Production technology of soy protein additives for use in meat products

. Nowadays, the average person's diet does not contain enough foods that are high in readily absorbed proteins. Using cheaper and healthier vegetable proteins in favor of animal proteins is one option to address this issue. The only crop with high-quality protein is soy. With the exception of methionine and cysteine, soy protein has a good balance of all the necessary amino acids. 15–25% of proteins are found in meat products. There are no other vegetable legumes (beans, peas) with a protein content (44–45%) and oil (20–22%) as high as vegetable soybeans while they are in the green bean phase. This crop is particularly nutrient-dense, and adding vegetable soy to diet enables to add proteins and other essential elements to cuisine. As soy protein is more similar to proteins of animal origin in terms of protein complexity and the presence of key amino acids (lysine, tryptophan, etc.), both animal and human organisms require less energy to transform soy protein into body proteins. The use of soy protein additives in meat products leads to enrichment with proteins and a significant improvement in the functional and technological properties that determine the structural and mechanical characteristics of the combined meat products.


Introduction
Currently, there is a lack of food rich in easily digestible proteins in the diet of the population. One way to solve this problem is to replace animal proteins with vegetable proteins, which are both cheaper and healthier. Soy is the only crop that contains high quality protein [1]. Soy protein is well balanced in essential amino acids, except for methionine and cysteine. According to the protein complex and the content of essential amino acids (lysine, tryptophan, etc.), soy protein is closer to proteins of animal origin, so animal and human organisms spend minimal effort to convert soy protein into body proteins [2].
Meat products contain 15-20% protein. Among vegetable legumes (beans, peas) there are no equal vegetable soybeans in terms of protein content (44-45%) and oil (20-22%) in the green bean phase. This is a very highly nutritious crop, and the inclusion of vegetable soy in the diet allows to enrich food with proteins and other nutrients necessary for the body [3].
Numerous studies confirm that soybeans contain antioxidants. Its use in food helps to increase the body's immunity and reduce allergies [4][5][6]. Unlike meat, soy does not contain cholesterol and saturated fatty acids, which lead to heart disease, cancer, and osteoporosis. Soy has been shown to effectively reduce blood cholesterol levels, optimize blood glucose levels in diabetes, strengthen bones, prevent heart and blood vessel disease, and reduce the risk of kidney and liver stones. Soy contains a very rare fatty acid -omega-3, which is necessary for brain development in newborns, reducing the risk of heart disease and cancer. It contains many anti-carcinogenic substances that prevent and stop the development of cancerous tumors.
The use of soybeans is carried out in several directions, among which the following lines are distinguished [7].
Soy proteins are made from raw beans using multi-stage processing technology to remove indigestible components and concentrate the protein. The type of end product depends on the type of processing. The protein can take the form of a concentrate, isolate, or flour. In addition to protein, soy products contain no less valuable components -fiber, isoflavones, saponins.
The ideal raw material for the production of soy protein supplements is full fat extruded soy. The content of vitamins and essential amino acids in concentrates is much higher than in other types of proteins of animal and vegetable origin [8,9].
On the basis of protein, highly effective protein-vitamin and mineral complexes are obtained -soy protein concentrates, consisting of soy proteins, vitamins, minerals and enzymes [10,11].
The introduction of soy protein concentrates, consisting mainly of salt-soluble proteins, into meat systems ensures the formation of meat emulsions, stabilizes their properties, increases the level of fat absorption, water-binding capacity and minced meat stickiness. As a result, the yield of finished products increases, the probability of formation of bouillon-fat edema is excluded, solidity and juiciness of the product is formed.
In terms of their functional and technological properties, soy protein concentrate acts similarly to the structure-forming muscle proteins of lean meat. However, unlike multicomponent meat and milk proteins, soy protein concentrate is homogeneous and this makes it easy to predict and control the nature of technological changes in meat emulsions when working with it.

Materials and methods
The methodology of research works is based on the justification of the choice and application of a set of tools, methods and techniques in the conduct of experimental studies and the analytical evaluation of the results obtained.
Due to the stability of the composition and functional and technological properties, the soy protein supplement provides a significant improvement in the quality of meat emulsions prepared from low-grade raw materials with a wide range in the content of muscle, fat and connective tissue, as well as from frozen and thawed meat.
Soy protein supplement can be used both for the production of a wide range of traditional meat products, and for the production of new types of products. At the same time, the optimal level of its introduction into the formulations of various types of meat products is: for boiled sausages, sausages, sausages -2-4%, for products such as ham in the casing -2-4%, for salted pork products (when introduced as part of brines) -12%, for pâtés (shaped, in casing and canned) -3-6%, for chopped semi-finished products -up to 7%, for dry fermented sausages -2-3%.
Characterizing soy protein concentrates as functional ingredients, the following indicators were chosen as the main criteria for assessing their structural similarity with meat systems: solubility, water-holding capacity, critical gelation concentration, emulsion stability, and fat-retaining capacity of dry preparations.
Solubility is used as a primary indicator of the quality of a food protein. For example, an increase in the solubility of a protein contributes to an increase in the stability of emulsions stabilized by it. The most important functional families of a protein include the value of the critical concentration of its gelation, at which a spatial network is formed in the entire volume of the system.
The amino acid composition data indicate that all samples, regardless of the content of other modified proteins, contained the full range of essential amino acids. Insignificant differences in the indicators were due to the research methodology and did not go beyond the limits of permissible deviations. The aim of this study was to study the behavior of the protein during processing and to determine its key functional properties for combined meat products containing other proteins of plant origin. Table 1 shows the amino acid composition of the protein of defatted soy flour and its other analogues. Control samples 1 and 3 are traditional soy protein preparations, and samples 2 and 4 are their modified counterparts. The results of the analysis of the amino acid composition indicate that all samples, regardless of the content of other modified proteins, contained the full range of essential amino acids. Insignificant differences in the indicators were due to the research methodology and did not go beyond the limits of permissible deviations. The aim of this study was to study the behavior of the protein during processing and to determine its key functional properties for combined meat products containing other proteins of plant origin.

