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Fermented milk from Lapland and northern Scandinavia

Tätmjölk (butterwort-started ropy milk)tätmjölk

Tätmjölk (Norwegian tettemelk) is the old ropy sour milk that folklore says was started by adding leaves of common butterwort (Pinguicula vulgaris) to milk, then kept going by backslopping. A leaf study found lactococci, and genes for exopolysaccharide, on the plant, which fits the folklore. The leaf practice is no longer used.

A short entry: the sources we found record only what is said here about Tätmjölk itself.

Short entryFermented milk

Recipe

No fixed amounts recordedNo amounts are recorded.
Fresh cow milk
Leaves of common butterwort (Pinguicula vulgaris)The traditional starter in the folklore[porcellato2016]
Starterother: butterwort leaves in the folklore
Start
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What changes: Fresh butterwort leaves go into the milk vessel

Step 1 of 3
Put butterwort leaves into the milk vessel
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactococcus lactis

Output: seeded milk.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

lactococci on the leaves enter the milk

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Tätmjölk (Norwegian tettemelk) is the old ropy sour milk that folklore says was started by adding leaves of common butterwort (Pinguicula vulgaris) to milk, then kept going by backslopping. A leaf study found lactococci, and genes for exopolysaccharide, on the plant, which fits the folklore. The leaf practice is no longer used. Exopolysaccharide-producing Lactococcus lactis subsp. cremoris, the strain behind the ropy texture of Nordic ropy milks does most of the fermenting.

What makes this one different

The starter was a plant, butterwort leaves, rather than an earlier batch or a bought culture; the ropy texture comes from the same lactococci as långfil and viili.

Related ferments

Safety

A folk practice no longer used; a butterwort leaf is not a controlled starter.

History and sources

Every number is labelled with how it is known. How this atlas is made

Linnaeus described the use of butterwort to curdle milk in his Flora Lapponica (1737, p. 10). In 1874 Darwin and his son tried milk with Pinguicula and noted that the same plan was used in Wales.

  1. [porcellato2016] Porcellato D., Tranvåg M., Narvhus J. 2016, Presence of Lactococcus and lactococcal exopolysaccharide operons on the leaves of Pinguicula vulgaris supports the traditional source of bacteria present in Scandinavian ropy fermented milk, Journal of Dairy Science 99:7049–7052 (abstract)paper
  2. [rampanti2024] Rampanti G. et al. 2024, Technological and enzymatic characterization of autochthonous lactic acid bacteria isolated from viili natural starters, Foods 13:1115paper
  3. [darwinproject] Darwin Correspondence Project, letter DCP-LETT-9515 (C. Darwin, June 1874, on Pinguicula and milk; notes cite Linnaeus 1737, p. 10)archive