Penicillium roqueforti, Penicillium gorgonzola or Penicillium glaucum spores are added to the cheese, which provide the blue-green colors and piquant flavor. The mold will not thrive until oxygen comes into contact with it, so the cheeses are pierced with pins, which allows the mold to flourish and causes the cheeses to develop a very high acid content and crumb-like texture.