Isterband is a sausage which is made from beef, pork, boiled potatoes or par-boiled pearl-barbley and sometimes broth.
The characteristic sour taste comes from lactic acid bacteria, which is a key ingredient in this typical Swedish sausage from Småland. Isterband was in the olden days very popular at Christmas dinners and buffets in southern Sweden. In Vetlanda this sausage was/is often referred to as "hanging sausages" - "hängekorv". And this because of its origin where the sausage hung to dry in front of the fireplace. It was this process which allowed the lactic acid bacteria to thrive and give the sausage its naturally sour flavor.
There are large variations, both for dried and smoked Isterband, as well as in terms of acidity, fat/meat content and saltiness. Isterband from Småland has the sour taste that comes from lactic acid bacteria.
It is is usually served fried in a frying pan with, for example, dill potatoes and pickled beets. It is said that Isterband is the only genuine Swedish sausage, which has no counterpart in other countries.