Moulds and bacteria help to give cheeses their special flavor.
Normally, we try to stop molds and bacteria forming on food. But many molds and bacteria are quite harmless and it is some of these harmless ones that give certain cheeses their distinctive taste. For example, Swiss cheeses often have holes in them. The holes are caused by gases given off by bacteria that are introduced on purpose into the cheese while it is maturing. Another special mold produces the blue veins in Roquefort cheese from France. Camembert, also from France, has a greyish-white mold growing on its surface, which many consider the most delicious part of the whole cheese.