Study of the nutritional value of fermented milk drinks from goat’s milk

The primary aim of this paper is to explore the nutritional value of fermented milk drinks from a goat. A vegetable component was used as fillers, including amaranth flour, flour from kumarshik, fruit and berry filler: irga, black chokeberry, and black currant. This study's specific objectives were to determine organoleptic and safety indicators and study the shelf life of finished fermented milk drinks from goat milk with various fillers. A detailed technological scheme for the production of fermented milk drinks was drawn up. In the study, the rational formulation of fermented milk drinks was determined using the "Search for solutions" program MS Excel.


Introduction
Recent trends in healthy food have led to a growing academic interest in the nutritional value of products. Nutritional value is a concept that reflects the full completeness of the useful properties of a food product, including the degree of meeting the physiological needs of a person in basic nutrients, energy, and organoleptic qualities. It is characterized by the chemical composition of the food product, taking into account its consumption in generally accepted quantities [1].
Calculation of nutritional value is carried out for 100 g of a fermented milk drink with a fruit and berry component, by calculation, depending on the raw materials.
The energy value is the amount of energy formed during the biological oxidation of fats, carbohydrates, and proteins in the product [1].
The energy value (EV) of a food product is calculated using the formula 1: where EC is the energy value of 100 g of food, kcal; Content in g / 100 g of product: P -proteins, F -fats, C -carbohydrates, OA -organic acids; The number of kcal formed during the combustion of food substances: P = 4.0 kcal; F = 9.0 kcal; C = 4.0 kcal; OA = 3.0 kcal.
The digestibility of nutrients depends on their ability to be absorbed from the gastrointestinal tract. The quantitative absorption capacity (digestibility coefficient) is expressed as a percentage of the total content of a given food substance in a product or diet. With a mixed (consisting of animal and plant products) diet, the coefficient of assimilation of proteins is on average 84.5%, fats -94%, carbohydrates (the sum of digestible and indigestible carbohydrates) -95.6% [1].
The energy value (EC) of a food product, taking into account the coefficients of assimilation of nutrients, is calculated according to formula 2: Energy values are calculated per 100 g of food and are expressed in kilocalories and kilojoules [1].

Materials and methods
Research objects: raw material -goat milk (Zaanen breed), vegetable fillers, finished products: fermented milk drinks from goat milk with fillers.
Technological process Reception and preparation of milk. Milk and raw materials used in producing a fermented milk drink are taken according to the quantity and quality established by the enterprise's laboratory. The milk is weighed, cleaned from mechanical impurities in separators -milk purifiers and a deaerator, to remove extraneous tastes and odors. It is recommended to warm milk up to 30 °С -40 °С before filtering (Kryuchkova, 2018) [4].
Normalization. Goat milk selected for quality is normalized in terms of fat content. Part of raw purified milk, preheated to a temperature of (42±3) °C, is sent to a cream separator. The cream obtained during milk separation is pasteurized at a temperature of (88±2) °С, cooled to a temperature of (4±2) °С and sent for storage, or immediately sent for processing at a temperature of (42.5±2.5) °C. The fat mass fraction and acidity are determined in the cream. Skimmed goat milk is pasteurized at a temperature of (76±2) °С with an exposure of (18±2) s, cooled to a temperature of (4±2) °С and sent to a transitional storage tank, or immediately sent for processing at a temperature of (42 ± 3) °C (Kryuchkova, 2018) [4].
The mixture is normalized by the mixing method. In this case, the mass of products for mixing is determined by the formulas of the material balance or by the recipe so that the mass fraction of fat and dry matter in the finished product is not less than the mass fraction of fat and dry weight stipulated by the technical specifications (Kryuchkova, 2018) [4].
The normalized mixture is first heated to a temperature of (60±5) °C. Then the mixture is subjected to pasteurization (in a pasteurization unit) at a temperature of (85±2) °C with a holding time of 8 to 10 minutes, or 90 °C with a holding time of 20 seconds. With the selected heat treatment mode, the best conditions are created for the destruction of unwanted microflora. The pasteurized normalized mixture is cooled to the fermentation temperature -from 40 °C to 42 °C (Kryuchkova, 2018) [4].
Further, the pasteurized normalized mixture is subjected to ozonation for 10 minutes at an ozone concentration of 80 mg/m 3 ; due to ozonation of goat milk, it turns out to increase the microbiological safety and taste characteristics of fermented milk drinks from goat milk.
The tank is filled with the mixer's mix to mix the mixture with the starter culture better. Stirring is finished 15 minutes after filling the reservoir. Then, herbal components are added to the prepared homogenized mixture: 1 -black currant, chokeberry, irga. The mix of fruit fillers is ozonized for 10 minutes before adding to the drink at an ozone concentration of 85 mg/m 3 (Shunekeeva and Alimardanova, 2020) [2].
2 -flour from kumarshik and amaranth. A mixture of kumarshik flour and amaranth was ozonized for 10 min before adding to the drink at an ozone concentration of 115 mg/m 3 (Shunekeeva and Alimardanova, 2020) [3].
They are added to a mixing vessel for even distribution. Stirring continues for 5 minutes to 7 minutes. Due to the use of ozonation of vegetable fillers, organoleptic characteristics are increased; the shelf life of drinks is extended to 14-15 days.
The mixture is fermented at a temperature from 40°C to 45°C until a tender, sufficiently dense curd is formed, without signs of separation of whey with an acidity of about 90 °T or pH from 4.4 to 4.2 units (acidity is slightly lower than in the finished product). The clot's ripening is carried out at a temperature of 12-14 °C and lasts from 6 to 8 hours (Kryuchkova, 2018) [4].
After fermentation, the product is pumped to a tubular cooler, where it is cooled to a temperature of 30 °C to 32 °C.
Next, bottles made of polymeric and combined materials of various capacities (from 200-500 ml) were packaged, the resulting fermented milk drinks were cooled to a temperature of (4±2) °C, where they are stored until sale in refrigerating chambers (Kryuchkova, 2018) [4].

