Filmjölk

It is made by fermenting cow's milk with a variety of bacteria from the species Lactococcus lactis and Leuconostoc mesenteroides.

The acid gives filmjölk a sour taste and causes proteins in the milk, mainly casein, to coagulate, thus thickening the final product.

The bacteria also produce a limited amount of diacetyl, a compound with a buttery flavor, which gives filmjölk its characteristic taste.

In the Nordic countries, filmjölk is often eaten with breakfast cereal, muesli or crushed crisp bread on top.

Some people add sugar, jam, apple sauce, cinnamon, ginger, fruits, or berries for extra flavor.

It can also be purchased and is popular in the neighboring country, Lithuania, where it is called rūgpienis or raugintas pienas ('sour/fermented milk').

[1][2][9] fi: pitkäviili Filbunke fi-se: Fil[36] fi: Viili To make filmjölk, a small amount of bacteria from an active batch of filmjölk is normally transferred to pasteurised milk and then left one to two days to ferment at room temperature or in a cool cellar.

In Flora Lapponica (1737), Carl von Linné described a recipe for tätmjölk and wrote that any species of butterwort could be used to make it.

[65] Sundew and butterwort are carnivorous plants that have enzymes that degrade proteins,[68] which make the milk thick.