The composition and properties of cream with fat levels from 30% to 70% were investigated. It has been established that the decrease of fat level and, accordingly, the increase of plasma level in the cream leads to significant changes in the physicochemical parameters of the fat emulsion. Accordingly, the production of lowfat dairy products requires adjustment of the cream properties. It has been shown that using different doses of structure stabilizers: QNA colloid as a consistency stabilizer in the amount of from 1 to 2% and the Dimodan emulsifier U/G – from 0 to 1 % (Danisco, Denmark) changes the physicochemical properties (effective viscosity, sedimentation stability) and organoleptic properties (consistency, taste) of cream with fat level 40%. It has been conducted mathematical modeling, aimed to calculate dosing for improving the properties of milkfat emulsions, structure formation and further ensuring of the necessary consistency of cream pastes. Optimal doses of colloid QNA as a consistency stabilizer and a U/G Dimodan emulsifier have been determined. It has been established that their content should be 1,0% and 0,5%, relatively, for pastes with a fat level of 40%. The effectiveness of the joint action of consistency stabilizers and emulsifiers in obtaining milkfat emulsions were defined by the level of effective viscosity. Moreover, the use of the emulsifier had less effect on the effective viscosity of the milkfat emulsions. It has been found that using the structure stabilizers could improve the formation of lowfat products and the formation of the desired pastelike consistency of highfat cream with a fat level of 70%. Thus, it is possible to adjust the composition and properties of raw material as a basis for milkfat emulsions by optimizing the ratio of structure stabilizers. Comparative evaluation of the physicochemical properties of milkfat emulsions and highfat cream makes it possible to predict their potential for conversion into a creamy paste with a given consistency.
In the current conditions of the current shortage of milk raw materials and the full utilization of the secondary raw material potential of the dairy industry and dairy enterprises of Ukraine today are focusing on the creation of a new group of dairy products. This group is based on the low content of milk fat, the effectiveness of various conditions of thermomechanical treatment for the conversion of milk fat emulsions into a quality product.
In particular, oil and cream pastes are promising for improving the efficiency of the dairy industry and for providing various consumer needs. According to world standards (
The development of lowfat dairy products with a fat content of 3040% is complicated by the deterioration of the thermomechanical treatment of lowfat milkfat emulsions. The complication is caused by a change in their physical and chemical properties (
Therefore, the manufacture of a highquality emulsion product with a high content of milk plasma, first of all, involves the choice and the right combination of stabilization systems: consistency stabilizers and emulsifiers. The action of emulsifiers is due to their ability to accumulate at the boundary of two liquid phases, reducing interfacial tension and creating a protective layer around the droplets that prevents coagulation and coalescence. We agree with the authors (
Typically, to stabilize lowfat emulsions, it is necessary to use mixedtype emulsifiers that combine hydrophilic and hydrophobic compositions. They have maximum functionality and allow them to create a wide range of emulsion products with specified properties. The most common emulsifiers include mono and diglycerides of dietary fatty acids, lecithin and phospholipids, emulsifiers based on polyglycerol, and others. In the writings of the authors (
Also, they must meet certain requirements: be physiologically safe, promote the retention of moisture in the product during machining in the production process, stabilize high and lowdispersion emulsions, increase their stability, and ensure the stability of the product during storage. When choosing an emulsifier take into account the melting point, iodine number, characterizing the degree of saturation. For example, in studies (
The authors (
Several authors (
Ensure the stability of the direct type emulsion needs to use surfactants, in which there is a dispersion of the fat phase, increase of the organoleptic and physicochemical characteristics of the finished product.
The process of forming the properties of milkfat emulsions with the phase structure of "fat in the water" under the influence of structure stabilizers for cream pastes is aimed at the creation of the new technologies of lowfat buttermaking products. Direct control of the composition and properties of the raw material – cream with a fat content of 40%, depending on the dose of the structure stabilizers could ensure a stable structure.
It has been determined physical and chemical properties of milkfat emulsions as a basis for the production of cream pastes for the realization of this hypothesis and achievement of this goal.
The objects of this study were milk fat emulsions with a fat level of 30% with adding of the structure stabilizers and cream with fat level from 30% to 70% and, accordingly, a solids level from 2.5% to 9.3%. Highfat cream was obtained by the method of double separation.
