Soured Milk
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Soured milk is prepared from whole milk via fermentation by lactic acid bacteria such as Lactococcus, Leuconostoc, and Lactobacillus bacteria. It is similar to yogurt and kefir, but the different kind of bacteria give a different taste. The American buttermilk is similar, but soured milk has a thicker consistency. It is of the cuisine of Norway, Sweden, Finland and Germany. 

In German, it is known as Sauermilch or Dickmilch; in Swedish, filmjölk; in Norwegian, surmelk or kulturmelk, and in Finnish, piimä or viili.

Soured milk is usually sold in 1-litre packages. Soured milk may be used in the same way as yogurt, that is, from a bowl using a spoon (with cereals, muesli or corn flakes) or from a glass. Flavor may be added with fruits or berries, for instance strawberries, or by adding sugar. Most people who like yogurt usually like soured milk too. A range of different Lactobacilli strains have been grown in the laboratories, providing a whole range of different kinds of soured milk, with different tastes.

There is a variety of soured milk, soured whole milk i.e. ropy sour milk, which has a consistency thick enough to be gelatinous. It is more sour, and may require an acquired taste. In Swedish, this is known as fil; in Finnish, viili. Its usage is very much like that of yogurt, but as it is very sour, it is not pre-mixed with anything. Instead, the muesli, berries etc. are added into it immediately before eating.

As is the case with most yogurts and kephirs, the Lactobacilli, which are a part of healthy intestinal flora, are alive in the vendible product. Consequently, sour milk has a stabilizing effect on the intestinal flora. Some reports suggest that it contains peptides (casokinins and lactokinins) that act as naturally occurring ACE inhibitors and hence have an antihypertensive effect (Seppo et al 2003).

Soured milk is also popular in South Africa, called "amasi" in isiZulu and isiXhosa, and "maas" in Afrikaans.