How do the holes get into cheese?

How do the holes get into cheese?

 Cheese is made by adding rennet - a combination of various enzymes - to milk so that it coagulates, In the process, some of the protein and fat turn to 'curds' which separate from the res called 'whey' . The surds are then pressed into moulds and stored for a time until they mature.

In some cheeses, such as Tilsit, irregular holes appear because the curds are poured loosely into mould and not pressed. More whey drains away during storage, leaving cavities in the cheese. Large, spherical holes like those in Emmental - known as 'Swiss' cheese in some countries - develop a firm rind. The holes are produced by the lactic acid bacteria present in raw, unpasteurised milk. To make cheese with particularly large holes requires the addition of propionic acid bacteria, which consume the lactose and produce carbon dioxide as the cheese matures. The small bubbles join with larger ones, and as the rind develops and the curds harden, they are unable to escape. The holes vary in size according to how the cheese is matured and the number of bacteria present.

Why are mouldy cheeses mouldy?

Cheese like Stilton or Camembert are injected with harmless, edible, mould cultures under the most stringent hygienic conditions. Once the mould has spread, there is no room left in the cheese for any harrmful alien moulds. If cut cheese is left uneaten for a while the 'good' mould can grow over the cut surface or spread to other types of cheese stored nearby.