Milk’s fermentation can be natural, when bacteria cultures sour the milk after being left in a warm place. This is how for example homemade cottage cheese is prepared. Cheesemakers call this kind of fermentation “spontaneous.” In today’s dairying the process is controlled – inocula containing selected bacteria cultures are added to the milk. Thanks to that, it is possible to prevent the fermentation from going in an unwanted direction, which affects both the texture, and the taste of the cheese. Adding some special enzymes which turn the milk into a so-called curd (a slightly gelatinous substance) is another, similar way of processing milk. The cheesemaking jargon calls the enzymes rennet. Natural rennin can be an animal product acquired from the stomachs of various animals (calves, lambs, goats or even pigs) or a vegetable product – e.g. sheep's milk cheeses are produced with artichoke rennin. Vegetable rennet is used on a large scale for the cheeses made for vegetarians. At present, synthetic rennet with the properties of the animal ones are used. Synthetic rennet is developed based on a chemical combination of different elements and compounds. All kinds of rennet are available either in the form of powder or frozen liquid which is added to the milk after the cheesemaker prepares them.
The gel which is created by rennet is cut and shredded. In the case of Old Poland cheeses, curd is shredded into little pieces, similar to grains of cereal or rice. The shredding helps drip the whey, gives the cheese the right consistency during ripening and makes it possible to mould the cheese into desired shapes like rounds or blocks etc. Pressing cheese is an extremely important element as it allows for draining the rest of the whey. The formed and drained cheese block undergoes salting. Depending on the kind of cheese it can be either done by hand, by putting salt on every side of the block for a few consecutive days. Immersing cheese in a specially prepared brine for a day or more is another solution. The time cheese spends in brine depends on the size of the round or other form.
After salting, the time for ripening and tending to the cheese comes. Tending to the cheese in the first days of its “life” is especially laborious. The cheeses are laid on wooden boards (different kinds of wood are used for different kinds of cheese). They should also be rotated with proper frequency (the French Roquefort needs it 5-6 times per day). Apart from human work, the temperature and humidity in the rooms as well as the bacterial micro flora suitable for a particular kind of cheese have a very important role during the ripening. In nature, such conditions may be found in caves. Many French cheese producers adapted abandoned railway tunnels for ripening rooms. Certain kinds of cheese, like Pecorino do Fossa, mature buried a few meters underground.
During ripening, cheese often changes its structure and loses large amounts of water. When maturing is longer, special amino acids resembling little crystals appear. An even distribution of amino acids in cheeses with a long maturing period is one of the main characteristics of a good cheese and proof of exceptional cheesemaking skills. Some kinds of cheese may mature in a ripening room even for a few years. However, just as in the case of wines, cheeses cannot mature forever, as with the passage of time they lose many fresh aromas.
In modern, industrial ripening rooms, the naturally forming rind is covered in the so-called polyacetate water dispersion (by immersing cheese in a liquid or rubbing the surface of the cheese with a sponge). As a result, a breathable rind is formed on the surface of the cheese, which allows it to breathe and mature properly. Additionally, the polyacetates work as fungicides that kill mould.