Blue cheese of blue veins. The distinctive flavor and aroma of blue cheese arises from methyl ketones (including 2-pentanone, 2-heptanone, and 2-nonanone) which are a metabolic product of "Penicillium roqueforti". These compounds are not formed in other types of cheese fermented by bacterial acidification alone. In the European Union, many blue cheeses, such as Cabrales, Danablu, Gorgonzola, Roquefort and Blue Stilton, carry a protected designation of origin, meaning they can bear the name only if they have been made in a particular region. Similarly, individual countries have protections of their own such as France's Appellation d'Origine Contrôlée and Italy's Denominazione di Origine
Sheep milk cheese content. Sheep milk contains 4.8% lactose, more lactose than cow milk, and is therefore not an alternative for people who are lactose intolerant. Though sheep's milk may be drunk in fresh form, today it is used predominantly in cheese and yogurt making. Well-known cheeses made from sheep milk include the Feta of Bulgaria and Greece, Roquefort of France, Manchego from Spain, the Pecorino Romano (the Italian word for sheep is "pecore") and Ricotta of Italy. Yogurts, especially some forms of strained yogurt, may also be made from sheep milk. Many of these products are now often made with cow's milk,