COMPARATIVE DYNAMICS OF PROTEIN DESTRuCTION IN CANNED FOODS IN SAuCE AT DIFFERENT THERMAL TREATMENT REGIMES AND SuBSEquENT

In the course of investigations, the structural changes in proteins were established, which were associated with the preliminary treatment of meat ingredients, a pH level of the system and parameters of thermal treatment. The pasteurization regimes allowed retaining a protein nitrogen proportion up to 94% by the end of canned food storage duration. Upon sterilization, the losses in protein nitrogen were two times higher. A negative effect of more acidic sauce on preservation of the protein nitrogen fraction in canned foods was established. An accumulation of the peptide nitrogen fraction in the canned foods in tomato sauce after pasteurization was two times more intensive. In the sterilized canned foods, the processes of accumulation of the low molecular weight nitrogenous compounds were more intensive, which suggests a depth of destruction of the protein and peptide nitrogen fraction. It was shown that an accumulation of amino-ammonia nitrogen during canned food storage was on average 12.4% irrespective of the pH value in the used sauces and the type of thermal treatment. A shift in the pH value of the canned foods toward the acid side upon pasteurization was noticed. With that, a degree of the shift in the canned foods in tomato sauce was 2.5 times higher than the pH value of the canned foods in sour cream sauce. When sterilizing canned foods, another dynamics of the pH values was observed: a pH value declined by 0.39 units in the canned foods in tomato sauce and grew by 0.22 units in the canned foods in sour cream sauce. During storage, the tendency of more intense pH decline was revealed for the canned foods in tomato sauce after pasteurization compared to the canned foods after sterilization. Another character of the pH value dynamics was found in the canned foods in sour cream sauce: an insignificant increase (by 0.7%) of the pH value in the pasteurized canned foods and a significant decrease (by 8.4%) in the sterilized canned foods were observed by the end of storage. Аннотация На предприятиях мясной промышленности, где осу В ходе исследований установлены структурные изменения белков, связанные как с предварительной обработкой мясных ингредиентов, уровнем рН системы, так и с параметрами тепловой обработки. Режимы пастеризации позволили сохранить долю белкового азота до 94% к концу срока хранения консервов. При стерилизации потери белкового азота в 2 раза выше. Установлено отрицательное действие более кислого соуса на сохранность белковой фракции азота консервов. Накопление пептидной фракции азота в  консервах в  томатном соусе после пастеризации в  2 раза интенсивнее. В  стерилизованных консервах интенсивнее процессы накопления низкомолекулярных азотистых соединений, что свидетельствует о глубине деструкции белковой и пептидной фракции азота. Показано, что накопление амино-амиачного азота в процессе хранения консервов в среднем составило 12,4% вне зависимости от рН используемых соусов и  вида тепловой обработки. Отмечено смещение величины рН консервов в кислую сторону при пастеризации, причем степень смещения в консервах томатном соусе в 2,5 раза выше по отношению к величине рН для консервов в сметанном соусе. При стерилизации консервов имела место иная динамика величин рН: в консервах в томатном соусе величина рН снизилась на 0,39 единицы, а  в консервах в  сметанном соусе выросла на 0,22 единицы. В процессе хранения выявлена тенденция более интенсивного снижения рН в консервах в томатном соусе после пастеризации по отношению к  консервам, подвергшихся стерилизации. Иной характер динамики величины рН в консервах в  сметанном соусе: отмечено не значительное, на 0,7%, увеличение рН к  концу срока хранения в  пастеризованных консервах и  значительное снижение, на 8,4%, в  стерилизованных консервах. уДК/uDC: 664.9 DOI 10.21323/2414-438X-2017-2-1-37-46

In the course of investigations, the structural changes in proteins were established, which were associated with the preliminary treatment of meat ingredients, a pH level of the system and parameters of thermal treatment.The pasteurization regimes allowed retaining a protein nitrogen proportion up to 94% by the end of canned food storage duration.Upon sterilization, the losses in protein nitrogen were two times higher.A negative effect of more acidic sauce on preservation of the protein nitrogen fraction in canned foods was established.An accumulation of the peptide nitrogen fraction in the canned foods in tomato sauce after pasteurization was two times more intensive.In the sterilized canned foods, the processes of accumulation of the low molecular weight nitrogenous compounds were more intensive, which suggests a depth of destruction of the protein and peptide nitrogen fraction.It was shown that an accumulation of amino-ammonia nitrogen during canned food storage was on average 12.4% irrespective of the pH value in the used sauces and the type of thermal treatment.A shift in the pH value of the canned foods toward the acid side upon pasteurization was noticed.With that, a degree of the shift in the canned foods in tomato sauce was 2.5 times higher than the pH value of the canned foods in sour cream sauce.When sterilizing canned foods, another dynamics of the pH values was observed: a pH value declined by 0.39 units in the canned foods in tomato sauce and grew by 0.22 units in the canned foods in sour cream sauce.During storage, the tendency of more intense pH decline was revealed for the canned foods in tomato sauce after pasteurization compared to the canned foods after sterilization.Another character of the pH value dynamics was found in the canned foods in sour cream sauce: an insignificant increase (by 0.7%) of the pH value in the pasteurized canned foods and a significant decrease (by 8.4%) in the sterilized canned foods were observed by the end of storage.
