**1.2 Traditional cheese**

• *White-brined cheese:* After yoghurt, the second most widespread and consumed dairy product in Bulgaria is white-brined cheese. It is prepared from cow, goat, sheep, and buffalo milk as well as from mixed milk. Cheese made from a mixture of different types of milk usually possesses improved nutritional value [10]. The production technology of white-brined cheese is specific and involves fermentation and storage in brine (**Figure 2**).

Traditionally at the beginning of the process, the raw milk is preheated, cooled, and fermented by using an enzyme mixture that curdles the casein in the milk, called rennet. Rennet contains the endopeptidases pepsin, lipase, and chymosin [11]. It is originally isolated from the abomasum of new-born ruminants but in industrial processes is mainly biotechnologically obtained by fermentation with recombinant microorganisms, including *Escherichia coli*, *Kluyveromyces lactis,* or *Aspergillus niger* var*. awamori* [12]. Then, the coagulate must be strained in order to separate the aqueous phase from the solid matter. The cheese is later put to ripen for at least 45 days at 15°C, a lengthy process of intensive acidification, lipolysis, and proteolysis. After that,

**Figure 2.**

*Scheme of artisanal and industrial technology of Bulgarian white-brined cheese production.*

#### *From Traditional Bulgarian Dairy Products to Functional Foods DOI: http://dx.doi.org/10.5772/intechopen.108998*

the product is salted and packaged in containers with brine. The brine should comprise 6–10% sodium chloride, and the acidity of the final product must be 160–180°T. The shelf life of the white-brined cheese is 12–18 months. The final product is a hard cheese with low water and high solid content. Its quality is determined by microbiological, physical, and chemical characteristics and evaluated by its organoleptic qualities, which guarantee the safety, prolonged shelf life, and high nutritional value of the product. The high energy and nutrition of the cheese are mostly due to the high fat and protein content as well as easily digestible peptides; essential free amino acids; minerals, including zinc, magnesium, phosphorus, and calcium; and vitamins, including vitamin A, B, E, and D [13].

• "*Kashkaval*" is the most widespread yellow cheese in Bulgaria and is also from the group of semi-hard cheese. This dairy product can also be made from various kinds of milk, like cow, sheep, goat, and mixed milk, according to the National Bulgarian Standard 14:2010. The production technology of "*Kashkaval*" involves a mandatory cheddarization process, which takes a period of 2 to 6 months for the final product to develop its characteristic aroma. The technology starts with the filtering and centrifugation of raw milk. The milk is then heated to 60–63°C for 20 s to decrease the number of potential spoilage microorganisms and at the same time to preserve the LAB strains. After that, it is cooled and poured into a large vessel, then rennet is added, and the curdling process takes place for 30–40 min. The coagulated mass is cut into small pieces so that the whey can be easily released and stirred for 20 min, followed by another stirring process at 38–39°C, the so-called "cheese baking" process. In some artisanal technologies, weak acids, like acetic acid or citric acid, can be added at this stage to "boil" the cheese. This step is completed when the cheese grains become hard but elastic. The whey is then drained, and the cheddarization takes place at 35–37°C for 2–3 h. Upon this process, a rapid lactic acid fermentation starts, where LAB transform lactose to lactic acid, the pH decreases to 5.2–5.4, and calcium P-caseinate breaks down to monocalcium P-caseinate, achieving a soft and easy-to-manipulate final product. Before getting ready for the next stage, the cheese needs to harden for some time. Then, it is cut into thin slices and placed in a concentrated saline solution for water to be removed and for the cheese to become more firm. Further, the cheese is boiled to obtain a slurry consistency, which is then kneaded and placed in vessels. On the next day, the product is separated from the vessels and left to ripen at 8–12°C for around 55 days. Ultimately, to prevent it from drying out, the ripened "*Kashkaval*" can be covered with melted wax or paraffin. The LAB starter culture determines the specific taste of the final product [14].

Different "*Kashkaval*" products are being made across Bulgaria, and all are in the group of semi-hard cheese. The hardness, texture, flavor, and aroma of the final products depend on the moisture and the aging period. The quality during storage can be evaluated by physical parameters, such as water content, dry matter, total fat content, total protein content, and total salt content [15].
