Soured milk is a milk product that may be produced in different ways. The milk is either fermented with lactic acid bacteria and then sometimes called fermented or cultured milk or it acquires its sour taste through the addition of an acid - for example acetic acid or citric acid. Soured milk produced this way is also called acidified milk. The term sour milk is often used synonym but may relate to milk that has spoiled uncontrolled as well. Before lactic acid bacteria are injected, the milk is brought to the desired fat content (for example low-fat) and is pasteurised and homogenised. The injected milk is then heated to a certain temperature to ferment. Depending on the used bacteria the sourness of the end product may be determined. As soon as the correct degree of sourness is achieved, the milk is cooled to stop the bacteria from making the milk too sour. The sourness is a natural preservative, which is why soured milk products have a longer shelf life than regular pasteurised milk products. Soured milk products can be distinguished by three factors: taste, texture and fat content.

• Each producer has its own specific taste. It reaches from mild to strongly sour. To achieve this taste certain bacteria are used and the fermentation is stopped at a specific point.
• The texture of a sour milk product may be between quite firm and almost liquid. This depends largely on the container it has been fermented in. It is usually quite firm, when it is sold in the container it has been fermented in and more liquid when fermented in large tanks. Tank-fermented soured milk has to be stirred smooth in order to fill it in smaller containers. It is then drinkable.
• The fat content of soured milk is adjusted before fermentation through a mixture of skim milk and cream. Where the label of soured milk products does not state the fat content, it is usually produced from whole milk of 3.5 to 4% fat.

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Sour milk products

• buttermilk
• crème double
• crème fraīche
• thick sour milk
• yoghurt
• kefir
• fruit sour milk drinks
• sour cream
• smetana
• whey drinks
• sour milk drinks
• filmjölk

Note: It is easy to determine if unopened soured milk products are spoiled. If the lid is taut and curves to the top, the soured milk is spoiled. No rule without exception though: Kefir develops its full taste only towards the end of its shelf life, when it develops a light carbonation that arches the lid to the top.

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Fruit sour milk drinks:

Fruits or fruit products are added to soured milk products in two different ways.

• The finished, fermented and thickened milk product (for example yoghurt or thick soured milk) are filled into containers that already contain the fruits. The fruits are then at the bottom of the container that is sold.
• The fruits or fruit sauce are stirred into the soured milk product.

Fruit products that are used in milk products may contain the following ingredients but should be declared on the label:

• fruits and fruit pieces
• fruit juices or syrup
• flavouring substances
• sugar
• binders
• preservatives

It also has to be stated which type of fruits were used and how high the percentage of fruits in the product is. Each country has its own regulations concerning the amount of fruits that have to be added.

See also:
butter,
Crème double,
Crème fraīche,
yoghurt,
coffee cream,
kefir,
evaporated milk,
whey,
quark,
milk protein,
milk products,
milk fat,
powdered milk,
lactic acid,
lactic acid bacteria,
milk plasma,
creamy sour milk,
sour cream,
whipping cream,
cream,
smetana,
sour milk,
filmjölk,
and
whole milk powder.

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