Results and discussion
In terms of organoleptic characteristics, the product must meet the requirements specified in table 1. In terms of physical and chemical indicators, fermented milk drinks from goat milk with vegetable fillers must meet the requirements specified in Table 2. In terms of microbiological indicators, the product must comply with the requirements of the technical regulations of the Customs Union TRCU 021/2011 "On safety of food products" and the technical regulations of the Customs Union TR CU 033/2013 "On the safety of milk and dairy products," given in Table 3 (TR CU 021    The product contains all the macronutrients necessary for the human body. As can be from Tables 4 and 5, the product contains mostly carbohydrates.
The digestibility of carbohydrates is very high; therefore, these fermented milk drinks can be considered a useful energy source for its consumers.
By a similar method, the energy value for the national milk-cereal drink made from goat's milk was calculated; the results obtained are shown in Table 5. Milk proteins (caseins) are biologically complete, as they contain all the essential amino acids. Milk fats (lipids) are the most valuable energy sources for the body. The developed fermented milk drinks from goat milk have a high nutritional and energy value due to the introduction of fruit, berry, and cereal components into their composition.

Studying the storage capacity of fermented milk drinks from goat milk
To substantiate the shelf life, the influence of the presence of cereal and fruit and berry fillers on the organoleptic, physicochemical, and microbiological indicators of fermented milk drinks from goat milk during their storage was studied.
Storage tests were carried out for 15 days.
After the end of the fermentation process, the products were packed into plastic cups with a capacity of 400 ml and placed in a chamber with a temperature of (4±1) °С, where the storage process was carried out. The consistency, taste, and smell of fermented milk drinks with vegetable fillers remain at a high level for 15 days of storage and are 4.8±0.2 points. During storage, the titratable acidity of the produced fermented milk drinks was measured.
The research results are presented in Table 6. As a result of the study, it was found that the accumulation of lactic acid in drinks does not stop, and the titratable acidity reaches 118 ± 2 °T by the end of the shelf life. The addition of plant components contributes to a slight increase in the acidity of the product during storage.
Due to bifidobacteria's high activity, the total number of microorganisms changes insignificantly and throughout the entire storage period corresponds to the norm for fermented milk drinks: pathogenic microorganisms, incl. Salmonella, BGKP (coliforms), S. aureus are absent in ready-made drinks.

Calculation of the recipe for fermented milk drinks based on goat milk
The raw materials for producing fermented milk drinks are whole and skim goat milk, starter culture, and vegetable filler.
The amount of required raw materials and other materials is calculated based on the product calculation for a given product type.
Delivery costs of starter cultures -2% of the cost of raw materials and other materials. The calculation of the cost of raw materials and other materials is presented in Table 7.
With the given ingredients and restrictions, the recipe composition and the cost of the product were determined. Based on the information matrix of data, a system of linear balance equations for fat, protein, dry substances, water, and the mass of fermented milk drinks are formed (Table 8). The task is realized by solving a system of linear balance equations and constraints [5]. As a criterion for optimizing the recipe, the goal function was chosen -the minimum cost of the product, which will be written in the form: minF (x) = (350 • X1 + 160 X2 + 1200 • X3 + 541667 • X4) The solution of the system of linear balance equations is carried out in the MS Excel system using the add-in program "Solver" (Lisin, 2016) [5].
The calculation of the cost of raw materials and other materials is given in Table 9.

Conclusions
The findings reported here suggest that: 1. The nutritional and energy value for ready-made fermented milk drinks from goat milk with vegetable fillers has been determined.
2. An information matrix was compiled based on which systems of linear equations were obtained to optimize the formulation of fermented milk drinks from goat milk with vegetable fillers.