*2.1. Milk Industry and Actual Problems*

It is known that milk and dairy products belong to the group of products of daily consumption and accompany a person throughout his life; many studies have been done and published on the effect of milk on human health [4–8]. The world market is mainly represented by such types of milk as cow, buffalo, goat, sheep, and camel. The dynamics of the annual increase in milk yield is shown in Figure 1a.

**Figure 1.** Production of all types of milk according OECD-FAO Agricultural Outlook [9] (**a**) and relevance of milk tests (**b**).

The annual consumption of dairy products in Russia reaches 16% of all types of food [7]. In the conditions of the current deficiency of animal protein, it is imperative to include dairy products in the diet. According to the Ministry of Health, the rate of consumption of milk and dairy products per person in Russia is 325 kg per year [7]. However, according to Rosstat reports, Russians receive less than 30%. So in 2018, Russians consumed less than 230 kg of dairy products, and in 2019—229 kg. In China, according to the «Dietary Guidelines for Chinese Residents», the daily consumption of milk and dairy products should be 300 g per day or 109.5 kg per year. But according to IFCN, the average is only 31 kg per capita per year (or 85 g per day). The low level of consumption of dairy products is due to cultural and historical features. In India, the recommended rate is the same as in China, 109.5 kg per year, while the real consumption exceeds the nominal and averages 131 kg per year. European countries have a high level of consumption of dairy products. The average is 306 kg per year. According to the recommendations of the German Society for Healthy Nutrition (DGE, Deutsche Gesellschaft für Ernährung), it is recommended to consume 200–250 g of milk and low-fat dairy products daily, 2 slices of low-fat cheese (50–60 g), i.e., about 91–113 kg of milk per per capita year. According to the «2015–2020 Dietary Guidelines for Americans» [6], developed in the United States and used as a guide in some countries, the recommended level of dairy consumption for children aged 9–18 and adults is about 3 "cup-equivalents," that is about 1137.7 g per day or 415 kg per year. The real indicator of consumption of milk and dairy products in 2015 in the United States was 269 kg per capita per year. According to The DairyNews, citing Dairy Repoter, Switzerland also does not consume enough dairy products. Thus, the annual consumption of milk per inhabitant has decreased over 20 years from 79 to 53.3 kg.

In general, an important problem in the world remains the lack of raw milk and the deficit in both total volume and quality. The reasons for this situation are multifaceted—there is a decrease in the total livestock population, production of low-quality products, insufficient breeding work, outdated methods of keeping and feeding animals, outdated and worn out equipment, a shortage of personnel (both highly qualified and working personnel), unpopularity of the profession, low prices for raw milk, low investment attractiveness (the dairy industry is traditionally an industry with a low payback level), long payback periods.

Currently, an urgent problem in dairy farming is to ensure the quality and safety of raw milk as the main raw material for dairy products. Quality management should be considered as a purposeful process of coordinated actions in the system of the dairy complex of the agro-industrial complex to establish, ensure, and maintain the required quality level of marketable products that meets the requirements of customers and processing enterprises. Quality is the fundamental factor that makes up competitiveness. This also applies to agricultural producers, whose products must compete successfully in a free market economy. Competent assessment of raw milk allows to prevent and reduce losses, increase sales income.

Milk has a short shelf life. Its quality directly depends on the fulfillment of conditions at all stages of production: from collection at the farm level, transportation, acceptance, and processing at the dairy. Therefore, sampling and analysis must be carried out throughout the milk processing line. Modern industrial processing based on high-tech processes makes high demands on the quality of milk used as raw material for the production of a wide range of dairy products (Figure 1b).

Some large producers make their requirements for raw materials, which are often quite strict in terms of protein, fat, and somatic cells content, while reducing the purchase prices for milk of a lower grade. The solution to improve the quality and reduce the cost of equipment can be new efficient and inexpensive technologies that would allow assessing the quality of milk produced. The problems faced by the agricultural producer are the ingress of low-quality raw milk into the general flow (milk pipeline, cooling tanker). For example, milk from cows with mastitis (open or closed form), contamination of raw materials with microorganisms from an insufficiently treated udder of a cow, poor-quality disinfection of dairy equipment, etc. In this case, the raw material becomes either unsuitable for further use and processing, or its grade decreases, and as a consequence, the purchase price decreases. Dairies cannot produce a quality product from such raw materials, and farms suffer significant losses.

Another important question is the composition of milk. Its chemical composition not only determines its nutritional and biological value, but also affects the technological processing, yield, and quality of finished products [10,11]. The content of individual components in milk is not constant; it changes depending on the stage of lactation, breed, and health status of animals [12], quality of feed, season, age, individual characteristics, conditions of maintenance, milking technique, etc. [13,14]. During processing and production of products, milk is subjected to mechanical, thermal, and chemical treatments that change its characteristics, which affects the technological processes and properties of the final product [10,11,15]. If the raw milk does not meet the necessary requirements, then the final product will be of inadequate quality. Therefore, it is very important that already at the farm level it is possible to determine the composition of milk from each group of cows. This will allow adjusting the ration of the dairy herd and culling the livestock in time.

#### *2.2. Milk Composition and Main Parameters*

The main indicators that characterize the quality of milk are: chemical composition, degree of purity, organoleptic, biochemical, physical and mechanical properties, as well as the presence of toxic and neutralizing substances in it.

Milk contains more than a hundred organic (fat, proteins, carbohydrates, enzymes, vitamins, hormones) and inorganic (water, mineral salts, pigments, gases) substances [16]. Milk consists of water and food substances distributed in it-fats, proteins, carbohydrates, enzymes, vitamins, minerals, gases [17] (Figure 2).

**Figure 2.** Milk composition.

In terms of physical composition, milk is a complex polydisperse system containing many interconnected structural formations.

These structures include an emulsion dispersed system of fat globules, the structural system is colloidal, it consists of protein particles 0.2–1 microns in size. The composition of milk also includes a fractional system-true solutions of scattered molecules and atoms.

In milk quality control, samples are checked for acidity, antibiotic content, added water, fat, and protein. These analytical tests and methods are determined by international standards.
