Ripening is the last technological stage of cheese-making, coming after salting. A complex process, it results from the action of enzymes, both those found in the milk and curd, and those secreted by microorganisms that grow spontaneously in the milk or are seeded through the use of pure cultures and leavenings.
The cheese paste starts the ripening process porcelain-white, crumbly and tasteless, before becoming yellowy-white, elastic, oily, and taking on its specific taste and aroma. The changes that take place during ripening happen in a certain order, and are caused by the main components of milk: lactose, proteins and fats.
Stages of the ripening process
- during prematuration (preliminary fermentation), the cheese paste undergoes acidification, due largely to lactic streptococci. For semi-hard cheeses, the formation of individual holes also begins;
- the actual maturation (main fermentation) caused mainly by lactobacilli, which act to a lesser extent as acidifiers. This stage involves intense proteolytic action, and proteins are broken down into polypeptides and amino acids, sometimes even resulting in ammonia. The production of flavours also begins. The "eyes" that give hard cheeses their characteristic pattern are also formed.
- during final maturation (final fermentation) the lactic microflora continue to have an effect, but they are joined by other specific microorganisms. This stage sees the product's taste and aroma reach completion.
Cheese ripening involves two main transformations:
1. Decomposition of lactose as lactic fermentation breaks down into lactic acid.
The role of the lactic acid formed at the start of ripening:
- lactic acid regulates the development of the microorganisms in cheese: it inhibits the microflora that rot and produce gas, boosting the development of acid-consuming microorganisms;
- lactic acid influences the structure and consistency of the paste, making it fine, soft and yellowish, based on the type of cheese; lactic acid is a component of flavour, directly or through substances that may arise from the transformation of lactates.
2. Fat breakdown - lipolysis that leads to the formation of glycerine and the appearance of free fatty acids, which can then undergo various transformations, eventually resulting in ketones.
Qualitative changes during maturation
The reduction of humidity depends on the duration and temperature conditions in the ripening chamber. Meanwhile, the rind, characteristic of each assortment, reaches completion.
Variations to the consistency of the cheese are the main change.
Under the action of proteolytic enzymes that hydrolyze the casein protein and after the breakdown of lactic acid, the cheese paste loses its elasticity and becomes more plastic.
The formation of the cheese's characteristic pattern is due to the production and accumulation of carbon dioxide.
The formation of "eyes" is characteristic of Emmental cheeses, brought about by several factors: temperature, pH, paste consistency, salt content.
Taste and aroma substances are formed in the final phase of ripening.
In small quantities, lactic acid gives cheeses a pleasantly sour taste. In hard and semi-hard cheeses, the sour taste gradually disappears after the breakdown of lactic acid and is replaced by a taste similar to that of walnut kernels.
The salt highlights the individual tastes and flavors.
The fat loosens the cheese paste and has an emulsifying effect.
Protein hydrolysis products shape the cheese's taste and aroma. The greater the decomposition, the more intense the taste. With extra mature cheeses, especially those with bacterial flora on the rind, amines and ammonia determine the taste and smell.
Taste and aroma depend not only on the presence of certain components formed through ripening, but also require a balanced mixture of substances resulting from the transformation of casein, lactose and fat.
If mistakes in ripening change the composition of this mixture, the cheese won't taste right.
Microclimate in the ripening room
Cheeses are placed on fixed or movable shelves in the ripening chamber.
The fixed shelves are made of softwood, precast concrete, metal (painted iron, stainless steel, aluminium) or plastic. Movable softwood boards, on which the pieces of cheese are placed, are attached to the shelves.
The distance between the shelves varies depending on the type of cheese, to faciliatate air circulation.
Individual cheese varieties require a specific temperature and relative air humidity in the ripening chamber.
A high temperature promotes microorganism multiplication and activity, and a low temperature vice versa, delaying ripening. In general, cheeses ripen at temperatures of 10-20°C. Some cheeses (e.g. Swiss) mature briefly above 20°C, while others obtain their characteristic taste and aroma below 10°C (Roquefort).
The main fermentation processes take place in chambers with temperatures of 15-20°C for small-format cheeses and 20-26°C for large-format cheeses.
Cheeses are moved from the warm ripening chambers, where they obtain their requisite design and begin to form their specific consistency, taste and aroma, to cold chambers, kept at 10-14°C, where the ripening process is completed.
Once fully ripened, cheeses are put in cold storage where they are kept at a temperature of -3°C or above.
Relative air humidity
High humidity is required to ensure the development of specific molds on the rind or inside the cheese, determining the quality and characteristics of some varieties (Brie, Camembert). Low humidity in the ripening chamber can over-dehydrate the cheese, greatly reducing its weight.
In the first phase of ripening, humidity must be high to facilitate salt penetration, for a uniform salting. During the main ripening period, humidity must be as low as possible to prevent the development of mold on the cheese's surface.
The ripening chamber must also be adequately ventilated, with fresh air daily, and in some cases even 3-4 times a day. Natural or artificial ventilation may be used for this purpose.
Active ventilation is required when cheese is being turned, especially after it is removed from the brine. Lower ventilation is recommended for blue and soft cheeses.
Different cheeses require different special treatment during ripening.
Salting, dry wiping, scraping
For hard cheeses, sprinkle salt on the surface, then brush it in. Periodically wash the cheese with salt water, and scrape the rind if it is too thick.
Semi-hard cheeses are washed with a low-concentration brine, made with lukewarm water or lime water, which promotes a good quality yellow rind. With soft blue cheeses, the surface treatment involves spreading the mold and perhaps washing with brine. For interior-mold cheeses, such as Roquefort, the surface can be cleaned by scraping.
Cheeses that mature without the action of red-producing bacteria (Bacterium linens) are periodically washed with lukewarm water, and interior and surface mold removed with a soft brush. Cheese-brushing machines can also be used, achieving higher productivity.
Turning stops the cheese becoming misshapen, ensuring uniform salting and ripening. Cheeses are usually turned manually, but in high-tech factories, mechanically.
To prevent infection of the rind, shelves must be washed with hot water and disinfected with lime water mixed with lime chloride. During the treatment, cheeses are moved around on the shelves and in the ripening chamber, as necessary. Raw cheeses are placed in the warmer parts of the chamber (on upper shelves or near heaters), and those that mature in colder temperatures, on the lower shelves.