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
Wensleydale cheese Lower Wensleydale. They brought with them a recipe for making cheese from sheep's milk. During the 14th century cows' milk began to be used instead, and the character of the cheese began to change. A little ewes' milk was still mixed in since it gave a more open texture, and allowed the development of the blue mould. At that time, Wensleydale was almost always blue with the white variety almost unknown. Nowadays, the opposite is true, with blue Wensleydale rarely seen. When the monastery was dissolved in 1540, the local farmers continued making the cheese until the Second World War,