Holes

During ripening, the carbon dioxide (CO₂) produced by the cultures cannot escape from the curd or rind, creating cavities—the fermentation holes that characterize many of our aged varieties. These fermentation holes in mountain cheese, for example, are distinct from the slit or curd holes found in Tilsiter, which arise intentionally when the curd is placed in moulds without whey.
For the production of large-hole cheeses such as Emmentaler, specific bacteria (propionic acid bacteria) are added to the milk; at temperatures of 20 to 24 °C during the first few weeks of maturation, these bacteria cause the formation of the holes typical of these cheese varieties.