ment can be the data on a decrease in the content of vitamin B1 by 50% and B2 by 52.7% in the sterilized pates [2].It is known that changes in proteins have a diverse character and depend on a thermal treatment temperature, its duration, a meat type, a method of preliminary treatment of ingredients and so on.Studies in this scientific direction were begun in the 1950s.V.N.Orekhovich [3] and V.A. Belitser [4] regarded protein denaturation as a complex process of molecular disintegration on constituents, i.e., the denaturation process represented a process of disorganization of the protein molecular structure; as a result, they became looser and open to an influence of other factors.E.V. Jensen et al. [5] suggested that in the process of protein aggregation and coagulation at thermal treatment, the bonds between molecules existed due to the bonds formed between the carboxyl groups and amino groups of adjacent polypeptide chains.It is known that temperatures, at which denaturation of different meat protein fractions occurs, are significantly different.For example, denaturation of globular proteins (actin, myosin, actomyosin) began at a temperature of 45-50 °С, and at a temperature of 60 °С, about 90% of protein molecules underwent the process [6].Albumin was completely denatured at 60 °С, and at 70-80 °С, all muscle proteins were denatured.Due to partial hydrolytic breakdown of proteins, the number of free NH2-and СООН-groups increased and a coagulation process that developed at their specific concentration was characterized by a steady decrease in the number of free NH2-and СООН-groups [7][8][9][10].
The main share in the market of various assortment groups of canned foods is occupied by sterilized canned foods.Up to date, we have quite comprehensively studied the character of protein, fat and polysaccharide transformation in meat and meat-and-plant canned foods upon their production [11][12][13][14].Currently, a topical task is the development of gentle regimes of scientifically substantiated technology for canned food thermal treatment, which will allow a producer to manufacture products with high organoleptic and physico-chemical indicators and, at the same time, significantly reduce energy consumption in production.The earlier research showed that the development of rational sterilization regimes for canned beef in pieces led to a very insignificant reduction in the mass fractions of essential and non-essential amino acids (by 4.4-5.3%)and an increase in amino-ammonia nitrogen (by 1.6%) [15].Therefore, a pasteurization process of canned foods can be effectively used as a gentle thermal treatment.
В работе использованы следующие методы определения: -величины рН -методом измерения разности электрических потенциалов между стеклянным электродом и электродом сравнения, помещенными в образец продукта; -содержания амино-аммиачного азота (ААА), основанным на связывании аминогрупп и аммиака Comprehensive studies on pasteurized canned meat technologies were carried out at the beginning of the 1990s and included a narrow canned food range, namely, ham products.Taking into consideration an increasing trend towards manufacturing foods that are stable in terms of the nutritive and biological value, underwent minimal thermal treatment and retained high organoleptic characteristics, studies on improvement of a technology for canned dinner dishes with meat and sauce are becoming more and more important.
The aim of the present work is to study the comparative dynamics of protein destructive changes in the pasteurized and sterilized canned foods "Meat in sauce" in production and during storage.

