🥣 Viili

Viili is a Finnish soured milk with an unusual stretchy texture: scoop it with a spoon and it pulls into long strands. The milk is inoculated and left at about 20 °C for 16–24 hours; in a laboratory experiment, 1 g of starter was used per litre of milk and kept for a day at 22.5 °C. This is the work of mesophilic bacteria, which, unlike yogurt bacteria, don't need warmth.

The starter includes lactococci, Lactococcus lactis, which produce acid and aroma, as well as Leuconostoc mesenteroides. The stretchiness comes from long polysaccharides that the lactococci release into the milk; one of them, the phosphopolysaccharide viilian, was described by Japanese scientists in 1999. A yeast-like fungus, Geotrichum candidum, usually grows on the surface of viili and forms a velvety crust.

Neighbouring countries have similar stretchy products: Swedish långfil and Norwegian tettemelk. According to folk tradition, ropy milk was once started with the leaves of the butterwort plant, but this is no longer done, and industrial starters give a product somewhat different from the traditional one. Nutritionally, the closest match is Swedish långfil with 3% fat: 60 kcal and 3.4 g of protein per 100 g.

Viili or yogurt? Yogurt is defined by the Codex Alimentarius as milk soured with thermophilic streptococcus and Lactobacillus bulgaricus in warmth, whereas viili is soured by mesophilic bacteria at about 20 °C for 16–24 hours, so it tastes and spoons differently. People also set it beside kefir and Swedish långfil: all are soured milks, but each rests on its own culture. What marks viili out is the long, stretchy strands and the velvety crust on top.

On a pack look for the Finnish name “viili” (some labels say “soured milk” or “fermented milk”) and the product type, since the word “yogurt” should not appear on it. It is sold chilled in tubs, usually in a dairy or specialist section of a supermarket, next to other cultured milks. Check the date and keep it cold: in Finland pasteurised milk products are stored at 8 °C or below.

Why it matters to you. Viili is not yogurt: under the Codex Alimentarius, yogurt is made specifically with thermophilic streptococcus and Lactobacillus bulgaricus, so the taste and texture here are different. In Finland, products made from pasteurised milk, including viili, are stored at no more than 8 °C. The velvety crust on top is part of the product. Don't believe promises of special benefits from viilian: its effects have been studied only in mice.