Nowadays, the regulatory requirements for raw milk are described in the EU Food Code and the regulations of the European Parliament, which provide a detailed explanation of the traceability of raw milk. Regulation (EU) No. 178/2002 of the European Parliament and of the Council of 28 January 2002 describes the general principles and requirements of food law concerning food safety, as well as a package of so-called "hygiene regulations" governing the requirements for milk producers. raw materials, food producers, entities. It should be noted that according to the data, the protein content in milk harvested by processing enterprises is below 3.0% not only from March to May but even in the summer months. The requirements for the control of the qualitative and quantitative composition of the microflora contained in milk are becoming very important. Milk is a good nutrient medium for the development of most microorganisms (Vlasenko, et al., 2020). Specialists divide all microorganisms found in milk into three groups: technically important, pathogenic, and sanitary-indicative microorganisms. Sanitary-indicative microorganisms indicate the degree of contamination of milk and non-compliance with sanitary and hygienic production regimes. Thus, the quality of raw milk supplied to enterprises is one of the main problems that need to be addressed to improve quality and safety, increase yield and reduce the cost of finished products (Semko, Kolianovska, and Ivanishcheva, 2018).

The concept of functional foods as a source of protein, carbohydrates, and microelements consists of consuming products that offer various benefits that go beyond basic nutritional needs (Martirosyan, Singh, 2015).

Functional foods are designed to improve metabolic functions and biochemical parameters of the human body and help prevent non-communicable diseases such as cardiovascular disease (CVD), cancer, type 2 diabetes mellitus, and osteoporosis. Functional dairy products are the main suppliers of probiotic microorganisms, help to restore the gastrointestinal microflora. Strains of bifidobacteria and some lactobacillus species, such as Lactobacillus acidophilus, Lactobacillus casei subsp. casei, Bifidobacterium SPP. (B. adolescentis, B. animalis, B. bifidum, B. longum, B. breve), belong to probiotic cultures. They exert a positive effect on the human body and normalize the composition and functions of the bacterial flora in the gastrointestinal tract. (Breus et al., 2019).

The world's leading manufacturers and researchers of functional foods are France, Japan, Mexico, while the United Kingdom, the Netherlands, Germany, and Spain are among the European leaders. (Vicentini, Liberatore and Mastrocola, 2016). About 50% of healthy functional products are dairy products and about 30% are cereals.

Tackling the healthy nutrition issue is the most challenging and urgent task for the society and contemporary public health system. In the XXI century, a strategic line of the food industry consists in the attribution of special-purpose foods to the "healthy" diet.

One of the important components of any fermented milk drink is spirulina, which is widely used to improve the taste and protein content. A new technique for the manufacture of products using spirulina extract will become a new trend in the enrichment of traditional fermented milk drinks that heralds the innovative development of the dairy industry aimed at expanding the range of functional products.

In recent years, Ukrainian scientists have developed several products containing spirulina, although the assortment is still limited and does not meet the demand for such products. Raising consumer awareness of nutrient health benefits and nutritional value of components for potential disease prevention and health improvement will play the most significant role in the global food and nutraceutical market.

Functional products are considered medicinal products that are not only a source of energy and important nutrients but also good for health. Many studies, including some funded by the European Commission (EC), have led to an understanding of the potential mechanisms of biologically active food ingredients able to improve health and possibly reduce the risk of disease while improving overall wellbeing. Functional foods and nutraceuticals help improve health, reduce healthcare costs and promote economic development in rural areas. The demand for functional foods, especially in developed economies, is soaring now due to better awareness of the health benefits of functional foods and the growing gross income of households. The United States is the world's largest market for functional foods expecting to grow. This growth is mainly driven by the ever-increasing demand for energy drinks and enriched dairy products. Meanwhile, national rules and justifications for claims of no harm to health are among the most challenging problems that the functional foods and nutraceuticals market continues to face (Daliri and Lee, 2015).

Probiotics are considered single or mixed cultures of living microorganisms, which can change the intestinal microbiota and benefit the health of a host once ingested in sufficient quantities (Tiihonen, Ouwehand and Rautonen, 2010). Probiotic products contain live microorganisms over a dose recommended as good for health (5 × 109 CFU/day for 5 days) (Gupta and Garg, R., 2009).

Prebiotics are considered food components intended to selectively stimulate the growth and/or activity of intestinal bacterial strains capable of fermenting, for example, undigested starch, oligosaccharides, and nonstarch polysaccharides (Upadhyay and Moudgal, 2012). Synbiotics contain both probiotics and prebiotics and exert beneficial health activity as a result of the synergistic action of the two components (Scholz-Ahrens, et al., 2016).

