Yogurt, yoghurt, or yoghourt (/ˈjoʊɡərt/ or /ˈjɒɡərt/; from Turkish: yoğurt) is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as yogurt cultures. Fermentation of lactose by these bacteria produces lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor. Cow’s milk is commonly available worldwide, and, as such, is the milk most commonly used to make yogurt. Milk from water buffalo, goats, ewes, mares, camels, and yaks is also used to produce yogurt where available locally. The milk used may be homogenized or not, even pasteurized or raw. Each type of milk produces substantially different results.