The most distinctive feature of fermented herring is its pervasive, unmistakable odor. People who have never eaten pickled herring often cover their noses because of its pungent odor, and the Swedish government reportedly forbids the opening of canned herring in residential areas. International flights are also not allowed to carry this canned herring, because changes in air pressure can rupture the can, with serious consequences. Its odor is 300 times that of natto.
Swedish canned herring (Surstromming) is the world's stinkiest food and is usually available in Sweden during the short summer (around August). Every year from April to June when the herring spawn, fishermen salvage hundreds of tons of herring to prepare the ingredients for pickled herring. The unique feature of pickled herring is the natural fermentation. To ensure that the herring doesn't spoil during the fermentation process, the producers always boil the freshly salvaged herring in heavily salted water over a warm fire, and then put it into cans and let it ferment naturally.
The process of pickling herring is said to have been passed down for nearly 300 years, and it was only to save money that fishermen came up with the idea of pickling herring by natural fermentation, which uses less salt. By mid-August, the herring in the cans become sticky and juicy, and the gas in the cans expands as the herring ferments and bulges the cans, signaling that the herring is cured and ready for market.
In Sweden, parties are held every year on the third Thursday of August specifically for herring tasting, when pickled herring is said to taste best. On warm, short summer nights, Swedes set up tables and chairs in their gardens and serve up a dish of herring to feast on, drink and sing. The herring is often eaten with potatoes, onions, sour cream or bland, tasteless pancakes, chewed or swallowed in large chunks. Of course, the strong taste of wine is also a herring party essential to the "throat".