Their different styles and flavors depend on the origin of the milk and whether it has been pasteurized . It also depends on the butterfat content , the species of bacteria and mold , and the processing including the length of aging . Their styles , textures and flavors depend on the origin of the milk ( including the animal 's diet ) , whether they have been pasteurized , the butterfat content , the bacteria and mold , the processing , and aging .