The production of traditional yogurt, brined white cheese, and yellow cheese, called “kashkaval”, in the Bulgarian region determines its daily consumption and health benefits for the local population. Artisanal dairy products and their indigenous microbiota are a promising source for research and creation of new minimally processed, but safe, functional, and tasty foods. Lactobacillus strains are used in various fermentation technologies and improve the structure, taste, and aroma of the final products. These products have a long shelf life due to the biopreservative capabilities of lactic acid bacteria (LAB) strains, their positive impact on health, and many physiological functions in the body.
Overview of traditional Bulgarian dairy products: appearance, nutritional value, production technologies, and shelf life
Katak
Katak or kotmach is a typical Bulgarian salty-tasting dairy product. The name is used for several products with similar taste but different recipes. Traditionally, katak is obtained by inoculating sheep’s milk with cheese used as a starter culture. The resulting product is durable and can be stored for several months. Katak can be made from boiled or non-boiled milk, but the former is significantly tastier. To obtain a thicker product, the sheep’s milk must be boiled over low heat for several hours (or days) before inoculation. The ancient technology is described in an ethnographic study as follows: The starting material must be sheep’s milk, collected in August, when the milk is relatively thick, and thickened by boiling in a water bath (in a small container immersed in a larger container of water). The milk is boiled continuously, sometimes stirred with a wooden spoon, for several hours until it reaches the desired creamy consistency. After cooling, white brined cheese (as a starter culture) and a little salt are added.
In the past, it was usually stored in thoroughly washed sheepskin; the remaining liquid is released through the pores of the skin, which makes the katak tastier. It can then be stored in glass or plastic jars in a cool place. Today, katak is often a homogeneous mixture of yogurt and sheep cheese, to which butter may also be added. However, this is not an authentic product. Due to its salt content, katak organoleptically has a taste that is a cross between yogurt and soft ripened cheese. It contains less fat (10%) than cheese and (1%) carbohydrates. Its shelf life is over 12 months.
Koumiss
Koumiss is a traditional dairy drink in Central Asia, China, Russia, and Kazakhstan, and is known as airag, the national drink of Mongolia. The technology for its production was most likely brought to Europe by the Bulgarians around the 7th century. Koumiss is usually produced by fermenting raw milk with indigenous lactic acid bacteria and yeast. Similar to the kefir, it is a slightly alcoholic, lactic acid-rich beverage, but it is prepared by a liquid starter of the previous day batch inoculated to fresh milk and kept for about 8h of fermentation. However, unlike kefir, which can be made from any known type of milk, koumiss is made only from mare’s and camel’s milk, which are high in sugar (6.3% lactose) and low in fat (12.1%).
Today, mass production of koumiss is done from cow’s milk with the addition of sugar to achieve the composition of mare’s milk. After fermentation, koumiss typically contains about 2% alcohol, 0.5 to 1.5% lactic acid, 2 to 4% sugar, and 2% fat. Depending on the amount of lactic acid and ethanol, koumiss is classified as mild, medium, and strong in flavor.
Rhodope’s Brano Mliako
Brano Meliako, almost forgotten today, has been a traditional dairy product in the Rhodope Mountains since ancient times. This original Rhodope dairy product, recognized for its properties as one of the most unique organic foods in the world, is prepared according to an ancient recipe that has remained unchanged for centuries. Brano Meliako is similar to yogurt, but is made only at the end of summer from ewe’s milk. The raw milk is collected for several days in special wooden containers, where it is filtered and concentrated by significant dehydration. The concentrated milk is fermented spontaneously, or supplemented with a small amount of starter culture (sheep’s yogurt) and then “sealed” with a thin layer of sheep or goat fat.
