Blue or blue-veined cheeses are made from cow's, sheep's or goat's milk. They have this "marbled" aspect because of the development of Penicillium roqueforti or glaucum. There are two categories of blue cheese: strong blue cheeses like Roquefort and mild blue cheeses like Gorgonzola. Some have obtained the PDO designation. They are produced in the same way as the others. The only differentiation is during the coagulation process, they are sown with a microscopic fungus. It is this fungus that produces the bluish moulds that can be seen on the cheese, and which gives it its marbled appearance.
