People eat surströmming because, beneath its legendary stench, the fermented Baltic herring delivers a complex, intensely savory flavor that Swedes have prized for centuries. The smell is genuinely overpowering, dominated by hydrogen sulfide and butyric acid produced during months of bacterial fermentation. But the taste is something else entirely: salty, acidic, and deeply umami, especially when eaten the traditional way with accompaniments that balance and temper the intensity.
The Smell vs. the Taste
Most of surströmming’s notoriety comes from internet challenge videos where people open a can and immediately gag. That reaction is real. The fermentation process generates hydrogen sulfide (the compound behind the smell of rotten eggs), along with butyric acid and propionic acid, creating one of the most pungent food odors on earth. But smell and taste are different sensory experiences, and surströmming’s actual flavor profile is far more nuanced than the smell suggests.
The fish tastes intensely salty, sour, and savory. The flesh softens during fermentation into a tender, almost paste-like consistency, and the flavor carries a deep umami punch similar to aged cheese or fish sauce. Swedes who grew up eating it describe the taste as sharp and briny but balanced, nothing like what your nose would lead you to expect. The key is that almost nobody eats surströmming straight from the can. It’s always served with other ingredients that round out the experience.
How Fermentation Creates the Flavor
Surströmming is made from Baltic herring caught in spring, lightly brined (using far less salt than traditional preservation methods), and left to ferment in cans for several months. The low salt concentration allows halophilic bacteria, particularly species like Haloanaerobium praevalens along with Clostridiisalibacter and members of the Porphyromonadaceae family, to remain active inside the sealed can. These microbes break down the fish through their metabolic activity, producing organic acids like lactate, propionate, butyrate, and acetate, plus hydrogen sulfide.
At the same time, natural enzymes already present in the fish flesh and gut (including calpains and cathepsins) continue breaking down proteins. This combination of bacterial fermentation and enzymatic self-digestion is what gives surströmming its soft texture and concentrated flavor. It’s the same basic principle behind other fermented foods like kimchi, miso, or Roquefort cheese, just pushed to a more extreme point. The fermentation also continues after canning, which is why surströmming cans famously bulge outward from the pressure of gases building inside.
Cultural Tradition in Northern Sweden
Surströmming has roots going back centuries in northern Sweden, where it developed as a practical way to preserve fish when salt was expensive and scarce. Using less salt meant a cheaper product that could feed more people through long winters, even if the trade-off was a more pungent result. Over time, what started as economic necessity became a regional tradition and eventually a point of cultural pride.
The surströmming premiere, traditionally falling on the third Thursday of August, marks when the year’s new batch is considered ready to eat. In northern Swedish communities, this is a genuine social event. Families and friends gather outdoors (always outdoors) to share the meal together, often with beer or snaps. For many Swedes, eating surströmming is tied to childhood memories, family gatherings, and regional identity in much the same way that other cultures bond over their own acquired-taste delicacies.
The Traditional Way to Eat It
The proper serving method makes all the difference between a gag-inducing stunt and an actual meal. Surströmming is traditionally eaten on tunnbröd, a thin Swedish flatbread, layered with specific accompaniments designed to complement and soften the fish’s intensity. The classic combination includes boiled almond potatoes (a small, waxy Swedish variety), finely chopped raw onion, and sour cream or crème fraîche. Some people add butter, dill, or chives.
You take a piece of tunnbröd, spread it with butter or sour cream, add sliced potato and a small amount of the fermented herring, top it with onion, and roll it into a wrap. The starchy potato absorbs some of the saltiness, the sour cream adds fat and coolness, and the raw onion provides a sharp bite that cuts through the fermentation funk. Eaten this way, surströmming becomes one component in a balanced bite rather than an overwhelming solo experience. The portions of fish are small relative to everything else on the bread.
Opening the Can Safely
Because fermentation continues inside the sealed can, surströmming builds significant internal pressure. The bulging can is not a sign that something has gone wrong; it’s expected. But it does mean opening requires some care. The standard practice is to puncture or open the can while it’s submerged in a bucket of water. This serves two purposes: it prevents the pressurized brine from spraying outward, and it contains some of the initial burst of odor. Some people instead tap the can gently and angle it upward at about 45 degrees before opening to control the spray.
Opening should always happen outdoors and well away from where you plan to eat. The initial wave of smell when the can first opens is far stronger than the smell of the fish once it’s been rinsed and plated. Many people rinse the fillets briefly in water before serving to reduce the surface odor further.
Why the Smell Doesn’t Stop People
Plenty of beloved foods around the world smell terrible to outsiders. Durian is banned from hotels across Southeast Asia. Époisses cheese has been reportedly barred from public transport in France. Natto, the Japanese fermented soybean, repels many first-timers with its slimy texture and ammonia notes. Surströmming fits into this same category of foods where an initial sensory barrier gives way to a flavor that people genuinely enjoy and crave.
For Swedes who eat it regularly, the smell registers differently. Familiarity changes perception, and the context of a social gathering with good accompaniments reframes the experience entirely. There’s also an element of pride and fun in the ritual itself: the outdoor setting, the dramatic can opening, the reactions of newcomers trying it for the first time. Surströmming is as much a social event as it is a meal, and that shared experience is a big part of why it persists.
A Note on Baltic Herring and Contaminants
Baltic herring does carry higher levels of environmental contaminants, specifically dioxins and PCBs, than fish from cleaner waters. The European Union sets maximum contaminant levels for fish products, but Sweden and certain other Baltic states have a special exemption allowing them to sell fish that exceeds those EU limits domestically, as long as consumers are informed of the potential health risks. This means surströmming sold within Sweden may contain higher dioxin levels than would be permitted for export to other EU countries. For occasional consumption this is generally not a concern, but it’s worth knowing if you eat Baltic herring products regularly.