Throughout the less upmarket areas of shopping and feeding-out, "blue cheese" almost invariably means "Danish Blue". It, by itself, is generally on the shelf in small corner stores. It is on the cheese board along with Cheddar perhaps in the lowlier restaurants.
This is tragic, because, whilst Stilton, blue Shropshire, blue Cheshire, blue Vinney, Gorgonzola, Roquefort and such modern inventions as Cambazola and many others, are delicious, Danish Blue is ghastly! It tastes, most people assert, of copper sulphate, sulphide etc. – probably with just a touch of lead and antimony to make it supreme.
We are told that Danish Blue is made by having copper wires passed through the cheese as it matures. We are also told, however, that this is an urban myth, the 'blueness' of Danish Blue is brought about by Penicillium roqueforti.
There is, however, both truth and falsity in this assertion, and what actually happened, and is perpetuated in its manufacture, is this. In all these blue cheeses the fungal or bacterial cult is inserted into the cream by rods whilst it is beginning to thicken. In some cheeses the culture is found there automatically in the milk or the surroundings (a cave at Roquefort, for example.) The treatment by rods, however, ensures a more homogeneous presence throughout the mold. Note that the French fromage comes by metathesis from formage (as in Forme D'Anvers), which refers to the mold or form in which the cheese is made.
Originally wooden rods were used in this process, but they easily rotted, pieces broke off, and the result was unpleasant. Some experimented with early varieties of stainless steel, the makers of Danish Blue tried copper. One day the copper rods were left in a little too long through negligence or error. When the resultant cheese came to be tasted, the manufacturer said "Yum!" Rather than admitting the fault, he proclaimed its especial quality, and we are left with a blue cheese tasting primarily of cyprianic metal rather than penicillium roqueforti.
There is a considerable parallel here with the production of the Greek wine Retzina. It is said in the guide books and by the culinary specialists that the resin is added to the wine in order to preserve it. This is a nonsense for the alcohol content of wine gives the preservation. Much like in the production of Danish Blue, what happened was this. The barrels in which the Greek wine was stored were, of course, made of oak. One day, however, when there was a major order for barrels, the cooper was out of oak and couldn't find any, so he used pine, of which there was plenty around. When the wine in its maturity was broached what one had was, of course, Retzina. "Yum", said not only the vintner but all his customers, and from that moment onwards resin was added to the wine so as to produce that effect whether the barrels had gone back to being oak or not. Even those who do not like the flavour of resin pretend to ethnicity and buy it for their friends when putting on a barbecue. It actually needs very hot weather to be fully appreciated. God knows what Danish Blue needs to make it palatable.