Viili is a very interesting type of yogurt, original from Scandinavia and prepared not just in Finland, but also in Sweden, with a velvety but rather slimy consistency. There are two different types of viili prepared in Finland, which are called the “short” and “long” versions. The short version looks very much like regular yogurt that is found in stores, having a mild and pleasant taste. The long version has a ropy texture, even elastic, and has a beautiful honey-like taste and flavor.
Just like other types of Scandinavian fermented milk products, viili is also made by using mesophilic cultures, which can develop without a problem at lower temperatures than usually required for milk’s fermentation process. The aspect and texture of viili are due to the action of the lactic acid bacteria and a fungus, Geotrichum candidum, which is present in milk and likes growing at the surface, making viili develop a soft velvety layer at the top. Besides this, traditionally prepared viili can contain other types of yeasts in their culture, such as Kluveromyces marxianus and Pichia fermentans. Concerning the lactic acid bacteria used for the fermentation of viili, there are several options in this case. Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis biovar. diacetylactis, Leuconostoc mesenteroides subsp. cremoris, they can all be used with success. But it is Lc. lactis subsp. cremoris which turns viili’s consistency in its well-known sliminess. This mesophilic bacteria creates a heteropolysaccharide that contains phosphates, named viilian, which coagulates the product in the end. As mentioned earlier, there are two types of viili, with different consistency, an aspect that is influenced by the types of bacteria used.
So, if you want to get the intriguing long type of viili, the one that is slimy and slides on the walls of your bowl and in your spoon, making its consumption an adventure you never experienced with yogurts before, you will need Lactococcus lactis subsp. cremoris. But, you can also make viili from a previous batch of yogurt. You will need two teaspoons of viili for a cup of whole milk. Take the teaspoons of viili and stretch them across the walls of a bowl, coating them with this yogurt. Then add the cup of milk, cover the bowl, and allow it to ferment on your countertop for 12 to 24 hours. You will know that your viili is ready when you have a thick, soft, and slimy texture on the spoon. Refrigerate what you don’t consume, so you will enjoy it later or in the following days.