Products that contain probiotics, including Lactobacillus strains and/or Bifidobacterium and less often Escherichia, Enterococcus, or Bacillus, include yogurt, kefir, buttermilk, acidophilus milk, sauerkraut, pickled cucumbers, tempeh, miso, and tea fungus (Zawistowska- Rojek, et al., 2016). Prebiotics are considered oligosaccharides such as fructooligosaccharides (inulin), galactooligosaccharides, xylooligosaccharides, cyclodextrins, and lactulose. Significant sources of oligosaccharides are chicory root, topinambur, raw garlic, onions, and whole grains (Al-Sherajiae et al., 2013).

The use of probiotics has been associated with improving immune function. Probiotics have been used for the treatment of gastrointestinal disorders such as constipation, diarrhea, Crohn's disease, irritable bowel syndrome (IBS), and diverticular disease. The health benefits of probiotics are closely associated with a proper balance of microflora in the digestive system (Clements and Carding, 2018).

Probiotics are considered useful once supported by prebiotics in a diet since they can stimulate the growth of bifidobacteria, which numbers are significantly reduced in humans within 55 to 60 years of age (Stavropoulou, and Bezirtzoglou, 2019). The health benefits of prebiotics consist in their ability to stimulate useful digestive activity, including bifidobacterial growth. Some prebiotics, not hydrolyzing in the human gastrointestinal tract, yet having other beneficial properties, such as inulin, which replace fat. Other prebiotics, such as fructans, contribute to the absorption of calcium, magnesium, iron, zinc, copper, and phosphorus. The dosage of fructans that exert the prebiotic effect ranges from 4 to 8 g per day (Gibson, et al., 2010).

The combination of pro- and prebiotics in the diet of elderly people is considered advantageous in terms of the ability to intensify the intestinal growth of bifidobacteria. The increased number of bifidobacteria contributes to the higher concentration of bacterial folic acid, vitamins B 1, B 2, B 6, and nicotinic acid. Therefore, bifidobacteria can be a source of essential nutrients and support the preventive measures and management of gastrointestinal diseases (Shoaib et al., 2016).

The most important group of products containing probiotics are fermented milk products (yogurt, kefir, buttermilk, etc.), cheeses, and tea fungus. Probiotic bacteria are present in some other foods, such as icecream, frozen desserts, fermented fruits, vegetable juices, and fermented meat (Zaręba and Ziarno, 2011). Probiotic bacteria are added to sweets, such as jelly candies, in combination with yogurt or chocolate, as well as to chocolate products in combination with lyophilized microorganisms, to grain juices, frozen yogurt, chocolate bars, cookies, and cereals (Semko, Vlasenko and Palamarchuk, 2020). Some probiotics are sold in the form of tablets or capsules. The new products are beverages containing probiotic bacteria in bottle caps, which run in the bottle contents once the bottle is opened (Kregiel, 2015). Traditional unrefined sources of prebiotics in the diet are soybeans, shelled wheat and barley, and raw oats. The food market also offers a variety of products with the addition of prebiotics and synbiotics, such as fermented dairy drinks, yogurts, fruit drinks, fatty spreads, meat products, mayonnaise, margarine, and pasta (Liutkevičius et al., 2016).

The use of probiotics and their positive effect on the digestive system have been substantiated by scientific data and approved by EU health regulators (Van Loveren, Sanz, and Salminen, 2012).

The purpose of the work is the development of a new functional fermented milk drink based on buttermilk using a complex of biologically valuable natural pro- and prebiotics originating from Spirulina platensis.

The authors developed a functional sour milk drink (Bultosa, 2016). The expediency and relevance of the use of secondary raw materials for the production of oil using specialized strains of the microorganism in the production of food products with a functional focus are described. (Bal’-Prilipko et al., 2016).