Materials and methods
The subjects of the research were the experimental samples of canned foods "Meat in sauce": 1PCF -pasteurized canned foods "Meat in tomato sauce"; 1SCF -sterilized canned foods "Meat in tomato sauce"; 2PCF -pasteurized canned foods "Meat in sour cream sauce"; 2SCF -sterilized canned foods "Meat in sour cream sauce".
The canned foods were made from preliminarily roasted beef with a mass fraction of the fatty and connective tissues not more than 14% and cut into pieces with a weight of 30-50 g.Mass fractions of meat and sauce were 40% and 60%, respectively.The tomato sauce included sauteed carrot and onion, parsley root, tomato paste, wheat flour, sesame seeds, table salt, granulated sugar, powdered black pepper and water.The sour cream sauce included sour cream, wheat flour, table salt, powdered black pepper, powdered nutmeg and water.Canned foods were produced in a polymer container with a weight of 140 g under two experimental regimes with the same duration of the pasteurization and sterilization stages: -1 regime: pasteurization at a temperature of 100 °С; -2 regime: sterilization at a temperature of 120 °С.
Sauces used in production of the canned food samples under investigation differed in the pH values: рН=4.4 (the tomato sauce), and рН=5.0 (the sour cream sauce).
formaldehyde in the neutral environment with the following titration with alkaline of the carboxyl groups, which quantity is equivalent to the quantity of free amino acids; -nitrogen fraction content -the methods based on the ability of the protein substances to precipitate under the action of different reagents.Protein nitrogen was precipitated with trichloroacetic acid with the following mineralization of a precipitate and detection of nitrogen by the Kjeldahl method.Peptide nitrogen was determined by the difference between nitrogen precipitated with phospho-wolframic acid and nitrogen precipitated with trichloroacetic acid.An amount of residual nitrogen is the difference between an amount of the total nitrogen and an amount of protein and peptide nitrogen.
The experimental data were processed by the methods of mathematical statistics.The experiment was carried out in triplicate.The hypotheses were verified with probability of 0.95.
Approximation of the experimental data was carried out in MS Excel by building a graph with the subsequent selection of a suitable approximating function.

Results and discussions
Changes in the physico-chemical indicators of products including a pH value occur in the process of canned food thermal treatment and subsequent structural changes in proteins, disruptions of the initial and formation of new bonds with participation of the hydrogen bonds, sulfhydryl, disulfide, acidic and basic protein groups and hydrophobic interactions.The dynamics of the pH values after production and during storage of the canned foods is given in Fig. 1.
The canned food recipe mixtures prepared for filling into containers had the following pH values before thermal treatment: 5.72 in "Meat in tomato sauce" and 5.86 in "Meat in sour cream sauce".
It is known that a degree of heat denaturation effect on constituents of a product nutritive value depends on conditions of thermal treatment.For example, canned food pasteurization led to a shift in the pH value toward the acid side with a shift degree 2.5 times more intensive in the canned foods in tomato sauce compared to the canned foods in sour cream sauce.Another dynamics of the pH values was observed upon canned food sterilization: in the canned foods in tomato sauce, the pH value declined by 0.39 units and in the canned foods in sour cream sauce it increased by 0.22 units.It can be suggested that this was associated with a different degree of an increase in free NH 2and СООН-groups upon pasteurization and sterilization of the canned foods with different initial pH values.
During storage, the pH values of canned foods somewhat stabilized and after 15 months were: -5.43 in the pasteurized canned foods "Meat in tomato sauce", which was 3.4% lower compared to the corresponding value immediately after pasteurization; -5.29 in the sterilized canned foods "Meat in tomato sauce", which was 0.75% lower compared to the values after production; -5.86 in the pasteurized canned foods "Meat in sour cream sauce", which was 0.7% higher compared to the value immediately after pasteurization; -5.57 in the sterilized canned foods "Meat in sour cream sauce", which was 8.4% lower compared to the corresponding values after production.Fig. 2 and 3 present the curves for changes in the content of nitrogenic substance fractions in a product after production and during storage.Analysis of the obtained data showed a presence of the destructive changes in the protein constituent of the pasteurized and sterilized canned foods after production and during storage.With that, an intensity of the total nitrogen loss at higher temperatures corresponds to the data of A.A. Sokolov and M. Kemal [16], who pointed out that a degree of changes in the total nitrogen content in meat increased in the canned foods with the rise of temperature and heating duration.
