Resource-saving technology of animal fats production: scientific and practical approaches and technological advantages

. Specificity of technological cycle of processing of fat raw materials of animal origin lies in the fact that in the process it is possible to receive not only the main commodity product in the form of melted fat, but also secondary products of production, which include unique and valuable in their properties biologically active substances. The present work is devoted to the development of technology of complex processing of fat raw material, by the example of raw fat of ostrich, which allows to increase the fat yield and minimize production waste. The objects of research were: melted fat of ostrich and products of its processing (greaves and protein hydrolysate), obtained by melting in water (control) and catholite under given conditions and parameters. It is shown that fat melted in catholite is characterized by low values of acid, peroxide and anisidine numbers in comparison with the control. It is established that at processing of fat in catholyte its yield even at the temperature of 55°C was over 64.0%, and at heating up to 100°C - 86.6%. It is argued that realization of repeated melt-out, stipulated by technological solutions, reduces risks of formation of significant amount of fat and protein wastes. It is determined that at repeated consecutive melting of protein fraction with temperature increase up to 75°С and 100°С the percentage of fat yield increases by 11.6 and 19.5 %, respectively. The established dependencies formed the basis for the creation of a technological line for processing of fat raw materials. It is proved that the developed technology of ostrich fat extraction with replacement of aqueous phase by catholyte in the process of fat extraction


Introduction
The tasks that face the food and processing industries of the domestic industry include the development of the concept of "resource saving -resource supply", based on the development of environmentally safe waste-free industry, aimed at the transition to industrial reproduction of raw materials.At the same time, an integral part of this process is obtaining new products characterized by high quality indicators.
To obtain animal fats one traditionally uses melting, which is carried out by wet and dry methods.Fat extraction using chemical reagents, hot water and steam, separation, pressing, enzymatic, chemical, electric pulse and vibration methods are also known [1].
In recent years, information and research in the field of processing of fat raw materials of animal origin have been significantly expanded: resource-saving technologies and technical means have been introduced [1][2][3][4][5].It should be noted that new scientific directions are also successfully developed, for example, concerning the use of electrochemically activated liquid in food production, in particular, in the field of fats and oils processing [5][6][7][8][9].At the same time, the issues of their rational use and creation of fundamentally new methods of raw fat processing, allowing to obtain products with specified properties, continue to be significant and relevant.
The aim of the work is to develop a technology for processing raw fat, by the example of raw fat of ostrich, which allows to increase the fat yield and minimize production waste.

Objects and methods of research
The objects of research were: ostrich fat and products of its processing, obtained by wet melting in water (control) and electroactivated liquid (catholite) under given conditions and parameters.In the work, generally accepted methods in the industry were used to control the quality of the obtained fat and greaves.The yield of ghee and greaves was determined in % to the weight of raw fat.To determine the shelf life of ostrich fat, the method of accelerated storage was used according to the Manual on methods of research, technochemical control and production accounting in the oil and fat industry edited by V.P. Rzhekhin and A.G. Sergeev.For this purpose, the fat was placed in a special multi-cell apparatus (E.H. Sargent, and Co., U.S.A.), in which a constant temperature of the oxidized sample was automatically maintained.The air flow rate was measured using a rheometer.The studies were carried out in 3-fold repetition, the data were processed statically using StatSoft Statistical 6.0 programs.
The technology of fat raw material processing included the following sequence of operations: pre-cleaned and washed in anolyte raw fat was subjected to grinding to particle size 3-5 mm and sent to the furnace, where it was heated by acute steam to a given temperature with constant stirring; at the same time in the digester in the ratio of 4:1 to the mass of raw material came previously prepared solution of sodium chloride, passed electrolysis (catholyte).Melting was carried out at temperatures of 55°C, 75°C and 100°C, the duration of the process was 20 minutes regardless of the temperature of raw material processing.The resulting water-protein-fat fraction was ground to form a fine emulsion and further separated into fat-water and water-protein fractions.The fat from the aqueousprotein phase was separated by centrifugation at 6000 rpm.Electroactivated liquid was obtained in an electrolyzer by electrolysis of 4.0% aqueous NaCl solution at a constant current strength of 0.5-0.6A and current voltage of 40-42 V.The catholyte was characterized by the following parameters: pH 9-11, redox potential (ORP) (-600) -(-700) mV (patent for invention No. 2683559 RU, publ.on March 28, 2019) [6].The wet method of fat melting in water was chosen as a control.

