Once milk is collected, it must be prepared and treated. The production of fermented milks is generally the same as yoghurt. Only the type of microorganisms used and the fermentation process (time, temperature) varies.
Standardization of milk
The composition of milk is modified to reduce the fat content and to increase milk solids with the addition of concentrated milk or milk powder.
Homogenisation and Pasteurisation
Once the milk solids have adjusted, it is homogenised. This is the process of breaking up the fat globules in milk to prevent it from separating and giving it a more uniform and smooth product. The milk is then pasteurised (heated at high temperature below boiling point - 90°C) for a specified period of time (several minutes) in order to destroy pathogenic microorganisms.
Cooling and Fermentation
Once the milk has been pasteurised it is then cooled to 42-46°C. At this stage, the live, active bacteria , L. bulgaricus and S. thermophilus for yoghurt (and additional or different (probiotic) bacteria as the case may be) are then added to the milk. The milk is kept at the same temperature for 3-4 hours to allow the bacteria to incubate and ferment, producing the lactic acid that coagulates milk.
Depending on the type and texture of fermented milk being made, the method of production will differ. Set or stirred or made into a drinking beverage, fermented milks are treated in separate containers to gel or in vats to be shaken and whipped.
Common additions to fermented milks include different flavourings, sweeteners, extracts, blended or pureed fruit prior to, or after fermentation.