ricotta

The production of ricotta in the Italian peninsula dates back to the Bronze Age. In the second millennium BC, ceramic vessels called milk boilers started to appear frequently and were apparently unique to the peninsula. These were designed to boil milk yet prevent it from boiling over. The fresh acid-coagulated cheeses produced with these boilers were probably made with whole milk.
The production of rennet-coagulated cheese, though, overtook the production of fresh whole-milk cheeses during the first millennium BC. Bronze cheese graters found in the graves of the Etruscan elite prove that hard-grating cheeses were popular with the aristocracy. Cheese graters were also commonly used in ancient Roman kitchens. Unlike the fresh acid-coagulated cheese, aged rennet-coagulated cheese could be preserved for much longer.
The increased production of rennet-coagulated cheese led to a large supply of sweet whey as a byproduct. Cheesemakers then started using a new recipe, which used a mixture of whey and milk to make the traditional ricotta as it is known today.
The ancient Romans made ricotta, but writers on agriculture, such as Cato the Elder, Marcus Terentius Varro, and Columella, do not mention it. They described the production of rennet-coagulated cheese, but did not write about milk boilers or acid-coagulated cheese. A likely reason is that ricotta was not profitable because its very short shelf life did not allow distribution to urban markets. Ricotta was most likely consumed by the herders who made it. Even so, evidence from paintings and literature indicates that ricotta was known and likely eaten by Roman aristocrats, as well.
Ceramic milk boilers were still used by Apennine herders to make ricotta in the 19th century AD. Today, metal milk boilers are used, but…

Whey proteins are some of the many kinds of milk proteins. The production process entails the use of heat and acid to coagulate whey protein from whey solution. The whey solution is heated to a near-boiling temperature, much hotter than during the production of the original cheese, of which the whey is a remnant.

Ricotta di bufala campana and ricotta romana are notable varieties produced in Italy and protected by the European Union's protected designation of origin regulation. Ricotta di bufala campana is made from the whey left over after the production of mozzarella di bufala campana, a protected variety of buffalo mozzarella. Ricotta romana is made from the whey of sheep milk.

Fresh ricotta can be subject to extra processing to produce variants which have a much longer shelf life. These production methods include salting, baking, smoking, and further fermentation.
Ricotta salata is a pressed, salted, dried, and aged variety of the cheese, typically using ricottas made with sheep's milk sourced from Lazio. It is milky-white and firm, and is used as a table cheese or for grating or shaving over dishes, particularly pastas made fresh from water and flour. Ricotta salata is sold in wheels, decorated by a delicate basket-weave pattern.
Ricotta infornata (lit. 'baked ricotta') is produced by placing a large lump of soft ricotta in the oven until it develops a brown, lightly charred crust, sometimes even until it becomes sandy brown all the way through. Ricotta infornata is popular primarily in Sardinia and Sicily, and is sometimes called ricotta al forno.
Ricotta affumicata (lit. 'smoked ricotta') is similar to ricotta infornata and is produced by placing a lump of soft ricotta in a smoker until it develops a grey crust and acquires a charred wood scent, usually of oak or chestnut wood, although, in Friuli, beech wood is used, with the addition of juniper and herbs.
Ricotta forte, also known as ricotta scanta, is produced from leftovers of any combination of cow, goat, or sheep milk ricotta. These are allowed to age for about a year, during which salt is added and the cheese mixed every two or three days to prevent the growth of mold. The end result is a soft and creamy brown paste which has a very pungent and piquant taste. It is produced in the southern part of the province of Lecce and sold in glass jars. It is smeared on bread, mixed with tomato sauces for pasta, or added to vegetable dishes.