Långfil and tettemelk

What långfil and tettemelk are

Långfil and tettemelk are northern Scandinavian cultured milks known for how they stretch. Where ordinary cultured milk sets to a short curd, these develop a viscous, elastic body that can be drawn into long threads on a spoon. Långfil is the Swedish name, with långmjölk and tätmjölk as relatives; in Norway the words are tettemelk or tettemjølk, and tjukkmjølk belongs especially to the Røros district. They are close but not one recipe or one culture.

The ingredients are milk and a living starter, Swedish täte and Norwegian tette. A suitable starter holds bacteria that make extracellular polymers, which give the ropy body. Lactococci lead, above all strains long called Lactococcus lactis subsp. cremoris, now Lactococcus cremoris, and they also ferment lactose to lactic acid for the sour taste and thickening. The milk is mild and cleanly sour, white to cream, like a thick pudding when freshly set and more fluid when stirred or shaken. The Norwegian dairy information service calls tettemelk full-bodied and slightly chewy, and the strings are intended, not spoilage.

Households kept the culture alive by moving a little finished milk into fresh milk, and borrowed starter from a neighbour if their own was lost. Tradition also ties the first culture to butterwort, Pinguicula vulgaris, tettegras in Norway and tätört in Sweden. Researchers have found lactococci and exopolysaccharide genes on butterwort leaves, which does not make collected wild leaves a reliable or safe way to ferment milk.

Långfil and tettemelk sit in a Nordic family of mesophilic cultured milks with Swedish filmjölk and Finnish viili, and they are not interchangeable. Ordinary filmjölk lacks the long texture, and traditional viili may carry a surface layer of Geotrichum candidum that långfil and tettemelk do not need. What defines them is a maintained, ropy lactic starter used on milk, usually cow's milk.

The record of its past

Ropy cultured milk is documented in northern Scandinavia from at least the early eighteenth century. Jonas Ramus linked tettegras to thickened milk in his Norriges Beskrivelse of 1735, and Carl Linnaeus met string-forming fermented milk on his Lapland journey in 1732 and noted the practice of putting a little finished milk into another batch. Nils Gisler described tätmjölk preparation in 1749 and Johan Ernst Gunnerus wrote a Norwegian dairy treatise in 1774. These attest the practice and not its date of origin.

The tradition mattered where summer dairy work had to carry households through leaner seasons. In Sweden it belonged to northern and central farming districts and the summer pasture dairies, fäbodar, and the Swedish Institute for Language and Folklore holds accounts of retained starter, its passing between households and storage in cool buildings. A Haverö recipe in Medelpad, collected by Stina Sahlin from J. Olsson in 1897, specifies skimmed milk and retained tätte, and a Leksand account of 1928 describes keeping a culture going by daily renewal.

Norway's protected-name regulation records tjukkmjølk in Røros and Nord-Østerdal from at least the 1850s, as an important food for mining families. Both Norwegian and Swedish records describe keeping starter on pieces of linen or cotton dipped in cultured milk and dried, a way to carry a living culture before refrigeration.

The butterwort story is more tangled. Older descriptions use its leaves to start fermentation, though attempts to repeat it often fail. Kjell Furuset argued in 2008 that the plant's protein-coagulating enzymes belonged to an older, drained-milk preparation and are not needed for modern ropy tettemelk, and a 2016 dairy microbiology study found Lactococcus and polysaccharide genes on butterwort leaves, which makes a microbial link plausible without giving a dependable wild starter.

Industrial dates are firm. Arla records commercial Swedish långfil from 1965. In Norway, local tette cultures were collected and compared in 1995, Rørosmeieriet began production in 1996, and the name Økologisk Tjukkmjølk fra Røros was protected in 2004, with a culture combining three regional starters from Røros, Os and Tolga.

The bacteria and the strings

Two microbial jobs give långfil its character: making lactic acid and making extracellular polymers. The main organisms are mesophilic lactococci, with other lactococci and small numbers of Leuconostoc in mixed cultures, and yeasts reported in traditional Nordic milks though no yeast is needed to explain normal långfil or tettemelk.