An impact of the pasteurization temperature and subsequent storage of the studied canned foods for 15 months reduced the mass fraction of total nitrogen on average by 5%.These changes in the total nitrogen content are in a range of an experiment error, especially, taking into consideration the heterogeneity of the ratio of tissue types in meat pieces.A decrease in the total nitrogen mass fraction in the canned foods that underwent sterilization was on average 6.6%.
A tendency towards a reduction in the protein nitrogen content was observed, which was associated, among other things, with preliminary short-term roasting of meat raw material.A decrease in the level of protein nitrogen in the pasteurized canned foods was less evident and was on average 5.2% after storage for 15 months relative to the data after pasteurization.For sterilized canned foods, the average values of this indicator were two times higher, i.e., a reduction in protein nitrogen was 10.1%.experiment error, especially, taking into consideration the heterogeneity of the ratio of tissue types in meat pieces.A decrease in the total nitrogen mass fraction in the canned foods that underwent sterilization was on average 6.6%.
A tendency towards a reduction in the protein nitrogen content was observed, which was associated, among other things, with preliminary short-term roasting of meat raw material.A decrease in the level of protein nitrogen in the pasteurized canned foods was less evident and was on average 5.2% after storage for 15 months relative to the data after pasteurization.For sterilized canned foods, the average values of this indicator were two times higher, i.e., a reduction in protein nitrogen was 10.1%.
The dynamics of the peptide nitrogen accumulation was also different in the pasteurized and sterilized canned foods.For example, in the canned foods in tomato sauce after pasteurization, an accumulation of the peptide nitrogen fraction was twice as intensive as in the same canned foods but underwent sterilization.At the same time, an accumulation of the low molecular weight nitrogenous y = -0,4183x 5 + 8,9447x 4

6
experiment error, especially, taking into consi ratio of tissue types in meat pieces.A decrease in the canned foods that underwent sterilization A tendency towards a reduction in th observed, which was associated, among other t roasting of meat raw material.A decrease in th pasteurized canned foods was less evident and for 15 months relative to the data after pasteuriz the average values of this indicator were two protein nitrogen was 10.1%.
The dynamics of the peptide nitrogen acc pasteurized and sterilized canned foods.For tomato sauce after pasteurization, an accumulati was twice as intensive as in the same canned fo the same time, an accumulation of the low R y = -0,356x 5 + 7,9576x 4  % to non-protein compounds was higher in the same samples but sterilized.Similar dynamics was observed in the canned foods in sour cream sauce (Fig. 2-3).The obtained data fully corresponds to the data of A.A. Sokolov [17,18]: with temperature rise and storage duration extension, the rate of polypeptide breakdown increases much more intensive than the rate of protein substance breakdown.
The destruction processes persisted during storage of the pasteurized canned foods; with that, a degree of manifestation of protein destruction depended on the pH value of the used sauce (Fig. 2-3).For example, for the canned foods "Meat in tomato sauce", three storage periods can be distinguished: -the first period (up to 6 th month of storage) was characterized by a decrease in the peptide mass fraction by 14.2% due to destruction of raw material peptides and peptides formed in thermal treatment of the canned foods, with the growth in the residual nitrogen fraction at the equal quantity; -the second period (from the 6 th to 9 th month of storage) was marked by the growth in the mass fraction of peptide nitrogen by 11.3% due to destruction of the protein constituent of the canned foods with a decrease in the residual nitrogen proportion at the equal quantity; -the third period (from the 9 th to 15 th month) was characterized by steady destruction of the peptide nitrogen fraction by 15.1% and a corresponding increase in the mass fraction of residual nitrogen.
In the canned foods "Meat in sour cream sauce", two periods were noticed: -the first period (up to 6 th month of storage) was characterized by an increase in the mass fraction of peptide nitrogen by 14.9% due to destruction of the protein constituent of the canned foods with a decrease in the residual nitrogen proportion at the equal quantity; -the second period (from the 6 th to 9 th month of storage) was marked by the growth in the mass fraction of peptide nitrogen by 10.5% due to its deep destruction with an increase in the residual nitrogen fraction at the equal quantity.