Results and discussion
The studies were carried out in a wide range of pH depending on the concentration of salts and temperature regimes. The fat-holding capacity of the preparation was 1.0 g oil/g of the preparation for both samples. The value of indicators of solubility, water-holding capacity and critical concentration of protein gelation of the modified soy concentrate is comparable to the same indicators of the protein of soy concentrate produced from local soybean seeds.
When determining the emulsion stability, there was no separation of the emulsions stabilized with samples of soy concentrates. The absence of significant differences in the functional properties of the protein of modified soy protein supplements and exogenous analogues is a confirmation of their identity.
The functional properties of the soy protein supplement (control) and its modified analogue are shown in Table 2. The fat-holding capacity of the preparation was 1.0 g oil/g of the preparation for both samples. The value of indicators of solubility, water-holding capacity and critical concentration of protein gelation of the modified soy concentrate is comparable to the same indicators of the protein of soy concentrate produced from local soybean seeds.
When determining the emulsion stability, there was no separation of the emulsions stabilized with samples of soy concentrates. The absence of significant differences in the functional properties of the protein of modified soy concentrates and exogenous analogues confirms their identity.
Studies have shown that the most effective interaction of vegetable and meat proteins occurs when replacing 25% of the modified soy concentrate [4,7]. This sample was chosen for further research. At the second stage, the objects of study were boiled sausage "Extra" of the 1st grade, in the recipe of which there is no vegetable protein (sample 1 -control), containing a 25% suspension of modified soy concentrate (sample 2).
Analysis of these data allows characterization of samples containing suspensions of modified soy concentrate and soy concentrate as having a high yield and low weight loss during heat treatment. The weight loss rates of the studied minced meats vary from 13% (without vegetable protein preparation) to 11.2% and 11.3% containing suspensions of modified soy concentrate and soy concentrate, respectively.
The value of the output of finished products is one of the criteria that determine the economic feasibility of the production of cooked sausages. At the same time, it is closely related to the functional properties of the mince system proteins, which determine the juiciness of the finished product.
One of these properties is the ability of minced meat to retain bound moisture during heat treatment. In our opinion, water-holding capacity (WHR) and structural-mechanical characteristics are key functional properties for evaluating the quality of cooked sausages.
The water-retaining capacity data indicate that the ability of heat-treated meats to retain moisture does not differ significantly. The VSL of the control sample, the main prescription component of which is beef of the 1st grade, is slightly lower than in samples containing a 25% suspension of modified soy concentrate and a 25% suspension of soy concentrate. These data confirm the previously obtained functional properties of the modified soy concentrate and soy concentrate.
The use of 25% modified soy concentrate in the production of cooked sausages instead of an equivalent amount of raw meat allows you to create a stable emulsion that retains loosely bound moisture when heated. Structural and mechanical properties of sausages were determined on the INSTRON laboratory unit of the city sanitary and epidemiological station.
In a comparative analysis of the indicators in samples 2 and 3 in relation to the control, which does not contain vegetable protein, a change in consistency is observed, which becomes tenderer. This phenomenon is accompanied by a decrease in the shear stress in sample 2. The determination of the cutting work made it possible to note changes in this indicator similarly to the values of the shear force.

Conclusions
The presented data indicate that the introduction of modified soy concentrate and soy concentrate into the stuffing system is accompanied by a decrease in the values of cutting work and shear stress indicators. As a result, the use of highly functional soy preparations leads to a significant improvement in the properties that determine the structural and mechanical characteristics of the combined mince products. The use of 25% modified soy concentrate and soy concentrate in cooked sausages improves texture, increases product yield, and makes the product easy to cut.
Thus, according to the complex of functional properties, all the studied concentrates correspond to soy protein concentrates produced by traditional technology. A characteristic feature of the preparations is the slight dependence of protein solubility on temperature and the content of sodium chloride in solution.
The results of the studies indicate a similar behavior of suspensions of modified soy concentrates and soy concentrates from soybeans of a local variety in the composition of boiled sausages.