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Changes in the muscle tissue microstructure lead to changes in meat quality. One of the causes of the myopathy development is animal stress. Pigs experience the strongest stress during pre-slaughter holding. The study of the postmortem meat structure depending on fasting time is a topical task. The objects of the research were samples of m. L. dorsi obtained after slaughter from pigs that differed in fasting time: 4 (group 1), 8 (group 2), 10 (group 3), 16 (group 4) and 18 (group 5) hours (N = 20, n = 4). Investigation of the microstructure and morphometric measurements were carried out on preparations stained with hematoxylin and eosin. Myopathic changes in muscle tissue were assessed using a semi-quantitative method developed earlier. All studied samples were characterized by the uniform condition of muscle tissue. Statistically significant differences between individual groups were observed regarding the number and area of giant fibers, sarcomere length, diameter of muscle fibers and proportion of muscle fibers, which diameter was lower or higher by 1/3 than the mean fiber diameter. An increase in the pre-slaughter holding time reduced the number and area of giant fibers (r = –0.8437 and –0.5796, respectively), as well as the diameter of “normal” fibers (r = –0.5337), which positively influenced pork quality. Groups 1, 2 and 3 were characterized by the presence of signs of moderate and pronounced myopathy. Only one carcass with pronounced myopathic signs was revealed in each of groups 4 and 5. In group 4, one carcass did not have signs of myopathy. Pre-slaughter holding during 4, 8 and 10 hours led to deterioration of pork quality. The recommended fasting time is 16 hours.

In this article, the proteomic profiles of pork by-products (snout, tongue, liver, kidney, spleen) were studied by comparative method on the first day and the fifth day of their storage. Two-dimensional electrophoresis according to O’Farrell was used for the aims of this article, while the results were further processed in ImageMaster software. Proteomic maps of by-products showed clear changes in protein composition after visualization and images analysis. There was a decrease and increase in manifestation intensity of some proteins. The study of the obtained electrophoregrams with the help of references resources allowed identifying various compounds in the by-products. 9 protein fractions with various intensity of manifestation were found on the day 1st and 5th. On the 1st day the following substances were intensively manifested: in the liver — glutathione peroxidase 4 (22.3 kDa), LEAP-2 (8.8 kDa); in the kidneys — quinone oxidoreductase (34.9 kDa); in the spleen — glycoprotein CD59 (13.7 kDa), in the patch — protein flint (49.07 kDa). It is noted that these proteins play their role in stopping certain processes in cells, like oxidation, microbial activity, and accumulation of toxic substances. These processes can worsen the quality of raw materials, and further lead to spoilage of the food product. On the 5th day of storage the highest intensity of manifestation of glyceraldehyde-3-phosphate dehydrogenase (35.8 kDa) in the liver was observed; superoxide dismutase [Cu-Zn] (15.8 kDa) was noted in the kidneys, colony-stimulating factor (16.2 kDa) was observed in the spleen and glutaredoxin –1 (11.8 kDa) in the tongue. In its turn, on the fifth day these chemical processes manifested themselves more intensely, as the fatty acids and glucose broke down. To obtain more accurate results, the proteins were compared by their volume. Among the identified fractions the highest expression was observed in LEAP 2 (8.8 kDa) on the first day, and in glyceraldehyde-3-phosphate dehydrogenase (35.8 kDa) on the fifth day. The least change in the intensity of manifestation was noted for superoxide dismutase [Cu-Zn] (15.8 kDa), which volume increased during storage by 13% for 5 days. The analysis of the obtained electrophoregrams allowed identifying various compounds, tracing the changes in the qualitative composition of protein in by-products during various periods of their storage. The obtained data demonstrate the transformation of protein molecules during storage, which makes it possible to determine the changes and quality of the food products.

The review paper examines the main risk factors for microbial contamination of meat at different stages of its processing. Particular emphasis has been placed on primary animal processing being the most hazardous in terms of microbial contamination of meat. Carcass cross-contamination most frequently occurs during skinning and evisceration since hides and the digestive tract are the primary sources of microbial pathogens. It is necessary to observe stringent sanitary and hygienic rules when performing these operations. Continuous cold chain management along all following stages of meat processing and control of the sanitary status of cold chambers during meat storage are of extreme importance. An increase in the microbial counts due to the high number of manual operations was observed during meat cutting, boning, and trimming. Subsequent stages of meat processing, including mincing, curing, the addition of spices, also promote significant microbial growth. Strict control regarding detection of dangerous pathogens, especially L. monocytogenes, is needed at this stage. In general, to minimize problems linked with meat and meat product safety, it is necessary to take timely measures on sanitary treatment of meat processing facilities, including the prevention of biofilm formation.

In the present review, we focus on the features of the collagen structure. In particular, we report the correlation between the amount of proline and hydroxyproline and the temperature of denaturation, as well as the changes of collagen structure after thermal treatment. After cooling, denaturated collagen forms dense jellies which may absorb a large amount of water. The influence of pH on the denaturalion temperature, solubility andthe strength characteristics of collagen-containing proteins are described. The review also describes the data on the influence of various food additives and chemicals (acids, alkalis, salts i.a. phosphates, hydrocolloids) on the collagen protein structure and technological properties. The effect of acids, alkalis, salts on the properties of collagen dependson the nature and strength of the ions and their affinity for the collagen ions. The interactions between the collagen proteins and hydrocolloids result in the synergetic effect. Phosphates and collagen form solid structures.

Abstract Use of the prediction technologies is one of the directions of the research work carried out both in Russia and abroad. Meat processing is accompanied by the complex physico-chemical, biochemical and mechanical processes. To predict the behavior of meat raw material during the technological processing, a complex of physico-technological and structural-mechanical indicators, which objectively reflects its quality, is used. Among these indicators are pH value, water binding and fat holding capacities, water activity, adhesiveness, viscosity, plasticity and so on. The paper demonstrates the influence of animal proteins (beef and pork) on the physico-chemical and functional properties before and after thermal treatment of minced meat made from meat raw material with different content of the connective and fat tissues. On the basis of the experimental data, the model (stochastic dependence) parameters linking the quantitative resultant and factor variables were obtained using the regression analysis, and the degree of the correlation with the experimental data was assessed. The maximum allowable levels of meat raw material replacement with animal proteins (beef and pork) were established by the methods of mathematical programming. Use of the information technologies will significantly reduce the costs of the experimental search and substantiation of the optimal level of replacement of meat raw material with animal proteins (beef, pork), and will also allow establishing a relationship of product quality indicators with quantity and quality of minced meat ingredients.