We present the development (Guneser, Hosoglu, Guneser and Yuceer, 2020) of a new functional sour milk drink from buttermilk with the use of natural pro- and prebiotics - with a biologically valuable complex Spirulina platensis (Kavimandan, 2015). The chemical composition of sour milk drink enriched with pro- and prebiotic cultures was studied (Fakhry et al., 2021). The main most common pro- and prebiotics, including strains, are specified Lactobacillus acidophilus, Lactobacillus casei subsp. casei, bifidobacterium SPP. (В. Adolescentis, В. animalis, B. bifidum, B. longum, B. breve) bacteria of starting cultures (Katla, et al., 2001). Lactobacilli are used from several different sources (Klein et al., 2000) have broad antimicrobial activity. Lactobacilli were used as probiotics in experiments to make the drink. Experiments on the development of fermented milk product according to the approved quality management system ISO 9001 and the developed procedure for tasting the drink contain organoleptic characteristics and a score (from 1 to 10) (Dal Bello, et al., 2017). To assess the basic chemical composition in the literature, different types of products were analyzed (Hayaloglu et al., 2008). Our studies have shown that with increasing administration of spirulina, the acidity of the drink increases disproportionately. With a spirulina content of 10 to 20%, the acidity of the finished product is acceptable. At introduction - 25% acidity for 5 hours makes 87 – 90 °T that testifies to the overestimated acidity of a product. Using the MIR technique, the average fat content of the beverage, which is 0.4%, the content of dry nonfat milk residue - 8.0, the acidity of the beverage 75 – 87 ˚T (Manuelian et al., 2017). Comparisons of proteolysis products obtained with different proteolytic drugs were studied (Yukalo, Datsyshyn and Storozh, 2019). The results of the studies corresponded to the chemical parameters for determining the degree of syneresis (C, cm³/100 g); product acidity (degrees T) and organoleptic parameters (OP, points) (Madalozzo, Sauer and Nagata, 2015). Samples No. 1, 2 and 3 in the work (Breus et al., 2019) similar in characteristics and meet the requirements for fermented milk drinks. The composition of buttermilk shows that its use for the production of fermented milk drinks is relevant. In this context, the problem of full and rational use of buttermilk is considered relevant (Manuelian et al., 2017). For the manufacture of sour milk drink (Polischuk et al., 2020) the degree of syneresis (serum isolation from the beverage clot) was investigated by centrifugation using a laboratory centrifuge Orbita (Ukraine). Rotation speed 1000 rpm, centrifuge tubes with a volume of 25 cm³ for 5 – 25 min and in terms of serum volume in cm³ per 100 g of product (Lange et al., 2020).

The synergistic properties of beverage clots were evaluated by the amount of whey released during protein coagulation (Atallaha, Morsyb and Gemiela, 2020). The dependence of the syneretic properties of buttermilk on the density of the clot and the duration of centrifugation of sour milk drink was determined. Analyzing the obtained data, it should be noted that the glossy clot with spirulina impairs the syneretic properties of the clot. After centrifugation for 5 – 25 min rennet clots obtained from buttermilk, which underwent two-stage pasteurization at different doses of spirulina, the amount of serum for centrifugation was: variant 1 sample - 77%, 2 samples - 74%, 3 samples - 71%, 4- sample - 68%. The lowest amount of serum was obtained in the sample with the highest dose of spirulina-25 (Patel et al., 2019). In the fourth sample, it was noted that the appearance and consistency have a heterogeneous structure, a clot with the release of serum drops, the taste and smell of grassy, greenish-gray color with spirulina. The overall score of the fourth sample is overestimated. Due to the deterioration of organoleptic parameters, the study of sample №4 was stopped.

Food manufacturers around the world are tasked with improving the quality, biological value, safety, taste, and range of certain foods, including functional foods (Türkmen, Akal and Ozer, 2019). Therefore, the development of the latest technologies for the production of fermented milk drinks based on buttermilk, suitable for all functional groups using the natural prebiotic spirulina, is considered a very promising task (Bultosa, 2016). In particular, on the basis of dairy products you can produce a wide range of health, medical and dietary products.

Therefore, research related to the processing of buttermilk and the search for alternative ways to use it as a raw material for the production of fermented milk drinks, supplemented with prebiotics, deserves to be introduced into production.

In our work, we present a recipe for a sour milk drink based on buttermilk and spirulina (Atallaha, Morsyb and Gemiela, 2020). We have developed a recipe for a functional milk drink based on buttermilk enriched with prebiotic spirulina (Leiss et al., 2008), can be used by dairy companies (Guneser et al., 2001).

Table 6 contains the chemical composition of the fermented milk drink enriched with pro- and prebiotic cultures.

Table 7 contains microbiological properties of fermented milk drink enriched with pro- and prebiotic cultures.

The degree of syneresis (serum isolation from the beverage clot) was studied by centrifugation using a laboratory centrifuge Orbita (Ukraine). Rotation speed 1000 rpm, centrifuge tubes with a volume of 25 cm³ for 5 – 25 min and in terms of serum volume in cm³ per 100 g of product.

