Butter is commonly produced from cow's milk, but it can also be made with goat and sheep's milk. Making butter involves churning the cream from the milk until it's separated into butterfat solids and liquid buttermilk. Some manufacturers add bacterial cultures to the cream during production. This ripening step ferments the milk sugars, like lactose, and converts them to lactic acid, adding a slight tanginess. Salt can be added as a preservative and to add a savory taste. Butter is pale white to yellow or more golden, with coloring agents added like carotene.