Surströmming: Sweden’s Fermented Herring and the World’s Most Notorious Preserved Fish

Let me be completely honest upfront: surströmming smells genuinely, impressively terrible. Not “pungent like blue cheese” terrible, or “acquired taste” terrible. The kind of terrible that gets cans banned from apartment buildings. Airlines have removed it from checked luggage. A Swedish school was briefly evacuated after someone opened a can. Scientific measurements of its volatile compounds have ranked it among the strongest food odors ever recorded — stronger than durian, hákarl, or Limburger cheese.

And yet. The Swedes have been making and eating it for at least 500 years, possibly longer. In northern Sweden — in the villages along the Gulf of Bothnia, in the fishing communities of Norrland, on the summer islands of the High Coast UNESCO World Heritage area — surströmming is not a dare food or a novelty. It is heritage. It tastes like childhood summers at the family cabin. It tastes like the food your grandfather ate at his grandfather’s table. Context, it turns out, matters profoundly to how we perceive flavor.

I tried surströmming for the first time at a traditional premiere party on the High Coast in August, organized by a Swedish journalist who grew up eating it. Following strict instruction — open the can outside, rinse the fish, eat immediately with all traditional accompaniments — my honest assessment was: it tasted considerably better than it smelled. The salt, the sour complexity, the rich fishiness softened by tunnbröd flatbread and sweet red onion and cold sour cream — it was genuinely good. Not something I’d eat every week. But a legitimate food with centuries of tradition behind it, not the prank it’s been made out to be on the internet.

500 Years of Baltic Herring: The History of Surströmming

The origin of surströmming is economic, not culinary. In 16th-century Sweden, the crown taxed salt heavily, making fully salt-preserved fish prohibitively expensive for the fishing communities of the far north. Traditional salt herring (saltströmming) required large salt quantities to fully preserve the fish; the fermented version that became surströmming used far less — enough to retard some bacterial growth without fully stopping fermentation, allowing the fish itself to preserve through enzymatic and bacterial breakdown rather than salt alone.

Early Swedish written records from the 1500s document fermented Baltic herring being traded in Norrland markets. Military provisioning records from the 17th century show soldiers being supplied with fermented herring on northern campaigns. What began as a solution to salt scarcity became, over generations, a cultural institution — particularly in the villages around the High Coast and the Ångermanälven river valley, where specific fishing families maintained distinct fermentation traditions passed from father to son.

The surströmmingspremiär — the surströmming premiere, held on the third Thursday of August each year — has roots in a 17th-century Swedish law mandating that fermented herring couldn’t be sold before a specific date, preventing underdeveloped product from reaching market. Though the law was repealed in 1998, the premiere tradition continues as one of the most distinctive seasonal food events in Scandinavia: Swedes gather at summer cabins and outdoor parties specifically to eat the new season’s catch, usually with considerable quantities of snaps and cold beer. The premiere is the cultural heart of surströmming, and experiencing it there — outside, in community, in summer — is the context that makes the food make sense.

How Surströmming Is Actually Made

The process begins each spring with the Baltic herring catch — specifically Clupea harengus membras, a subspecies smaller and fattier than Atlantic herring, caught just before spawning when the fish are at peak protein and fat content. The fish are cleaned (in traditional production, gills and entrails are removed while the roe is left; practices vary slightly between producers) and packed in wooden barrels with a carefully calibrated low-salt brine: approximately 6–8% salt concentration, compared to the 15–20% used in regular salt-preserved herring.

This is the critical variable. At low salt concentration, naturally occurring halophilic (salt-loving) bacteria — primarily species of Haloanaerobium and related genera — survive and begin breaking down the fish alongside native proteolytic and lipolytic enzymes. The fermentation is a combined enzymatic and bacterial process: enzymes break down muscle proteins and fats while bacteria produce organic acids and volatile flavor compounds. After several months in temperature-controlled conditions, the softened, partially fermented fish is canned — while still actively fermenting.

Unlike most canned foods, surströmming is not heat-sterilized after canning. The bacteria remain alive inside the sealed can, producing carbon dioxide as fermentation continues, causing the characteristic bulging that every surströmming can displays. The cans are released for the August premiere after roughly 6 months of total fermentation. At point of consumption, the fish has a softened, almost spreadable texture from enzymatic protein breakdown, an intense sour-salty-umami flavor profile, and the famous aroma — a complex mixture of hydrogen sulfide, butyric acid, propionic acid, and various other volatile compounds that has been measured as one of the most challenging food smells on earth.

