3 experimental part

Key raw milk indicators by season of the year

As the quantity and quality of raw milk depend on the season of the year and the diet of the animals, further studies examined the change in fat, protein and density content of raw milk in different seasons of the year [35,36]. The indicators were investigated in the spring, summer and autumn and winter periods of 2015-2016. The results of the experimental studies are presented in the table 12.
Table12 - Raw milk indicators by season of the year

Milk	Autumn	Winter	Spring	Summer		Average value
	Mass fraction of protein, %
Cow	3,15±0,09	3,11±0,06	3,09±0,05	3,06±0,03		3,1±0,09
Goat	3,13±0,06	3,24±0,03	3,15±0,07	3,03±0,05		3,14±0,06
	Mass fraction of fat, %
Cow	3,35±0,08	3,46±0,07	3,38±0,08	3,29±0,06		3,37±0,05
Goat	3,27±0,06	3,7±0,07	3,43±0,05	3,0±0,05		3,35±0,02
	Density, kg/m^3
Cow	1028,7±0,19	1028,88±0,20	1028,7±0,14	1028,55±0,15		1028,71±0,12
Goat	1027,43±0,15	1028,13±0,13	1027,4±0,12	1027,43±0,13		1027,6±0,16

Fluctuations in the main indicators of raw milk are due to many factors. The fat M.D. of both cow's and goat's milk is slightly higher in winter than in summer.

The analysis of the data obtained from the studies leads to the conclusion that, in terms of its properties, milk can be used as a raw material for the production of soft cheeses without ripening.

3. Indicators of mixed raw milk compositions

Milk (cow/goat)	Indicators
	Mass fraction protein, %	Mass fraction fat, %	Density, kg/m^3	Acidity, T
100/0 (cow)	3,11±0,06	3,32±0,08	1028,87±0,17	17±1
75/25	3,03±0,08	4,03±0,07	1027,8±0,21	17±1
50/50	3,06±0,07	3,76±0,06	1028,13±0,19	17±1
25/75	3,04±0,06	4,04±0,08	1027,81±0,13	17±1
0/100 (goat)	3,02±0,07	4,29±0,08	1027,56±0,18	16±1

One of the objectives of the work was to formulate mixed compositions of dairy raw materials to produce a high quality product. In connection with this task, various cow's and goat's milk mixture compositions were made and the physical and chemical composition of goat's and cow's milk as well as their various compositions on the basis of milk obtained in the conditions of ZAO Prinevskoye farm were studied. The results are given13 in the table below. Table 13- Composition of raw milk compositions

According to the results of studies on the composition of raw milk compositions, it can be observed that with the increase of goat milk added to the mixture, the protein mass fraction content increases, as well as the dry matter content in the mixture, which must be taken into account when normalising the dairy raw materials.

4. Determining the cheesiness of raw milk

Cheesiness is a set of indicators of chemical composition, physical and chemical, technological and hygienic properties [9].
Cheese suitability is determined by a rennet curdling time test using the VNIIMS instrument, as well as by additional tests such as the rennet test, which characterises the curdling ability of milk, and the reductase test, which is used to determine the total number of micro-organisms [62].
The ability of milk to form a firm clot under the action of the rennet is of particular importance in the production of the product. In practice, this ability of milk is tested by means of a rennet sample. The method is based on the ability of heat-treated (pasteurised) milk to curdle under the action of rennet. The quality of the raw milk is assessed for its suitability for cheese production by the nature of the clot formed.
The samples of cow's and goat's milk, as well as their blended compositions, can be assessed as "Good" and classified as1
- The resulting clot had a smooth surface, was resilient to the touch and had no eyelets on the longitudinal section.
The raw milk was then tested using a reductase test. Goat milk, cow milk and their blended compositions can be classified as class 1 according to the bacterial contamination levels.
The dose of clotting agent as well as the clotting time depend on the acidity of the milk, the fractional composition of the proteins and other factors that determine the rate of clot formation. The duration of milk clotting and the strength of the clot depend on the amount of enzyme added. The duration of milk clotting was 30 min.
The results of studies to determine the amount of rennet used in the production of the product to coagulate milk in 30 minutes are shown in the table 14.
Table14 - Amount of rennet

Amount of preparation, g per kg100 milk	Milk (cow/goat)
	100/0 (cow)	75/25	50/50	25/75	0/100 (goat)
Rennet enzyme	1,1±0,10	1,1±0,15	1,25±0,10	1,35±0,15	1,5±0,20

From the experimental data presented, it can be seen that the amount of rennet introduced for goat milk curdling is greater than for

of clotting of cow's milk and 50/50 blended compositions (per min30), by 26% and 16% respectively.
One of the most important indicators determining the cheeselessness of milk is its protein content. The results of analysis of physical and chemical parameters indicate the high quality of cow and goat milk obtained in the conditions of ZAO Prinevskoye farm and the suitability of raw milk for further research on the development of recipes for soft cheeses without ripening.
Another important parameter determining the clotting ability of milk is its inhibitory substance content. Inhibitory substances were determined in the milk to be tested [38].
The test result showed that the contents of the test tubes were white, indicating the absence of inhibitory substances in the goat and cow milk raw materials tested (and in the control sample).
Based on the results of this research, it can be concluded that cow's and goat's milk as well as their blended compositions meet the cheese suitability requirements and can be used in further research into the development of soft cheese prototypes.

3.