Generally speaking, the aversion from mold in foods comes from the cognition that mold on fresh foods clearly indicates that they are no longer fresh. We also assume that food would not taste the same because a fermentation has began to take place -usually accompanied by change in appearance, texture and aroma of the food in question. Many molds simply taste unpleasant yet are not problematic to our bodies. Dangerous moulds are those which produce mycotoxins and aflatoxins. These toxins may effect our respiratory system and in some cases even act as carcinogens. Not all molds produce these toxins.
Penicillium Roqueforti and Penicillium Glaucum which are the blue molds used for cheese, cannot produce these toxins in cheese. The combination of acidity, salinity, moisture, density, temperature and oxygen flow creates an environment that is far outside the envelope of toxin production range for these molds. In fact, this is true for almost all molds in cheese, which is the reason that cheese has been considered a safe moldy food to eat over the past 9,000 years. Not only is it safe but it can also be healthy (P.Roqueforti and P.Glaucum have natural antibacterial properties and ability to over-take pathogens. Moreover, our bodies use a variety of wild flora for digestion, development and immune systems).
Unfortunately, mass food manufacturers have run relentless campaigns over the previous few generations to cause consumers to conclude (beyond their 9,000 years of wisdom) that plasticy looking bright-colored food-like substances with homogenous texture, in a vacuum-pack and big brand logo = equals controlled/safe product. Anything moldy, rustic, irregular, inconsistent or natural = equals unsanitary conditions, primitive family farming, or uncontrolled production. Today we understand that this is not the case as we go back to traditional and artisan foods -and stay away from highly processed industrial food replacements.
Blue Molds - have a particularly unique effect on cheese. They accelerate two processes dramatically: Proteolysis (breakdown of proteins), which causes the cheese to take on extra-creamy texture (especially in proximity to the blue mold veins), and lipolysis (breakdown of fats), which makes up the tangy, spicy, sharp and strong flavor. The creamy texture stand up to the sharp flavor and together they bring upon an exciting flavor/texture/aroma profile, which is often further balanced against sweet/nutty milk and lots of salt (Blue cheeses typically contain twice the salt of other cheeses). This combination is so unique - it is unlike any other food!
Before going into the second part of the question ("can one "bleu-ify" other cheeses at home?") let's just understand the process in a nutshell:
Blue mold grows only during a specific time frame within the aging period. It needs a balanced acidity, so it can't grow on the cheese if is too young and still acidic. It also relies on nutrients which are still readily available in the cheese -so it can't be too late when the cheese is already aged.
The mold spores are highly contagious to other cheeses so blue cheeses typically would not share aging space with other cheeses during this sensitive period.
The cheese is usually pierced with a thick needle first so that oxygen will flow into its crevices and kickstart the growth. The cheesemaker would repeat this process every 7-14 days until sufficient growth of blue has taken place.
At this point, the cheese is wrapped in foil to prevent the blue from growing out of control. The cheese is then immediately moved to cooler temperature and aged for the remaining period, allowing the processes of proteolysis and lipolysis to take place and develop deep and complex texture, flavor and aroma. In some cases this last stage could take up several months past the development and stoppage of the blue mold.
Bluing Cheese at Home:
Trying to blue an unsuspecting cheese at home may prove difficult. The cheese you purchase is often already aged, ripe and stable. It lacks sufficiant nutrients to support the growth of new blue mold. Competition from other well-established molds and yeasts in the rind may be too much for the blue to overcome at such late stage.
Having said that, this is not an impossible experiment. One just needs to find a cheese that is very young and has little or no rind. It must be moist enough to support the growth of this mold, yet it firm enough to enable the puncture a hole through it with a knitting needle. To "blue" it, one would need blue mold (can be purchased or scraped off moldy rye bread or another blue cheese, or simply pulverize a piece of blue cheese in a blender with a little bit of water and a pinch of salt). The procedure would be to sanitize a knitting needle or metal skewer and dip it in the mold to "contaminate" it with blue. Use it to pierce the cheese through from both ends to assure ample mold seeding and clear air passages. Set the cheese on its side so air can flow through it. It is best to start it at about 55°F or 13°C (temperature of a wine cooler) with high humidity (90%-95%). When the growth of blue is sufficient (1-3 weeks) wrap with foil and move to the fridge for a few more weeks or months. In theory this should work but blue cheese are finicky and tricky to get right. Many variables may still fail it.
Above: Blue Stilton cheese is being pierced manually. In a more industrial settings, a piercing machine is used for fast piercing at perfect angle and distance
Above: Young Roquefort cheese in the Roquefort sur Soulzon caves, are resting on their side to enable the flow of moist air into its holes and piercings -so the blue mold begins to take hold. One can see early blue spotting developing on these.
Above: Roquefort cheese is being wrapped in foil to stop the growth of blue before it takes over.
Above: Rye bread left in the cheese caves of Roquefort sur Soulzon to mold and help the nearby cheese develop by releasing spores into the air
Above: The perfectly straight 90° lines of blue mold in this Gorgonzola cheese are not accidental; these are the traces of where needles were used to pierce it.