The Nutritional Picture Nobody Talks About

All coverage of surströmming focuses on the smell. Very little focuses on the nutrition, which is genuinely excellent. Baltic herring is a cold-water oily fish rich in long-chain omega-3 fatty acids (EPA and DHA), vitamin D, vitamin B12, selenium, and high-quality complete protein. Fermentation doesn’t destroy these nutrients — it concentrates them as water is lost during enzymatic breakdown. The bioactive peptides created during protein breakdown have demonstrated antioxidant and anti-inflammatory properties in preliminary research on fermented fish products.

The probiotic picture is more complex than for lacto-fermented vegetables. The fermentation is primarily enzymatic and halophilic-bacterial in a high-salt environment, rather than the classic lactic acid fermentation of kimchi or sauerkraut. Specific probiotic health claims for surströmming are not well-established in the scientific literature. What is established is that it’s a minimally processed, traditionally fermented whole food with an exceptional nutrient density per serving. The sodium content is significant — it’s eaten in small amounts specifically because of its intensity — so it’s genuinely a condiment-scale food, not a primary protein source.

How to Eat Surströmming: The Part That Changes Everything

How you eat surströmming determines your entire experience of it. The traditional Swedish method was developed over centuries specifically to balance the intensity of the fish with complementary flavors and textures. Eating surströmming alone, plain from the can, indoors, is not how it’s meant to be eaten. It’s like eating pure vinegar and concluding that salad dressing is inedible.

The Traditional Assembly — Do This Exactly:

• Tunnbröd: Swedish soft flatbread — mild, slightly chewy, neutral in flavor. It wraps and softens everything. Available at Scandinavian food stores; Swedish-style rye crispbread (knäckebröd) also works in a different way. Potato flatbread is an acceptable substitute.
• Mandelpotatis or waxy boiled potatoes: Swedish almond potatoes are the traditional choice — small, waxy, with buttery flesh. Regular boiled waxy potatoes work perfectly. The starch is essential for balancing the salt-sour intensity of the fish.
• Thinly sliced red onion: Raw. The sharpness cuts through the richness.
• Crème fraîche or sour cream: Cooling, creamy, essential. It tames the intensity more than any other accompaniment.
• Fresh dill: Bright herbal note that lifts the whole assembly.
• Cold beer or aquavit: The traditional beverage. Both work; aquavit (particularly dill or fennel-flavored) is even better. Very cold beer is the more approachable choice for first-timers.

The Opening — Outdoors, Always:

Open the can outside, and open it at arm’s length, ideally with the top of the can slightly submerged in a bucket of water. The can is pressurized from internal gas production; brine will spray when you pierce it, and that brine is the most concentrated version of the aroma. Rinse the fish briefly under cold water to moderate intensity. Traditional premiere parties always involve someone dramatically opening cans to maximum outdoor audience reaction — part of the ritual.

The Assembly and Eating:

Place tunnbröd flat. Add a boiled potato. Lay one or two pieces of herring. Add red onion. Add crème fraîche. Add dill. Roll or fold and eat immediately. The combination transforms the experience: the fish’s intensity becomes savory depth embedded within cooling cream, starchy potato, sharp onion, and soft bread. The sum is genuinely good in a way the parts in isolation are not. This is not a food to analyze piece by piece. Eat it as assembled.

Where to Find Surströmming

Outside Sweden, surströmming is available from specialist Scandinavian food importers, online Swedish specialty food stores (several ship internationally), and IKEA Food stores have carried it periodically. The August premiere season is the best time to find freshly released cans — from that point, cans will continue aging slowly in storage. Older cans develop more complex, intense flavor as enzymatic processes continue.

Be aware that some export-market versions of “Swedish fermented herring” are milder, younger ferments targeted at international buyers. Authentic traditional surströmming has a noticeably bulging can, is produced in Sweden (check the label), and has an appropriately challenging smell upon opening. The real product from producers in Härnösand, Söråker, or the High Coast is worth specifically seeking out.

Troubleshooting the Experience

Can’t get past the smell to taste it

Solution: Rinse the herring under cold water — this moderates the volatile compounds significantly. Assemble immediately with all traditional accompaniments and take a complete bite (bread + potato + fish + onion + cream) rather than tasting the fish alone. Your olfactory cortex habituates rapidly — after the first complete bite, the smell diminishes psychologically because your brain starts associating it with flavor rather than alarm.

Fish is completely liquid or mush inside the can

Solution: This is normal for longer-fermented cans. Enzymatic breakdown continues in the sealed can; older cans will have much softer, sometimes nearly liquid fish. Mushy surströmming is perfectly edible — it just needs to be scooped rather than lifted in pieces. Some traditionalists prefer the more liquid, deeply fermented variety.

