The acidity of dromedary milk stored at increases at a slower rate than that of cow milk. Though the preparation of butter from dromedary milk is difficult, it is produced in small amounts by nomads, optimized at 22.5% fat in the cream. In 2001, the ability of dromedary milk to form curd was studied; coagulation did not show curd formation, and had a pH of 4.4. It was much different from curd produced from cow milk, and had a fragile, heterogeneous composition probably composed of casein flakes. Nevertheless, cheese and other dairy products can be made from camel milk. A study found bovine calf rennet could be used to coagulate dromedary milk. A special factory has been set up in Nouakchott to pasteurise and make cheese from camel milk. Mystical beliefs surround the use of camel milk in some places; for example, it may be used as an aphrodisiac in Ethiopia.