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 cuisine in Denmark is mild, there are also stronger Danish cheeses available, some of which are very pungent. Danish Blue cheese can be quite strong, and Danish cheese manufacturers produce molded cheeses that span the range from the mildest and creamiest to the intense blue-veined cheese internationally associated with Denmark. Another strong cheese is "Gamle Ole" (lit: Old Ole - Ole is a man's name), a brand of pungent aged cheese that has matured for a longer period of time. It can be bitingly strong. It is often served in combination with sliced onion and aspic ("sky") on Danish "rugbrød" spread