Modern innovative technologies in the dairy industry allow to extend dairy products’ shelf life and to resolve urgent challenges of the competitive production of dairy products with the highest quality and the lowest cost. The domestic and international practice has accumulated experience and has the means to prolong the shelf life of products in the technological chain, providing minimal changes in their quality parameters [1, 2]. It is important to maintain a valuable set of consumer properties in food products, their high organoleptic properties and satisfactory appearance. The use of low temperatures is one of the practically available factors to inhibit the over-ripening of cheeses and the preservation of their quality. Storage efficiency is determined by how effectively it slows down the micro-biological, biochemical and physical-chemical processes in cheeses. The peculiarity of Russian cheese-making is that most companies produce semi-hard rennet cheeses with a low temperature second heating, mainly in the framework of the “low-cost” market segment. The most popular cheeses in the Russian market are “Rossyisky”, “Gollandsky”, “Poshehonsky”, etc. One of the factors limiting their consumption, is brief shelf life, generally not exceeding 3-4 months. Freezing is a solution for extension of the long-term storage of semi-hard rennet cheeses. The methods of refrigerated processing allow the creation of a long-term reserve of cheeses and to transform the supply system, thus solving the problem of preserving their quality and satisfying the needs of the Russian dairy market [2, 3, 4]. Storage at low positive temperatures does not not ensure the quality of the cheese during long-term preservation, because it does not sufficiently slow down the microbiological processes in dairy products. As of today, freezing is the best method in many respects and a promising way of extending the shelf life of food products. Ultra-low temperatures can significantly slow down the rate of the microbiological and biochemical processes that lead to product quality deterioration. Freezing has a number of benefits for the conservation of the original, natural properties of the product; it is also beneficial from an economic and energy consumption viewpoint. The low-temperature processing and storage ensure longer food preservation up to a year or more. The results of extensive use of low positive temperatures in the food technology have become the basis of studies on the effect of negative temperatures on possible qualitative changes in cheeses and their storage in the frozen conditions. Researchers’ opinions differ about it; however, the idea of long-term storage of ripened cheeses in frozen conditions prevails as the possibility of the recovery of their structure after thawing is satisfactory [1, 2]. A number of Russian scientists in the 30-50’s years of the twentieth century attempted to freeze semi-hard cheeses, but it had not become a basis for the development of the detailed methods and the technology of the low-temperature food storage. In some countries of the southern regions (Greece, Turkey, Italy, Spain) the research succeeded to develop the technology of the deep freezing and the storage of their traditional cheeses and curd made from cow, goat and sheep milk [3]. The analysis of the research on the rapid freezing and storage of frozen dairy products showed that the possibility of long-term storage of frozen semi-hard cheeses is least studied. A number of Russian researchers today (Moscow, Uglich) froze hard rennet cheese, and their research findings allowed them to infer the rational regime parameters of its freezing and thawing [6]. Kemerovo Institute of Food Science and Technology (University) has been conducting a study on the low-temperature storage of dairy products, in particular cheeses of different types, over the past 25 years. When freezing, the modes and methods of refrigerated treatment are crucial in preserving the original properties of the products. The phase transition of water into ice can damage the original internal structure of the cheese, and thus reduce its qualitative characteristics. The purpose of this study is to develop the theoretical foundations of the physical and chemical nature of the freezing of semi-hard rennet cheeses in order to increase their shelf life. OBJECTS AND METHODS OF STUDY We studied three main subclasses of semi-hard cheeses with a high, low-temperature second heating and cheddaring curd of a fat and semi-fat type, depending on the mass fraction of the fat in the dry matter. The geometrical dimensions met the standard to ripen cheeses of different shapes. To get finely packaged cheeses, we cut ripened cheese bars and heads into portions weighing 0.1-0.2 kg before testing. To study the freezing process, a test bench was set up, designed to change and to maintain the air temperature in the chamber to minus 100°C and a flow rate of 10 m/s. The monitoring of the temperature in the chamber, the tunnel and the tested samples during freezing was carried out according to the indications of the automatic electronic potentiometer (PCB-4 with a scale of 40 to -200°C, accuracy class 0.5). As the sensor, we used a Chromel-Copel thermocouple junction with a diameter of 0.3 × 10-3 m. The cheese samples were packaged in the plastic wraps and bags of a new generation of Cryovac VV3U type. The freezing was carried out at various ambient air conditions in the range -20 ... -50°C. The air velocity in the cooling zone was measured by a hot-wire anemometer (Testo 405-v1) with a measuring range of 0..15 m/s, and a scale of division of 0.1 m/s. The test samples were placed onto freezer shelves simulating a commercial freezer. The samples were frozen down from an initial temperature of 20°C to a pre-set volume-average temperature of -20°C and -12°C. Thermal images of the freezing were the main testing instruments during the heat-exchange experiments. They helped to determine the basic indicators of the process - the duration and the average freezing rate. The air temperature at 0 to -3°C in the refrigerator served as control storage conditions. We have been examining the quality of the tested samples before the freezing and during the refrigerated storage over 18 months with a sampling frequency of every 3 months. Prior to sampling, the samples were thawed out at a room temperature in air of 0 ... 3°C. To evaluate the properties of the original product at all stages of its low-temperature storage, we determined a set of quality indicators. We used the conventional and original research methods, including the physical-chemical, microbiological, biochemical and other methods. RESULTS AND DISCUSSION When considering the factors of product stability during its storage in a frozen form, it is necessary to single out the content and the properties of the protein fraction in cheeses, as the most significant component. A high proportion of milk protein in their composition (from 23 to 29%) leads to the high water absorption and water-binding properties of the curd [5]. The hydrophilic properties of the casein determine the steadiness of the protein particles to freezing. Unwanted loss of water upon freezing and during the storage can lead to protein aggregation at low temperatures. The water absorption properties affect the structural and mechanical characteristics of the product’s consistency; in this connection, the degree of hydration of the protein complex is one of the most important physical and chemical factors in assessing the impact of the cold on the frozen product. Low protein hydration is one of the causes of the texture’s defects: not elastic enough, crumbly, powdery [5]. For frozen products, the preservation of the degree of the hydration of the curd and consequently, of its satisfactory texture, is a matter of paramount importance. The amount of bound water is a criterion of the changes in the cheese protein complex. The polar groups of the protein molecules -COOH, -OH, >CO-NH