Surströmming (literally "sour herring") is an old, traditional Swedish preparation of fermented Baltic herring.

Fermenting process

Fermenting, an ancient method of preserving food, has been practised in many countries. There are several other fermented fish products known throughout the world, like the plara in Thailand, kusaya and funazushi in Japan, feseekh in Egypt, rakfisk in Norway, and súr hákarl in Iceland, among others.

The Swedish surströmming is made of the herring caught just before the spawning season, from late May to mid June. To start the fermentation process, the fresh, ungutted fish are first presalted for one to two days in salt brine. Then the fish are gutted by removing the head and guts, but leaving the roe, milt and a part of the intestine intact.

Placed in new salt brine, the fish are left to ferment for five to eight weeks in a controlled temperature. The process produces lactic acid preserving the fish, similarly to the development of sauerkraut.

In picture on right: a can of Swedish sour herring.

The lactic acid bacteria together with the enzymes in the fish are also responsible for producing the strong, foul smell of "rottenness" characteristic to the product, dreaded by many.

From the late July to the beginning of August, the surströmming is ready to be canned.

Sour herring premiere

Starting on the third Thursday of August, the Swedes celebrate a special surströmmingspremiär, sour herring premiere, similar to kräftskiva or kräftfest, the crayfish party. Surströmming enthusiast gather together to sample the year's sour herring products with all the proper trimmings. The feasts are usually organized outdoors because of the powerful smell emitted by the sour herring.

The can containing the sour herring must be opened carefully, since a considerable amount of pressure is built up inside it. The can should be tilted 45 degrees (as seen in the picture on right) and the lid punctured with a can opener at the highest point to release the gasses.

In picture on right: a tilted can of Swedish sour herring punctured with a can opener.

Some advise to do this by submerging the can in water in a sink or a basin, to prevent the opener being splattered by the smelly pickling liquid. However, the true sour herring connoisseurs are strictly against this.

After the can is opened, the herrings are filleted and the meat is eaten on top of buttered hard or soft Swedish flatbread (tunnbröd), together with sliced, freshly cooked almond potatoes, chopped onion and Swedish sour cream (gräddfil). Other toppings may include anything from tomato slices, sharp cheese or mysost to fresh dill, apple sauce, or even lingonberry jam. For accompanying beverages, water, ice-cold milk, schnaps and beer are recommended.

Confessions of a sour herring novice

Surströmming is also known in and imported to Finland, where it is called hapansilakka. In fact, some sources claim that the preparing of surströmming originated in Finland, although I doubt if we Finns very much care for taking the credit for this particular invention :-)

Nevertheless, the other day I planned to taste the dreaded dish, and below you will find a few notes about that not-so-happy event.

The opening of the can

After reading many an advice and tales of the mostly horrific encounters with sour herring, we decided to open the can in the balcony of our apartment.

After protecting my clothes and hair, dressed in an outfit my husband described as a homemade biohazard suit, I tilted the sour herring can as instructed above and punctured the lid with a can opener.

In picture on right: an opened can of Swedish sour herring.

A slight hissing sound was heard, as the pressure was released. No liquid was splattered out and only a faint sulphuric odour reached my face, so that wearing protective clothing was highly futile. "Was this it?", I wondered, while my husband was observing the procedure from the safety behind the shut glass door. But this was only the beginning, as I was soon to discover after opening the can thoroughly.

The smell

The pungent smell reminding of rotten eggs, sewage waste and garbage left to rot for days rapidly spread all over the balcony, attracting numerous flies and soon reached the inside of our apartment as well. Although I was prepared for the smell, the potency of it somewhat surprised me.

As the smell started to reach my husband's nostrils, he claimed to have a sudden flashback of being exposed to tear gas, of which he had a nasty experience while performing his mandatory military service. Needless to say, he absolutely refused to taste the fish :-)

The smell was not subdued until the sour herring container was taken out with the garbage and the whole apartment aired and sprayed with air freshener. I wonder how much longer would we have suffered of the smell if we had opened the can indoors.

The taste

As stated in many articles, the taste of sour herring, although being strong, is less vile than the smell. The flavour is rather pungent and acidic, but not overly so. Furthermore, if the herring is eaten on a flatbread with the traditional additives, the flavour is much diluted and masked by the other ingredients.

As a conclusion, I would say that I would be willing to eat sour herring again, as long as someone else opens the can at a considerable distance from the diners. However, claiming the sour herring to be as great a delicacy as the Nordic noble crayfish is a gross overstatement in my opinion.