Lactococci split lactose with beta-galactosidase, take the sugars through glycolysis, and lactate dehydrogenase turns pyruvate into lactic acid while regenerating NAD+. As acid rises, colloidal calcium phosphate dissolves from the casein micelles, the network loses stability, and near pH 4.6 the proteins gel. That explains souring and curd, but not the long strings.

The strings come from bacterial exopolysaccharide, which raises viscosity and gives an elastic, thread-forming body. A 1991 study isolated a slime-forming strain, Lactococcus lactis subsp. cremoris LAPT 3001, from Swedish långfil; its purified capsule contained rhamnose, glucose, galactose, glycerol and phosphorus and was read as probably deacylated lipoteichoic acid. That describes the strain and not every ropy culture. Polymer output depends on strain genetics, growth conditions and the milk, so a generic yoghurt culture can acidify and thicken the milk while losing the defining texture.

Butterwort brings in a separate mechanism: its leaves hold protein-degrading enzymes that can coagulate milk, which is enzymatic curdling and not acidification or polymer production. In 2016 researchers checked 20 Pinguicula vulgaris leaf samples from five Norwegian places and four commercial tettemelk samples, found Lactococcus on every leaf and lactococcal EPS-associated genes on 14. DNA detection does not show that untreated leaves make safe milk, and the finished product should be made with an authenticated active culture.

How it is made and why

The ingredients are milk and an established ropy starter. Cow's milk is the usual base; whole milk gives a fuller product, and skimmed milk was common historically because cream was kept for butter. The starter supplies the lactococci that acidify and make the strings, and an ordinary yoghurt or filmjölk starter is not necessarily suitable.

The household recipe here is the Haverö one: 3 litres of skimmed milk and 1 decilitre of fresh tätte, meaning retained thick cultured milk. The milk is warmed to 15 to 18 C, the tätte is mixed in, and the milk stands in a warm room for a day to set, then goes to a cold cellar. The text claims the finished milk kept as long as six months in a suitable cellar, a storage custom and not a modern shelf life. It says nothing on pasteurisation, which predates the recipe, and gives no room temperature for the day's standing.

A Leksand account of 1928 mixes three or four tablespoons of mature tätmjölk into a litre of fresh milk held at about 15 to 20 C and expects the next day's milk to be thick. It says the culture must be renewed regularly and that the stringiness disappears if the starter is neglected.

Norway's protected Røros product gives a controlled comparison: organic milk, skimmed and pasteurised but not homogenised, a traditional tette culture at 0.5 to 1.5 per cent, held at 20 to 23 C for about a day until the consistency develops, filled into cartons on the day and fermented in a controlled facility, with the culture renewed regularly. These are specifications for a named Norwegian product, not a Swedish långfil recipe.

Each step has a job. Pasteurisation cuts milk-borne hazards, cooling before inoculation protects the starter, mixing spreads the bacteria, controlled incubation lets acid and polymer develop, and refrigeration slows change. Leaving the set milk undisturbed keeps the gel coherent, though the finished milk may be stirred. Butterwort expresses a traditional belief and is not a modern starter or safety method.

Variations

Swedish records describe a family of ropy milks and not one fixed product: långmjölk, tätmjölk, tjockmjölk, segmjölk and källarmjölk. They are tied to central and northern Sweden and seasonal summer pastures. In some districts the milk was skimmed first and elsewhere richer milk was used, and texture, acidity and storage depended on the culture and household. The commercial term långfil does not reproduce every historical version.

The archive records differences in detail. The Haverö recipe uses skimmed milk and fresh tätte, the Leksand account describes a culture renewed with fresh milk each evening, and a 1939 collection from Valbo in Gästrikland remembers making starter from butterwort gathered near the summer pastures and adding milk in stages until it turned stringy. They are ethnography, not controlled microbiology.