The physicochemical properties of cream were determined according to the recommendations of the author (
The physicochemical properties of cream and cream with added structure stabilizers were investigated by the sedimentation resistance of the emulsions to delamination, according to the method (
The effective viscosity of cream and cream with added structure stabilizers was determined by the rotary viscometer “Rheotest II” with a cylinder/cylinder measuring system (S/S1, S/S2, S/S3) for different viscosities according to the instructions. In the gap between the cylinders made cream, in which under the influence of the rotation force of the rotor was shifting one layer of the bunch relative to another. The rheological characteristics of the product were determined by the speed of rotation of the rotor and the force of resistance of its rotation. The measurements were performed at a strain rate of 48.6 s^{1}. The parameters of the instrument were translated into the shear stress (PA) at a given strain rate by the formula:
where:
τ – shear stress, Pa;
α – indicators of the device;
Z – cylinder constant, Pa / unit. scale instrument.
The effective viscosity of the test samples was determined by the formula:
Where:
η _{eff}  effective viscosity, Pa
Dr – shear stress, Pa^{2}/sec. Dr=constfor each mode of clot destruction.
Milkfat emulsions were prepared based on skim milk and highfat cream with a fat content of 70% by weight. For this purpose, the stabilizer was separately dissolved in skim milk, heated at (45 ±5 ºС), and the emulsifier in high fat cream at temperature. The components in the quantities determined in the experimental conditions were combined to obtain normalized cream with a mass fraction of fat, respectively, 30% and 40%. The resulting mixture was heated to (80 ±1°C) with continuous stirring, followed by cooling to (15 ±1°C). Component ratios were varied to normalize cream 30% and 40%.
A software package STATISTICA^{©} v 5 for Windows (StatSoft Inc., USA) was used to processing of the obtained experimental data according to the recommendations of the author (
The results of the studies were evaluated according to the significance level of
Graphic processing of the results is done using the software Microsoft Excel 2010. Іnc, Mathsoft Mathcard Enterprise Edition ON V11. A.
Also, a multivariate regression analysis of the experimental data was performed to evaluate the effect on the studied performance of each of the factors introduced into the model at a fixed position at the average of the other factors. An important condition is the lack of a functional link between the factors. For this purpose, a mathematical model was constructed in the form of an analytical expression that best reflected the relationship of factor traits with the resultant one. To obtain stable milkfat emulsions, mathematical modeling was performed using a twofactor linear regression model, which in general looks like:
Where:
To obtain stable milkfat emulsions:
Y_{1} – effective viscosity; Y_{2} – taste, and smell; Y_{3} – consistency; Y_{4} – sedimentation stability;
In the study, the mathematical expectation of random deviation ε_{i} is 0 for all observations (M (ε_{i}) = 0).
To evaluate unknown parameters
The modeling and processing of the experimental data were performed using a mathematical package MathCad. For emulsions with a mass fraction of fat 40% the equations of mathematical models have the form:
1) The equation that describes quantitatively effective viscosity:
2) An equation that quantitatively describes taste and smell:
3) The equation that describes quantitatively consistency:
4) Equation quantitatively describing sedimentation stability:
The adequacy of the models was verified by the coefficients of determination R^{2}_{Y1}=96 %, R^{2}_{Y2}=98 %, R^{2}_{Y3}=91 %, R^{2}_{Y4}=92 %, which testify to the highquality character of the correlation of the system coefficients, as well as the Ftest (Fisher's Ftest) and the Student's tdistribution to evaluate the reliability of the correlation coefficients.
For a comprehensive analysis of the change in the properties of cream with a fat content of 40%, depending on the dose of the stabilizers of the structure and to determine the rational ranges of the stabilizers, a multidimensional regression analysis of the experimental data was performed.
Based on the results of the experimental studies, a twodimensional approximation of the mathematical dependence was performed f = φ(x,y) – a mathematical model that reproduces with sufficient accuracy the studied regularity y = f(x,y) – experimental data.