Can barely bulging / seems underdeveloped

Solution: Some production conditions reduce gas buildup. A lightly bulging can may indicate a younger ferment or specific canning conditions. Taste and smell will confirm whether fermentation has proceeded correctly. If it smells like surströmming, it is surströmming.

Flavor just tastes like salt with no complexity

Solution: You may have an export-market version with reduced fermentation. True traditional surströmming has pronounced sourness alongside the salt — the two are inseparable. If available, compare with a can from a different producer known for traditional production methods. Also consider that unopened cans stored in cool conditions continue to develop flavor over months.

The Broader Scandinavian Fermented Fish Tradition

Surströmming sits within a much larger Northern European tradition of fermenting fish that developed wherever salt was expensive and protein needed to be preserved through cold, dark winters. Norwegian rakfisk (fermented inland freshwater trout, typically from Lake Randsfjord) uses similar low-salt principles but different fish, different microorganisms, and produces a somewhat milder product typically eaten around Christmas. Icelandic hákarl uses alkaline decomposition of Greenland shark rather than salt brine — a different preservation chemistry entirely. Danish æbleskive is not fermented fish at all, but gravlax (cured salmon) sits at the less-fermented end of the same Scandinavian fish preservation spectrum.

Within surströmming itself, the High Coast producers (Höga Kusten) maintain traditional methods emphasizing longer fermentation times and smaller batch production. Industrial producers in Söråker have moved toward larger-scale, more controlled operations. Enthusiasts have strong opinions about which producers maintain authentic flavor profiles. The Swedish Surströmming Academy — yes, this exists — actively works to preserve production standards and cultural traditions around the food.

Frequently Asked Questions

What is surströmming?

Surströmming is traditional Swedish fermented Baltic herring, made by fermenting small herring in low-salt brine for approximately six months, then canning while still actively fermenting. It’s been produced in northern Sweden (Norrland) for at least 500 years. The fermented product is intensely pungent, salty, and sour, with deep umami character. It’s a genuine Swedish heritage food, not merely a novelty.

Why does surströmming smell so extreme?

The fermentation produces a complex mixture of volatile sulfur compounds (hydrogen sulfide), short-chain fatty acids (butyric, propionic, acetic), and protein breakdown products. Scientific measurements have ranked freshly opened surströmming among the most intense food aromas ever recorded. The smell is real, powerful, and genuinely challenging. The flavor, with proper accompaniments, is considerably more approachable than the smell suggests.

Is surströmming safe to eat?

Yes, properly fermented and commercially produced surströmming is safe. The combination of salt concentration and fermentation acids creates conditions hostile to pathogenic bacteria. Swedes have consumed it safely for five centuries. A severely dented can, visibly compromised seal, or unusual color beyond normal brown-gray fermented fish are reasons for caution — otherwise the product is safe.

Can I make surströmming at home?

Not practically, and not recommended. The process requires months of controlled temperature conditions, precise salt ratios, and conditions difficult to manage safely in home kitchens. Home fermented fish carries real risks if done incorrectly. Surströmming is one of the few traditional fermented foods in this series that genuinely should be sourced from experienced commercial producers rather than attempted at home.

What does surströmming taste like?

Eaten in the traditional way with all accompaniments: intensely savory and salty, powerfully umami-rich, with pronounced fermentation sourness, a soft almost-spreadable fish texture, and deep fishiness that integrates into the whole assembly rather than dominating it. The crème fraîche and boiled potato do significant work to moderate the intensity. Eaten plain, it’s overwhelming. Eaten traditionally, it makes sense.

How long does canned surströmming last?

Consumed within 1–2 years of canning, during which the fermentation and enzymatic breakdown continue slowly inside the sealed can. Older cans are more intensely flavored and softer in texture. Once opened, transfer any leftovers to an airtight container and refrigerate; consume within 1–2 days. The opened brine should go outdoors if possible.

One Meal Worth Having

Surströmming will probably never be your regular Tuesday dinner. That’s fine. But if fermented foods are your interest — and if you’re reading this, they are — there is real value in seeking it out at least once. Not as a dare, not as a viral challenge, but as a genuine encounter with one of Europe’s oldest and most distinctive food traditions.

The people who hate surströmming overwhelmingly ate it wrong: plain, indoors, in isolation, without context. The people who understand it ate it in the Swedish way: outside in August with cold beer and traditional accompaniments, surrounded by people who grew up with the smell. Food is always partly context. Surströmming makes this point more dramatically than almost anything else you will encounter.

Seek out a Scandinavian food importer. Buy two cans. Invite a curious friend. Open them outside. Make the traditional assembly. Then decide. You’ll have earned an opinion that actually means something.