Norwegian tettemelk covers the Røros and Nord-Østerdal tradition and northern variants, and tettemjølk and tjukkmjølk are broadly similar products. Store norske leksikon names kjellermelk as a related cellar-stored milk, generally less viscous, and settmelk as a concentrated preparation with whey removed, which is not the same as ordinary undrained tettemelk.

Økologisk Tjukkmjølk fra Røros is the most standardised version. In 1995 local groups gathered and compared household starters, the commercial culture drew on three traditions from Røros, Os and Tolga, production began in 1996 and protection followed in 2004. It is sold at different fat levels, including 1.5 and 4 per cent, keeping the mild acidity and elastic texture. Finnish viili and Swedish filmjölk are related but separate products.

Eating and using it

It is eaten from a bowl or stirred until drinkable. Fresh milk can be as thick as a pudding, and shaking or stirring breaks the gel. The flavour is mildly sour and aromatic, and the basic milk needs no sugar or flavouring.

Swedish records put it in ordinary meals. The 1897 Haverö recipe says the tjockmjölk was eaten alone or with porridge, bread or potatoes at midday or evening in warm summer weather, and other folklore accounts use cultured milk with grain foods and as a refresher during farm work. Røros dairy material describes eating tjukkmjølk plain, with flatbread or with breakfast cereals, and the current product suggests muesli, berries and porridge, smoothies and breakfast bowls.

Rørosmeieriet also cooks with it in waffles, sveler, dressings, dips, soups, sauces, marinades and desserts. In baking the milk adds moisture and acid, which can react with bicarbonate of soda to give gas. Strong heat may destabilise the acidified protein, so it behaves differently in cold sauces and hot dishes.

The culture itself was a household resource: a little finished milk was kept to start the next batch, neighbours swapped starters, and accounts describe drying culture on textile for later use or travel. That preserved the means of making more cultured milk, but its safety and viability were not guaranteed. Långfil and tettemelk should be kept apart from strained curds, skyr, kefir and viili when indexing dishes.

Reading results and problems

A good batch smells mildly acid and cleanly of milk, and when a spoon is lifted the milk stretches into threads. How stringy depends on the starter and process. Norway's Røros specification describes a firm, full-bodied, pudding-like product that thins when stirred or shaken. A less elastic batch may still be properly soured milk without the defining character.

Loss of stringiness usually points to the culture. Ropy texture needs bacteria that keep the ability to make extracellular material, and a plain lactic starter will acidify milk without strands. Temperature, milk, starter age and repeated propagation also matter, and the Leksand account records the stringiness fading when the culture was neglected. Adding generic yoghurt culture does not restore a lost ropy trait.

A batch that stays thin and sweet has not acidified enough: inactive starter, wrong temperature, contamination or poor handling. A very sour, separated or grainy one has gone past its endpoint or the gel was disturbed. The ropy polymers hold water but cannot make up for every process failure, and both acid and consistency count in judging a batch.

Mixed traditional communities can include lactococci, leuconostocs and occasionally yeasts or moulds, but vigorous bubbling, swollen containers, alcoholic smell or visible mould are not characteristics of modern långfil or Røros tjukkmjølk, and surface growth that is normal on some viili is no reason to accept mould here. Do not repair a poor batch by re-warming or adding starter of unknown character.

Butterwort needs caution: the 2016 study found Lactococcus DNA in all 20 leaf samples and EPS genes in 14, among other bacteria, which supports a possible historical source but does not make a leaf a safe starter. Wild-leaf inoculation should not stand in for an established food-grade culture.

The historical six-month cellar storage and Rørosmeieriet's shelf life for its packaged product do not carry over to homemade milk. Raw milk can carry Campylobacter, pathogenic E. coli, Listeria, Brucella and Salmonella. Use pasteurised milk, clean equipment, a characterised starter, a verified acid endpoint and prompt refrigeration. Sourness, stringiness and a history of successful backslopping are not proof against pathogens. GABA has been measured in tjukkmjølk, which does not establish a particular health benefit.