Yoghurt or yogurt, or less commonly yoghourt or yogourt, is a dairy product produced by bacterial fermentation of milk. It can be made from any milk, including soy milk, but modern production is dominated by cow milk. The fermentation of milk sugar (lactose) produces lactic acid, which acts on milk protein to give yoghurt its gel-like texture and characteristic tang. Yoghurt is often sold in a fruit, vanilla, or chocolate flavor, but can be unflavored.