Brano Meliako is suitable for use for the next three or four months with its taste fully preserved. A laboratory method developed by Grove (1970) obtained the same product and described its technology. It involves doubling the concentration of milk at reduced pressure (45-50°C), sterilizing by the Koch method for 30 minutes; cooling to 45°C, adding 1% yogurt starter, fermenting to an acidity of about 190°T acidity ; adding 2% yeast starter, isolated from brano miliaco (cultured in grape must), fermenting; filling into glass containers at the end of yeast fermentation, sealing tightly and storing at 8-10°C for at least four months. Whether produced by traditional or laboratory methods, brano miliaco is popular among scientists looking for reasons for the longevity of the peasant population in the Rhodope Mountains.
Kashkaval (yellow cheese)
Kashkaval is also a hard cheese and is considered a typical yellow cheese in Bulgaria. Yellow cheese is a dairy product produced mainly in the Balkan Peninsula and the Mediterranean. According to the Bulgarian National Standard, Kashkaval is made from different types of milk. When made from sheep’s milk, it is called “Balkan”, when made from cow’s milk, it is called “Vitosha”, and when made from a mixture of two types of milk, it is called “Preslav”. To develop its specific and special aroma, it is aged for 2 to 6 months.
Homemade Kashkaval is made from milk with a minimum fat content of 3.5% and without any additives. In short, the technology involves pre-filtering and centrifuging raw milk and heating it at 60-63°C for 20 seconds to reduce the number of spoilage microflora and, at the same time, to preserve beneficial LAB bacteria. The milk is then cooled and rennet is added, and curdling occurs in 30 to 40 minutes. The curd is cut into small pieces of 0.5 cm in size, and the whey is released. After a while, the whole mass is stirred for about 20 minutes, then heated to a temperature of 38 to 39°C with constant stirring. This method is called “cheese cooking”. With industrial recipes, the cheese can be boiled at this stage by adding weak acids such as citrate or acetate. When finished, the grains become firm and elastic, and the whey is separated. The cheddaring process begins. This process takes 2 to 3 hours at 35 to 37°C and, due to the rapid lactic acid fermentation, causes:
(1) the proliferation of LAB, which breaks down lactose into lactic acid,
(2) a decrease in pH to 4.5 to 5.2,
and (3) the extraction of calcium from calcium paracaseinate to obtain monocalcium paracaseinate, a soft and flexible material that allows for easy compression and shaping of the final product. Thus, Kashkaval acquires plastic properties and is considered ready when it emits a drum-like sound when tapped. The cheese is then cut into thin slices and placed in a concentrated salt solution, which helps to remove water and increase firmness. Finally, it is boiled for a few minutes, and the resulting aqueous solution is kneaded and placed in molds. After a day, it is removed from the mold and left to ripen for 55 days at a temperature of about 8 to 12°C.
After ripening, the cheese can be covered with paraffin or immersed in melted wax to prevent it from drying out. The lactic acid bacteria in the starter ultimately determine the flavor of the cheese during its ripening, which is a slow and expensive process that requires special chambers that allow for proper temperature and humidity control. During 12 months of storage, in four different temperature regimes (4, 1, -7.5, and -18°C), the main physicochemical parameters of cow’s milk cheese, namely water content, dry matter, total protein, total fat and salt, do not change significantly.
The ratio of water-soluble nitrogen to total nitrogen is significantly affected by the storage temperature. Higher temperatures allow for longer glycolysis and proteolysis in the cheese. Data on the viable bacterial content of the product showed a greater sensitivity to the effect of low temperatures on Lactobacillus species compared to Streptococcus species. They reported a one-log reduction in viable lactobacilli after 12 months of refrigerated (-7°C) and frozen (-18°C) storage, while viable cell counts of Streptococcus species remained unchanged.
Conclusion
The beneficial effects of dairy consumption can be attributed to the biologically active compounds present in these products; to the modification of milk components by starter cultures; and, most importantly, to the direct consumption of LAB strains as preventive and therapeutic agents. This beneficial effect may be direct, through the interaction of the human body with the consumed microorganisms, or indirect, as a result of microbial metabolites produced during the fermentation process. The development of new dairy products should be based on current knowledge of the food-gut axis as well as new and rigorous experiments to reveal the mechanisms by which their metabolites can influence health problems.
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