Functional dependencies in the form of twodimensional seconddegree polynomials are described, which describe the technological process fairly accurately. The simulation results are presented in Figure
Graphic 3D models (a, b, c, d – 1) and rational ranges (a, b, c, d – 2) of the influence of independent factors x and y on the basic physicalstructural and organoleptic parameters of milkfat emulsions with a fat content by weight of 40%.
Analysis of the studies showed that the optimal indicators for Y_{1}are 50.36 Pa∙s; for Y_{2}is 4,7 points; for Y_{3}is 5.0 points and Y_{4}is 82.2 % by making 1.0 % of stabilizer and 0.5 % of emulsifier.
Equations that adequately describe the result of the experiment for a 40% mass fraction of fat have the following form:
The results of the researches made it possible to determine the influence of all independent factors on the formation of physicalstructural and organoleptic parameters.
The decrease in the fat level in the production of lowfat pastes (30 – 40% of fat) causes a decrease in their viscosity, the stability of structuring, regardless of the hardware design process. Several researchers (
Physicochemical indicators of cream of different fat content as raw material for paste production.
Mass fraction of fat cream, %  The ratio of mass fraction of fat / MSNF  Precipitate of fat, %  Effective viscosity, Pa·s 



70  27.91  96.0 ±1.0  13.789 ±0.50 
50  11.96  85.9 ±0.8  0.818 ±0.009 
40  7.97  85.1 ±1.0  0.072 ±0.008 
35  4.99  74.5 ±1.0  0.054 ±0.006 
30  3.22  64.0 ±0.9  0.036 ±0.006 
In particular, a decrease in the fat mass from 70 to 30% in the cream resulted in a decrease in their viscosity from 13.789 to 0.036 Pa·s. Cream with a mass fraction of fat 30 40% by this indicator approached each other and was in the range of 0.0360.072 Pa·s. The stability of fat emulsions is the inverse of the amount of fat and directly proportional to the ratio in them Fat/ DSMR. Sedimentation resistance with mass fraction of fat 50%, 40%, 35% and 30% was lower respectively on 10.5%, 11.4%, 22.4%, 33.3%, than in cream with a mass fraction of fat 70% (Table
The data obtained indicate that a decrease in the fat content of the cream and, consequently, an increase in the plasma, leads to significant changes in the indicators, which impair the ability of the cream to turn into oily products and stabilize their structure To improve the ability of the cream to machining and the formation of a homogeneous stable structure of the products of lowfat content requires changes in the properties of the original cream (Rybak, 1997;
Dependency of change in effective viscosity and sedimentation resistance to increasing the dose of stabilizers in milkfat emulsions.
In this regard, for direct control of the properties of milkfat emulsions (mass fraction of 40% fat as a basis for the production of pastes and optimization of doses of structure stabilizers relative to the mass fraction of fat, which would provide milkfat emulsions physical indicators close to the control cream (70% fat by weight)) were studied the effectiveness of the joint action of consistency stabilizers on the example of QNA colloidal in the amount of 1 to 2.0% and the emodulator of the dimodan U / G  from 0 to 1.0% and the dependences of changes in physicochemical and organoleptic properties were determined.
The results of the analysis of changes in the properties of cream with a fat content of 30 – 40% using a stabilizer and emulsifier are presented in Table
The change in the properties of cream with a mass fraction of fat 40% depending on the dose of the stabilizers of the structure.
Mass part of the stabilizer, %  Mass fraction of emulsifier, %  Effective viscosity, Pa·s  Taste and smell, points  Consistency, points  Sedimentation stability, % 

0.5  0  24.3 ±0.5  4.5  3.0  85.1 
0.5  0.5  32.3 ±0.9  4.5  3.7  86.0 
0.5  1  35.5 ±0.9  3.5  3.0  86.4 
1  0  48.6 ±0.8  5.0  4.5  83.2 
1  0.5  50.4 ±1.6  5.0  5.0  82.2 
1  1  56.1 ±1.6  4.0  2.5  88.8 
1.5  0  52.4 ±1.6  4.5  4.2  82.7 
1.5  0.5  56.1 ±1.6  4.5  4.0  82.3 
1.5  1  68.9 ±1.6  3.0  3.0  80.6 
It has been found that with increasing doses of structure stabilizers, effective viscosity increases in milkfat emulsions. And sharing emulsifier and consistency stabilizer is more effective. It should also be noted that adding 40% fat to the emulsifier had less effect on the effective viscosity of the milkfat emulsions. Significant changes in this indicator occurred due to the introduction of the stabilizer cream.
