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Viili

Regional

Finland and other Nordic countries

A traditional Finnish fermented milk distinguished by a thick and characteristically ropy texture produced by its starter culture.

About Viili

Viili is a traditional Finnish fermented milk distinguished by its thick, viscous, and characteristically ropy or stringy texture. When a spoon is lifted from a bowl of viili, the milk stretches into long, elastic threads rather than breaking cleanly — a property produced by the exopolysaccharides (long-chain sugars) secreted by the bacteria in its starter culture. This unique texture has made viili a distinctive and recognisable part of Finnish dairy tradition.

Viili is made using a mesophilic (moderate-temperature) mixed-strain starter culture dominated by Lactococcus lactis strains, particularly exopolysaccharide-producing Lactococcus lactis subsp. cremoris. Unlike thermophilic yogurt cultures, which require warm incubation temperatures (around 40–45°C), viili ferments at room temperature (around 18–20°C), making it historically simple to produce in Finnish homes without specialised equipment. The fermentation takes approximately 24 hours.

Traditional viili also contains Geotrichum candidum, a mould that grows as a thin, velvety white layer on the surface of the fermented milk. This surface mould contributes to viili's flavour and is considered a sign of authentic traditional production. The taste of viili is mild, slightly tangy, and less acidic than Greek yogurt or standard plain yogurt.

Viili has been made in Finnish homes for hundreds of years, with families maintaining their own starter cultures passed down through generations. Like sourdough bread starter, a viili culture is kept alive by reserving a spoonful of each batch to inoculate the next.

Sources & Further Reading

Codex Alimentarius — Standard for Fermented Milks — International food standard CXS 243-2003 (amended through 2024) — covers fermented milks generally; viili falls within the mesophilic cultured/ropy fermented milk category but is not individually named in the standard
PMC — Viili: A Traditional Finnish Ropy Fermented Milk — Peer-reviewed research describing viili as a Finnish mesophilic fermented milk, its exopolysaccharide-producing Lactococcus lactis subsp. cremoris starter, Geotrichum candidum surface mould, and ropy texture characteristics

Nutrition

Viili's nutritional composition is similar to that of other fermented whole milks and depends on the fat content of the starting milk. As a fermented product, some lactose is converted to lactic acid during fermentation. Typical characteristics:

FatVaries with milk used

ProteinSimilar to plain yogurt

LactoseReduced by fermentation

Live CulturesPresent at consumption

Viili contains live lactic acid bacteria at the time of consumption, similar to yogurt. It provides calcium, protein, and B vitamins from the milk, along with the benefits associated with live fermented foods. Its mild flavour makes it suitable for people who find plain yogurt too sharp or acidic.

Common Uses

◌ Eaten plain ◌ With berries ◌ With sugar or honey ◌ Breakfast food ◌ With cereal

Viili is most commonly eaten plain at breakfast or as a snack, typically topped with fresh or preserved berries (such as lingonberries or blueberries), sugar, or a drizzle of honey. It is eaten directly from the container it was fermented in rather than being stirred or poured — stirring breaks the ropy gel structure. In Finland, viili is part of everyday home cooking and is available commercially in supermarkets throughout the country.

Interesting Facts

Viili's signature ropy, stretchy texture is caused by exopolysaccharides — long-chain sugars secreted by Lactococcus lactis subsp. cremoris strains in the starter culture.
Unlike yogurt, viili ferments at room temperature (around 18–20°C) and requires no heating or incubation equipment — historically making it easy for Finnish households to produce year-round.
Traditional viili develops a thin surface layer of Geotrichum candidum mould, giving it a slightly velvety white top, which is a hallmark of authentic traditional production.
Viili starter cultures are passed down through generations like sourdough starters — a spoonful of each batch is reserved to inoculate the next one.
Viili is one of several Nordic ropy fermented milks; related products include Swedish långfil and Norwegian tettemelk, all characterised by similar stretchy textures from exopolysaccharide-producing cultures.