Cream cultures

Cream cultures such as sour cream, crème fraiche, and buttermilk are indigenous to Western and Northern Europe. These products result from the slow fermentation produced by the mesophilic bacteria Lactococci and leuconostoc species. These bacteria have three important characteristics that make them ideal for production of creams and buttermilk: 1. They grow best at moderate temperatures. The process of fermentation can be kept at lower temperatures than those that produce yogurt. 2. They are moderate acid producers. Again, it prevents the formation of yogurt from too acidic a condition. 3. They complement flavor by turning citrate into diacetyl; a compound which gives the fermented milk product a characteristic buttery flavor.