Surströmming (pronounced [sʉ̌ːʂtrœmːɪŋ], Swedish "soured (Baltic) herring") is a staple of traditional northern Swedish cuisine and is fermented Baltic herring. The Baltic herring, known as strömming in Swedish, is smaller than the Atlantic herring, found in the North Sea, and traditionally the definition of strömming (Baltic herring) is herring fished in the brackish waters of the Baltic north of the Kalmar sound The herring used for surströmming are caught just prior to spawning. The fermentation starts from a lactic acid enzyme in the spine of the fish, and so the fermentation is by autolysis; together with bacteria, pungent smelling acids are formed in the fish such as propionic acid, butyric acid and acetic acid. Hydrogen sulphide is also produced.
The salt raises the osmotic pressure of the brine above the zone where bacteria responsible for rotting (decomposition of proteins) can thrive and prevents decomposition of fish proteins into oligopeptides and amino acids. Instead the osmotic conditions enable the Haloanaerobium bacteria to prosper and decompose the fish glycogen into organic acids, making it sour (acidic). Fermented fish is an old staple in European cuisines; for example the ancient Greeks and Romans made a famous sauce from fermented fish called garum.
At one time a Swedish Royal decree (förordning) that the producers had lobbied for at the end of the 1940s to prevent fish not properly fermented being sold, set sales of the current years' production in Sweden to begin no earlier than the third Thursday in August. The decree is no longer law, but the trade still abides by the date for the "premiere".
When opened, the contents release a strong and sometimes overwhelming odour; the dish is ordinarily eaten outdoors. According to a Japanese study, a newly opened can of surströmming has one of the most putrid food smells in the world, even more so than similarly fermented fish dishes such as the Korean Hongeohoe or Japanese Kusaya.
Myths and Jokes 
A common myth tells that the dish originated with Swedish sailors in the 16th century. The story goes that they only had half the amount of salt needed to keep their fish fresh, so it began to rot. The sailors came across some Finnish islanders and decided to con them by selling the rotten fish to them. The Finns bought it and the sailors went away. A year later the Swedish sailors returned to the island and the locals asked if they had more rotten fish. The sailors decided to try it themselves, liked it and made more.
Another, probably more historically accurate, explanation of the origins of this method of preservation is that it began long ago, when brining food was quite expensive due to the cost of salt. When fermentation was used, just enough salt was used to prevent the fish from rotting. The fish are marinaded in a strong brine solution that draws out the blood, which is replaced by a weaker brine and the fermentation is done in barrels prior to canning (nowadays made of plastic). The canning procedure, introduced in the 19th century, enabled the product to be marketed in shops and stored in the home, whereas at one time the final stage would have been storage in large wooden barrels and smaller one liter kegs. Canning also enabled the product to be marketed farther south in Sweden, for homesick northern Swedes, and to be introduced among the southern Swedes as a curiosity and party food, serving as a background to schnapps as other spicy herring preparations do.
Historically, other fatty fish such as salmon and whitefish have been fermented in a way not unlike surströmming; the original gravlax resembled surströmming, whereas nowadays the product is covered with a salt and sugar mixture that permeates the fish without fermentation occurring.
The herring are caught in April and May, when they are in prime condition and just about to spawn. Prior to spawning, the herring have not fattened. They are then put into a strong brine for about 20 hours which draws out the blood, the heads are removed and they are gutted and put into a weaker brine solution. The barrels are then placed in a temperature controlled room kept at 15 to 20 degrees Celsius. Canning takes place at the beginning of July and for five weeks thereafter. Ten days prior to the premiere the final product is distributed to wholesalers.
The fermentation of the fish depends on a lactic acid enzyme in the spine that is activated if the conditions are right (temperature and brine concentration). The low temperatures in Northern Sweden is one of the parameters that affects the character of the final product.
Fermentation continues in the can which causes the can to bulge noticeably. Prior to modern canning methods, surströmming was sold in wooden barrels, and was only consumed locally. As even the smallest one litre kegs could leak, surströmming was bought directly from the producers in small quantities for immediate consumption.
As long ago as the 16th century, surströmming was supplied as army rations in the 30 years war. Swedish soldiers who did not come from the area where this was staple food as well as foreign conscripts refused to eat it.
Half a year to a year later gases have built up sufficiently for the once flat tops of the cylindrical tins to bulge into a more rounded shape. These unusual containers of surströmming can be found today in supermarkets all over Sweden. However, certain airlines have banned the tins on their flights, considering the pressurized containers to be potentially dangerous. Species of Haloanaerobium bacteria are responsible for the in-can ripening. These bacteria produce carbon dioxide and a number of compounds that account for the unique odour: pungent (propionic acid), rotten-egg (hydrogen sulfide), rancid-butter (butyric acid), and vinegary (acetic acid).
