they are packed in brine in barrels for at least a month. Next, the herring are canned along with brine (though a weaker brine than the one used in the barrels) so that the fermentation process can continue.
Surströmming can be stored for over a year, and during this time the tins swell up and lose their shape because of the gas released by the fermentation. The tins should be opened outdoors because of the strong smell that is released.
Traditionally, surströmming is sold starting on the third Thursday in August, before having fully ripened. Until about ten years ago, its sale was regulated by national law.
Small family companies along the coast continue the traditional, artisanal production of surströmming but, in the past few decades, larger companies have started to produce it as well. Larger companies do not always respect the traditional preparation methods and may, for example, use vinegar. Moreover, food safetly laws in the European Union have made the production of traditional surströmming more difficult. Sweden is trying to safeguard this artisanal product.
Surströmming was historically one of most-served foods in the military and on ships. Today it is often eaten in a sandwich, the surströmmingsklämma, made with tunnbröd (a thin bread), butter or sour cream, and vegetables such as potatoes and onions. This sandwich is often accompanied by beer, liquor, or milk.