Viili

Viili (Finnish viili, Swedish fil) is a yogurt-like mesophilic fermented milk that originated in the Nordic countries. This cultured milk product is the result of microbial action of lactic acid bacteria (LAB). The bacteria strains used in its production produce exopolysaccharides which gives viili a ropey, gelatinous consistency and a pleasantly mild taste resulting from lactic acid.

Viili also has a surface-growing yeast-like fungus Geotrichum candidum present in milk, which forms a velvet-like surface. In addition, most traditional viili cultures also contain yeast strains such as Kluveromyces marxianus and Pichia fermentans. The LAB identified in viili including Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. ''lactis biovar. diacetylactis, Leuconostoc mesenteroides'' subsp. cremoris. Among those mesophilic LAB strains, the slime-forming ''Lc. lactis'' subsp. cremoris produce a phosphate-containing heteropolysaccharide, named viilian.

It is the modern version of the traditional product called filbunke. In modern practice, pasteurized milk is used, fermentation is carried out in a dairy plant in controlled conditions using laboratory-grown cultures and the product sold fresh.

Cream viili (Finnish: kermaviili, Swedish: gräddfil) is made from cream instead of milk, and is used in cooking like sour cream, or with dill, chives and other spices as cold sauce for fish, or as a base for dip sauces.