blue cheeses owe their flavour and appearance to a blue mould, usually Penicillium roqueforti or P. glaucum. Some of the finest blue cheeses, such as Roquefort, continued until recent times to be of ‘natural’ formation in the sense that they picked up their special moulds from their surroundings; but virtually all blue cheeses are now deliberately inoculated with the chosen mould, so that their development is fully under control. In the larger and harder blue cheeses, the mould is encouraged to penetrate throughout by stabbing the cheese with copper needles which carry mould spores to the interior. Even the hardest blue cheeses have a fairly open-textured curd which allows mould to grow between the granules, giving a marbled appearance to a slice of the cheese.