Obtaining stable milkfat emulsions with corresponding structural and mechanical properties has a narrow range of a mass fractionі of the stabilizer of consistency (
The viscosity of cream with a fat level of 40%, even with 0,5% of the stabilizer addition was in 1.7 times higher than the viscosity of the control cream with a fat level of 70% and values 13.789 Pa·s (tab. 2). Instead, the addition of 1 and 2% of stabilizer resulted in a 3.5, and 3.8 times increase in the viscosity of the cream. Accordingly, compared to the control cream results were in diapason ranged within 48.652.4 Pa·s.
There was no clear trend in the adding of structure stabilizers in cream with 40% fat content. In particular, some samples showed an increase in sedimentation resistance of up to 4.4%, while in others a decrease in sedimentation resistance was observed.
A certain pattern in the study of the sedimentation stability of cream, depending on the doses of stabilizers and emulsifiers was not found by another researcher (
Taste and odor, as well as the consistency of the samples of milk and fat emulsions, were determined on a specially designed 5point scale (Table
Scale of organoleptic evaluation of milkfat emulsions to obtain cream pastes.
No.  Characteristic  Points  



1  Pure, creamy, without the foreign flavors and odors of structure stabilizers  5.0  
2  The creamy taste and smell are not pronounced enough  4.0  
3  Not expressed creamy, slightly foreign  3.0  
4  Slightly unclean, with a foreign taste and the smell of consistency stabilizers and emulsifiers  2.0  
5  Strange flavors and smells of stabilizers and emulsifiers of structure are pronounced, bitterness is felt  1.0  
1  Dense, plastic, homogeneous  5.0  
2  Too tight, homogeneous, slightly powdery  4.0  
3  Pasty, not dense, creamy, homogeneous, low fatness  3.0  
4  Pasty, heterogeneous, sticky, refractory or sour cream, very viscous, sandy  2.0  
5  Liquid, unstable  1.0 
Dependence of organoleptic parameters of milkfat emulsions on mass particles of stabilizer and emulsifier: taste and smell, consistence.
In all investigated variants of milkfat emulsions using structure stabilizers, there was a tendency to improve the consistency due to the increase of their plasticity. The highest consistency was milkfat emulsions with a fat content by weight of 40%, obtained with the use of stabilizer and emulsifier in quantities of 1.0% and 0.5%, respectively. Milkfat emulsions with the only stabilizer in quantity were also highly rated 1.0 %. Milk and fat emulsions using stabilizer up to 1.0 – 1.5% and emulsifier 0.5% by taste were acceptable. Increasing the emulsifier to 1.0% worsened the taste of the emulsion due to the foreign taste of bitterness.
Thus, the results of studies on the effect of stabilizers and emulsifiers on the viscosity of milkfat emulsions with a fat content of 40% suggest that adding stabilizers of the structure makes it possible to approximate the structural and mechanical properties of the cream 70% fat.
Thus, the data obtained by us indicate that lowfat cream with a high plasma content is significantly different in physicochemical properties from highfat cream, which are a key factor in the formation of plastic fat bases (Viriato, et. al., 2016, Ribeiro, et. al., 2015). Our findings are consistent with the results of the authors' research (
It has been established the dependence of changes in the physicochemical properties of cream with fat level of 40% by the dose of the stabilizers of the structure. In particular, with increasing doses of stabilizers of the structure and mass fraction of fat in milkfat emulsions, the effective viscosity is increased and the consistency score is increased by increasing their plasticity. It should be noted that common use of emulsifiers and consistency stabilizers are more effective. According to the research results, it has been established that the selected parameters affect on the efficiency of the milkfat emulsion. However, the formation of the structure is more influenced by consistency stabilizers than emulsifiers.
Thus, optimized doses of structure stabilizers will provide physicochemical and organoleptic indicators close to the control cream in the original lowfat cream. In particular, for milkfat emulsions with a fat level of 40%, the QNA colloid stabilizer and the dimodan U/G emulsifier are respectively in the amounts of 1.0% and 0.5%.
