Pecorino Romano is rubbed with oil and wood ash. Fresco or young cheeses usually have a very white paste which can be quite crumbly in texture. The paste darkens and hardens as the cheese matures. Really mature Pecorino can be very hard with casein crystals.
In the hills of central and southern Italy, cows are rare. Instead ewe's milk is used to make hard compact cheeses which are generally known as Pecorino. Each region has its own type. Pecorino may be sold fresh, medium, or mature, and the rind tends to vary in color depending on the whim of the producer.
Aromas and flavors, too, change as the cheese matures. The young cheese can be quite mild with just a light touch of lemon, whereas older cheeses can be extremely piquant and salty. Almost all cheeses have a touch of nuttiness and the characteristic lemony tang of a ewe's-milk cheese.