Clarified butter has almost all of its water and milk solids removed, leaving almost-pure butterfat. Clarified butter is made by heating butter to its melting point and then allowing it to cool; after settling, the remaining components separate by density. At the top, whey proteins form a skin, which is removed. The resulting butterfat is then poured off from the mixture of water and casein proteins that settle to the bottom. Ghee is clarified butter that has been heated to around 120 °C (250 °F) after the water evaporated, turning the milk solids brown. This process flavors the ghee, and also produces antioxidants that help protect it from rancidity. Because of this, ghee can be kept for six to eight months under normal conditions. Whey butter Cream may be separated (usually by a centrifuge or a sedimentation) from whey instead of milk, as a byproduct of cheese-making. Whey butter may be made from whey cream. Whey cream and butter have a lower fat content and taste more salty, tangy and "cheesy". They are also cheaper to make than "sweet" cream and butter. The fat content of whey is low, so 1000 pounds of whey will typically give only three pounds of butter. European butters There are several butters produced in Europe with protected geographical indications; these include: Beurre d'Ardenne, from Belgium Beurre d'Isigny, from France Beurre Charentes-Poitou (Which also includes: Beurre des Charentes and Beurre des Deux-Sèvres under the same classification), from France Beurre Rose, from Luxembourg Mantequilla de Soria, from Spain Mantega de l'Alt Urgell i la Cerdanya, from Spain Rucava white butter (Rucavas baltais sviests), from Latvia History Elaine Khosrova traces the invention of butter back to Neolithic-era Africa 8,000 B.C in her book. A later Sumerian tablet, dating to approximately 2,500 BCE, describes the butter making process, from the milking of cattle, while contemporary Sumerian tablets identify butter as a ritual offering. In the Mediterranean climate, unclarified butter spoils quickly, unlike cheese, so it is not a practical method of preserving the nutrients of milk. The ancient Greeks and Romans seemed to have considered butter a food fit more for the northern barbarians. A play by the Greek comic poet Anaxandrides refers to Thracians as boutyrophagoi, "butter-eaters". In his Natural History, Pliny the Elder calls butter "the most delicate of food among barbarous nations" and goes on to describe its medicinal properties. Later, the physician Galen also