Piercing
Pushing steel needles through a young blue cheese so that air can reach inside and the blue mould can grow.
Also: needling, spiking, piquage
Blue mould needs air. A young blue cheese is made from loose, open curd that already has small gaps, but its rind soon closes, so after a few weeks the cheesemaker pierces it from top to bottom, or side to side, with long stainless steel needles, sometimes by hand and often by a machine with dozens of spikes. Oxygen enters along the channels, and Penicillium roqueforti grows outward from them into veins. On a cut Stilton or Gorgonzola you can often see the straight lines left by the needles, with the blue strongest along them. Some cheeses are pierced more than once. Without piercing, a blue cheese stays mostly white.