The reason why canned herring smells so bad is because in the process of making canned herring, only the head and guts are removed. After cleaning, it is soaked in salt water for a period of time, then cooked over medium-low heat, and then put into cans to ferment naturally for a few months. That's why only canned herring smells so bad, and according to experimental studies, canned herring tastes 300 times worse than natto. The reason why canned herring smells so bad is because of the unique way this food is made. All that is needed to produce canned herring is that the herring would be caught in the spring, the head and guts removed, cleaned, placed in salt water and boiled over medium-low heat. Next it would be canned for natural fermentation. After a few months of natural fermentation, it is ready to be put on the market for sale. Canned herring is one of the traditional Swedish delicacies. The most important characteristic of this food is the persistent stench, root according to the relevant experimental data, the smell of canned herring is 300 times more than that of natto, so even if the canned herring as food. The Swedish government also stipulates that it is not allowed to open the canned herring in residential areas.