The synergistic properties of the beverage clots were evaluated by the amount of serum released during protein coagulation. The dependence of the syneretic properties of the fermented milk clot on the density of the clot and the duration of centrifugation of the fermented milk drink is shown in Figure 6. Analyzing the data obtained, it should be noted that a loose clot with spirulina impairs the syneretic properties of the clot. After centrifugation for 5- 25 min rennet clots obtained from buttermilk, which underwent 2-stage pasteurization at different doses of spirulina, the amount of centrifugation serum was: option 1 sample - 77%, 2 sample - 74%, 3 sample - 71%, 4- sample-68%. The lowest amount of serum was obtained in the sample with the highest dose of spirulina-25.

Studies show that with the increasing introduction of spirulina, the acidity of the drink increases disproportionately (Figure 7). When the content of spirulina is from 10 to 20%, the acidity of the finished product is acceptable. At introduction - 25% acidity in 5 hours makes 87-90 °T that indicates the overestimated acidity of a product.

According to the approved quality management system ISO 9001, we created a tasting commission, which conducted a point evaluation (from 1 to 10) of the developed sour milk drink (Fig. 8). Samples No. 1, 2 and 3 are similar in characteristics and meet the requirements for fermented milk drinks. In the fourth sample it was noted that the appearance and consistency have a heterogeneous structure, a clot with the release of serum drops, the taste and smell are herbaceous, greenish-gray color with spirulina. The overall score of the fourth sample is inflated. Due to the deterioration of organoleptic parameters, the study of sample №4 was suspended.

Food producers around the world are challenged with the task of improving the quality, biological value, safety, taste, and the assortment of certain types of food, including functional products.

Analysis of buttermilk processing technologies shows that its use for the production of sour milk drinks is relevant. In this context, the problem of full and rational use of buttermilk is considered topical. Therefore, the development of the latest techniques for the manufacture of fermented milk drinks based on buttermilk suitable for all functional population groups using natural prebiotic spirulina is considered quite a promising task. In particular, it is possible to produce a wide range of health, medical and dietary products based on dairy products.

Having analyzed buttermilk processing techniques, we concluded that the issue of full and rational use of the material is still actual. Therefore, the study related to the processing of buttermilk and the search for alternative ways of using it as a raw material for the manufacture of fermented milk drinks supplemented with prebiotics is worth the whistle.

The recipe of fermented milk drink developed by us based on buttermilk enriched with prebiotic spirulina can be used by dairy establishments.

Table 10 contains the recipe of the fermented milk drink based on buttermilk.

The research results have shown that the subject drink is characterized by improved nutritional value and fit for human consumption.

Functional dairy products are the main suppliers of probiotic microorganisms, help to restore the microflora of the human gastrointestinal tract. Strains of bifidobacteria and certain species of lactobacilli, such as Lactobacillus acidophilus, Lactobacillus casei subsp. casei, Bifidobacterium spp. (B. adolescentis, B. animalis, B. bifidum, B. longum, B. breve), belong to probiotic cultures. The peculiarity of our proposed application of bacterial leavens is that after high-temperature treatment of buttermilk in the mode (100 ±5 °C) with a holding time of 25 s was cooled to 30 ±2 °C.

One of the important components of our sour milk drink is spirulina, which is widely used to improve the taste and enrich it with protein. We have developed an innovative technology for combining the unique food green algae Spirulina platensis with secondary raw materials fermented by selected strains of probiotic crops. Experimental studies have shown that a loose clot with spirulina impairs the syneretic properties of the clot, as evidenced by centrifugation for 5 – 25 min clots obtained from buttermilk, which has undergone 2-stage pasteurization. The lowest amount of whey was obtained in the sample with the highest dose of spirulina – 25. The optimal ratios of components (buttermilk, sourdough, sugar and spirulina) for the preparation of the food composition were determined. The parameters of the technological process of product preparation are established (fermentation in tanks t = 30 ±2℃, τ = 6 – 8 h before clot formation).

The resulting fermented milk drink is a polydisperse colloidal system in which the buttermilk is a dispersion medium, and the proteins of buttermilk and spirulina are the dispersed phase. The results showed that under the same conditions of the coagulation process with increasing amount of spirulina added from 10 to 25% changes the acidity of the finished product. According to research, in our opinion, the most rational is the content of spirulina 10% for all defined indicators.

In the innovative development of the dairy industry, the technology of products using the plant extract of spirulina will be a new direction of enrichment of traditional fermented milk drinks to expand the range of functional products. The developed product can take the place of a functional sour milk drink in the system of healthy nutrition of the population.

The proposed technology for the production of sour milk drink from buttermilk and spirulina content allows to obtain a drink with improved technological properties and increased biological value.