Eating surströmming 
Surströmming is often eaten with a kind of bread known as tunnbröd ("thin bread"). This thin, either soft or crispy bread (not to be confused with crisp bread) comes in big square sheets when crisp or as rounds of almost a metre in diameter when soft.
The custom in Höga Kusten ("The High Coast"), the area of northern Sweden where this tradition originates from, is to make a sandwich, commonly known as a "surströmmingsklämma", using two pieces of the hard and crispy kind of tunnbröd with butter, boiled and sliced or mashed potatoes (often mandelpotatis or almond potatoes) topped with fillets of the fish together with finely diced onions.
In the southern part of Sweden, it is customary to use a variety of condiments such as diced onion, gräddfil (fat fermented milk/sour cream similar to smetana) or crème fraîche, chives and sometimes even tomato and chopped dill.
The surströmming sandwich is usually served with snaps and light beers like pilsener or lager. Other drinks of choice are svagdricka, (lit. "weak drink", a Swedish low alcoholic dark malt beverage brewed since the Middle Ages small beer slightly similar to porter), water or cold milk. However, exactly what to drink or not to drink to surströmming is highly disputed among connoisseurs. Some claim that cold milk is the right and only choice while others refer to svagdricka as the most traditional drink. Surströmming is usually served as the focus of a traditional festivity, a "surströmmingsskiva" (surströmming party).
Many people do not care for surströmming, and it is generally considered to be an acquired taste. It is a food which is subject to strong passions (as is lutefisk); occasionally people like the taste on first try.
On June 4, 2005, the first surströmming museum in the world was opened in Skeppsmalen, 30 km north of Örnsköldsvik, a town at the northern end of the High Coast.
In April 2006, several major airlines (such as Air France and British Airways) banned the fish citing that the pressurised cans of fish are potentially explosive. The sale of the fish was subsequently discontinued in Stockholm's international airport. Those who produce the fish have called the airlines' decision "culturally illiterate," claiming that it is a "myth that the tinned fish can explode."
Surströmming today contains higher levels of dioxins and PCBs than the permitted levels for fish in the EU; Sweden was granted exceptions to these rules from 2002 to 2011, and a renewal of the exceptions was then applied for. Producers have said that if the application is denied they will only be allowed to use herring less than 17 centimetres long, which contain lower levels, which will affect the availability of herring.
In the news 
In 1981, a German landlord evicted a tenant without notice after the tenant spread surströmming brine in the apartment building's staircase. When the landlord was taken to court, the court ruled that the termination was justified when the landlord's party demonstrated their case by opening a can inside the courtroom. The court concluded that it "had convinced itself that the disgusting smell of the fish brine far exceeded the degree that fellow-tenants in the building could be expected to tolerate."
See also 
- Devil's dung (also considered to have a highly noxious smell)
- Hákarl, Icelandic rotten shark
- Fesikh, Egyptian fermented fish
- They are about one third the size of North Sea herring (Swedish sill) that is adapted to salt water. UNEP (United Nations Environment Programme)
- "Horrible". QI. Series H. Episode 7. 29 October 2010. BBC. BBC One. http://www.comedy.co.uk/guide/tv/qi/episodes/8/7/.
- Ingeborg Borgenstierna och Thomas Larsson Festdagar - Från Vår fru till vår fru quoted by Nordiska Museet, Stockholm (Swedish)
- Excerpt from "Hakkou ha chikara nari," Takeo Koizumi, NHK Ningen Kouza 2002 ISBN 4-14-084183-4
- Kurlansky M. "Chapter 8. A Nordic Dream". Salt: A World History. London: Vintage Books. p. 138. ISBN 978-0-09-928199-3.
- Oskars Surströmming (Swedish)
- Ruben Madsen, surströmming producer
- Swedish fermented herring dish considered safety risk on airlines, fishupdate.com, 28 March 2006.
- McGee, Harold (2004). On Food and Cooking (Revised Edition). Scribner. ISBN 0-684-80001-2. p 236
- Bevanger, Lars (1 April 2006). "Airlines ban 'foul' Swedish fish". British Broadcasting Corporation. Retrieved 2007-09-24.
- "Surströmmingen är räddad". Västerbottens-kuriren. 8 April 2011. Retrieved 2011-09-06.
- Rechtsanwalt Frank - Georg Pfeifer. Störung des Mietgebrauchs durch Mieter
- Wolfgang Fassbender in Swiss newspaper Neue Zürcher Zeitung, August 2011
- Ringblom, Fredrik and Westerlund, Örjan (2009) En handbok surströmming Grenadine. ISBN 9789185329816. (Swedish)
|Wikimedia Commons has media related to: Surströmming|
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- Food For Louis at Youtube