Results and Discussion
As it is known, the formation of the quality of the finished product and its yield, which is taken into account in the development of any technology, including fat extraction, is significantly affected by the qualitative characteristics of the initial raw material, technological conditions and parameters of fat extraction.
In the course of research, it was established that by the index of iodine number (J2 of subcutaneous fat -56.68 g/100g, internal -61.7 g/100g) ostrich fat exceeds the fats of farm animals and is close to chicken fat.The obtained data indicate the prevalence of unsaturated fatty acids in its composition and confirm the feasibility of multifunctional use of ostrich fat.The established low melting and solidification temperatures of ostrich fat confirm its easy melting, which is an important technological advantage.Calculation of energy value showed that for 100 g of ostrich fat it is equal to 806.6 Kcal, which indicates wide prospects for its use in various industries.
Further, in accordance with the above-described methodology, the selected fat raw material for disinfection and purification from contaminants was thoroughly washed using the obtained anolyte with pH 3-4 and ORP (16.7) -(24.9)(Table 1).According to the obtained data (Table 2), the use of anolyte with low acidity contributes to the reduction of microbiological contamination of raw fat.Thus, after treatment, the total microbial number decreased for samples of internal and subcutaneous fat, respectively, 185 and 160 times, which confirms the feasibility of using anolyte for disinfection of raw fat.It should be noted that E. coli bacteria, molds and pathogenic microorganisms, including salmonella, were not detected in raw fat both before and after anolyte treatment.
In the course of organoleptic quality assessment, it was found that the fat obtained by melting in water as well as in catholyte met the requirements of the normative documentation.However, when melted in water, especially at low-temperature treatment (55°C), the fat was characterized by a pronounced specific odor without signs of siltation, unlike the experimental samples.As can be seen from the data in Table 2, ostrich fat has low values of acid, peroxide and anisidine numbers.According to the indicators of physicochemical properties of fat obtained by melting in water and catholite, we can judge about the advantages of the proposed technology.In the course of the research the change of viscosity was recorded not only from temperature, but also from pH of the medium in which the fat was melted.Apparently, it is connected with the influence of ECA medium weakening the bonds between lipid molecules.
It was found that when introducing catholyte in the process of wet melting, the yield of melted fat was over 64.0% even at low temperature of raw material processing (55°C), and at heating up to 100°C the yield was 86.6%.The use of ECA medium leads to partial destruction of lyophobic sites of micelle molecules and, as a consequence, to irreversible destruction of the solvate shell of fat cell, accompanied by separation of phosphoric acid residue from diglyceride.The colloidal particles freed from the stabilizing shell aggregate and are released on the surface [11].Denaturation of protein structures under the action of ECA medium is also important, which is caused not only by temperature and mechanical effects, but also by high biological and physicochemical activities of the catholyte.In this regard, the use of activated liquid as a potential source of intensification of chemical reactions in fat production can rightfully compete with traditionally used methods [12][13].
The obtained new knowledge formed the basis for the creation of a complex environmentally safe technological line for processing of fat raw materials (Figure 1) [13].As it is known, the efficiency of technology and production line of fat obtaining depends not only on the quality of clarified fat and its yield, but also on the properties of secondary products of its processing (Table 3).
The highest greaves yield was recorded at the melting temperature of 55°C.However, the possibility of repeated melting (Figure 1), provided by technological solutions in the line reduces the risk of formation of a significant amount of fat and protein waste.For this purpose, the proposed line (Figure 1) provides the possibility of staged melting with preservation of the sequence of technological operations, except for the stage of fat raw E3S Web of Conferences 463, 01023 (2023) EESTE2023 https://doi.org/10.1051/e3sconf/202346301023material processing in the screw inactivator (Item 2) and the subsequent return of the protein phase from the centrifuge (Item 6) for repeated melting.After dividing the suspension in the centrifuge into two phases from its first output protein phase -goes to the hopper (Item 4) and screw elevator transported to the screw inactivator (Item 2) for repeated fat melting at a given temperature, and the remaining fat-water phase through the second output of the centrifuge (Item 6) is transferred to a vertically mounted tank (Item 7) for further processing.Thus, in the course of research it was found that the repeated consecutive melting with increasing the temperature to 75°C and 100°C was able to increase the fat yield by another 11.6 and 19.5%, respectively.The obtained values of the mass fraction of dry matter in the water-protein phase (from 1.4% to 2.0%) prove the fact of thermochemical deformation of the protein molecule in the ECA medium, the nature and strength of the energy effect of which caused the rupture of intermolecular bonds of the protein part of fat.It should be noted that when fat was melted in water, this index was only from 0.2% to 1.0%.That is, unlike water, the mechanism of action of catholyte is connected with the specificity of charge distribution and electrostatic potential of protein molecule in it.This increases the degree of protein hydration, adsorption on the surface of fat particles, and thus increases its emulsifying ability.The proposed model of interaction of ions of ECA medium with protein structure agrees with the results of a number of scientific works [14][15][16][17].

Conclusion
Summarizing the above, it should be noted that the totality of the proposed technological solutions creates advantages for planning and selection of full or staged fat melting depending on the specified physical and chemical parameters and the intended purpose of the product.Additionally, the installed equipment contributes to minimizing the waste of valuable fat and protein resources, and the use of environmentally safe component of sodium chloride will not have a negative impact on the natural environment.In addition, an important fact is that the developed line of complex processing of raw fat of ostrich is also applicable for easily digestible animal fats, as the research has established the proximity of ostrich fat to easily digestible poultry fats [1,12].This fact gives the basis to recommend the developed technological solutions for the use of ECA medium in the process of melting for other fats of agricultural poultry.
the Ministry of Science and Higher Education of the Russian Federation (Agreement N 075-15-2021-679).

Table 1 .
Microbiological contamination of ostrich raw fat.

Table 3 .
Yield of fat-and protein-containing products at catholite melting.