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
Danish Blue Cheese Danish Blue Cheese Danablu, often marketed under the trademark Danish Blue Cheese within North America, is a strong, blue-veined cheese. This semi-soft creamery cheese is typically drum- or block-shaped and has a white-to-yellowish, slightly moist, edible rind. Made from full fat cow's milk and homogenised cream, it has a fat content of 25–30% (50–60% in dry matter) and is aged for eight to twelve weeks. Before ageing, copper wires or rods are used to pierce the formed curds to distribute the mould ("Penicillium roqueforti") evenly through the cheese. The holes can still be seen when the finished wheel is cut