Ricotta is produced from whey, the liquid separated out from the curds when cheese is made. Most of the milk protein (especially casein) is removed when cheese is made, but some protein remains in the whey, mostly albumin. This remaining protein can be harvested if the whey is first allowed to become more acidic by additional fermentation (by letting it sit for 12-24 hours at room temperature). Then the acidified whey is heated to near boiling. The combination of low pH and high temperature causes additional protein to precipitate out, forming a fine curd. Once cooled, the curd is separated by passing though a fine cloth.
After realizing that whey cannot be safely dumped as it creates an environmental hazard , Romano makers discovered that when the protein-rich substance is heated, whey protein particles fuse and create a curd. This curd, after drainage, is ricotta. Because ricotta is made from whey, rather than milk, it is a whey cheese, not technically a "cheese.
Ricotta is a fresh cheese (as opposed to ripened or aged), grainy and creamy white in appearance, slightly sweet in taste, and contains around 5% fat. In this form, it is somewhat similar in texture to some cottage cheese variants, though considerably lighter. Like many fresh cheeses, it is highly perishable. Ricotta comes in other forms as well, see variants below.
In Italian households and dining establishments, ricotta is often beaten smooth and mixed with condiments, such as sugar, cinnamon and occasionally chocolate shavings, and served as a dessert. This basic combination (often with additions such as citrus and pistachios) also features prominently as the filling of the crunchy tubular shell of the Sicilian cannoli, and layered with slices of cake in Palermo's cassata.
Combined with eggs and cooked grains, then baked firm, ricotta is also a main ingredient in Naples' pastiera, one of Italy's many "Easter pies" (). Regional variations may be sweet or savory.
Ricotta may also be used in savory dishes, including pasta, pizza, manicotti, lasagna, and ravioli.
It also makes a delicious substitute for mayonnaise in traditional egg or tuna salad and as a sauce thickener.
While Italian Ricotta is typically made from the whey of sheep or water buffalo milk, the American product is almost always made of cow's milk whey. While both types are low in fat and sodium, the Italian version is nutty, slightly sweet and has dry texture, while the American is blander, sweeter, moister, and therefore more neutral in cooking .
In addition to its fresh, soft form, ricotta is also sold in three preparations which ensure a longer shelf life: salted, baked and smoked. The pressed, salted and dried variety of the cheese is known as ricotta salata. A milky-white hard cheese used for grating or shaving, ricotta salata is sold in wheels, decorated by a delicate basket-weave pattern.
Ricotta infornata 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 is similar to ricotta infornata. It 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 scanta is the process of letting the ricotta go sour in a controlled manner, for about a week, then stirring it every 2-3 days, salting occasionally and allowing the liquid to flow away. After about 100 days the ricotta has the consistency of cream cheese with a distinct, pungent, piquant aroma, much like blue cheese but much richer. Ricotta scanta tastes as it smells, extremely aromatic and piquant with a definite bitter note. Tasted with the tip of the tongue, it has a "hot" sensation.