Pecorino is one of Italy's oldest cheeses, and over the centuries there have been very few changes in the way it is made. Over the course of 2000 years, the cheesemaking traditions and techniques have been handed down orally. The methods used to coagulate the milk, break the curd, press, drain, scald and salt the cheese vary, depending on the type of Pecorino being produced. The best Pecorino is made between May and June, and is made from the milk taken from sheep grazing on spring pastures. Pecorino can be either mild or mature. The mild variety should be consumed shortly after it is made, while the second is seasoned in a cool, fresh cellar with low ventilation, so that it matures fully. In addition to the fresh and seasoned varieties, there are also more delicately flavoured types of Pecorino (with the addition of cow's milk), and some varieties are even flavoured with herbs or Norcia black truffle. Other varieties require specific ageing processes: "pecorino di fossa" is aged in special straw-lined caves, while pecorino di cenere is matured under a layer of ash.