During storage of the sterilized canned foods, two principally different periods were noticed in the dynamics of the peptide and residual nitrogen fractions: the first period up to 6 th month and the second period from the 6 th to 15 th month.For the canned foods "Meat in tomato sauce", the first period was characterized by a 19.1% increase in the mass fraction of peptide nitrogen due to the destruction processes in the protein constituent of the canned foods with a decrease in the residual nitrogen fraction at the сервах «Мясо в сметанном соусе» было отмечено снижение на 8,7% доли фракции пептидного азота за счет его разрушения при повышении в равном количестве остаточной фракции азота.Таким образом, было отмечено отрицательное действие более кислого соуса на сохранность белковой фракции азота консервов.
The second period (from the 6 th to 15 th month) was characterized by a retardation of the destructive changes in the peptide and residual nitrogen fractions both in the pasteurized and sterilized canned foods.A degree of changes in mass fractions were ± 0.6% and ±4.1%, respectively.
A value of the determination coefficient is a main criterion for assessing quality of linear and non-linear models.Fig. 1-3 present the regression equations for studied values with the determination coefficient higher than 80%, which allows regarding the obtained dependencies as quite precise (a correlation coefficient exceeds 90%).
Formation of amino compounds and ammonia bases at thermal treatment of canned foods is associated with deamination and decarboxylation of amino acids -both free and partially existing in the composition of proteins and polypeptides, while accumulation of hydrogen sulphide is a result of breakdown of sulfur-containing amino acids.It is obvious that a thermally treated product has higher quality when the content of ammonia, hydrogen sulphide and carbon dioxide is lower.However, as their initial content in meat can be different, their absolute content after pasteurization or sterilization cannot be used for making a conclusion about qualitative changes in a product.free and partially existing in the composition of proteins and polypeptides, while accumulation of hydrogen sulphide is a result of breakdown of sulfur-containing amino acids.It is obvious that a thermally treated product has higher quality when the content of ammonia, hydrogen sulphide and carbon dioxide is lower.However, as their initial content in meat can be different, their absolute content after pasteurization or sterilization cannot be used for making a conclusion about qualitative changes in a product.A dynamics of amino-ammonia nitrogen during canned food storage seems to be more important.The obtained results showed that an impact of pasteurization or sterilization on the protein constituent of the canned foods as seen in the example of amino-ammonia nitrogen after production is hardly distinguishable.During storage, an accumulation of amino-ammonia nitrogen was 12.4% irrespective of pH in the used sauces and thermal burdens (Fig. 4).y = -0,3226x 6 + 7,4871x 5 -67,724x 4 + 302,26x 3 -694,15x 2 + 770,46x -266 R² = 1 y = -0,4906x 6 + 11,42x free and partially existing in the composition of p accumulation of hydrogen sulphide is a result of amino acids.It is obvious that a thermally treated p the content of ammonia, hydrogen sulphide and car as their initial content in meat can be differen pasteurization or sterilization cannot be used fo qualitative changes in a product.A dynamics of a canned food storage seems to be more important.T an impact of pasteurization or sterilization on the p foods as seen in the example of amino-ammonia ni distinguishable.During storage, an accumulation o 12.4% irrespective of pH in the used sauces and the y = -0,3226x 6 + 7,4871x 5  Из-за недостаточности исследований влияния пастеризации, ее продолжительности и интенсивности на динамику содержания общего и амино-аммиачного азота в консервах разных ассортиментных групп делать выводы о том, чем обусловлено разрушение азотистых соединений или образование низкомолекулярных соединений преждевременно.Следовательно, продолжение изучения вопроса в этом направлении актуально.
A dynamics of amino-ammonia nitrogen during canned food storage seems to be more important.The obtained results showed that an impact of pasteurization or sterilization on the protein constituent of the canned foods as seen in the example of amino-ammonia nitrogen after production is hardly distinguishable.During storage, an accumulation of amino-ammonia nitrogen was 12.4% irrespective of pH in the used sauces and thermal burdens (Fig. 4).
The determination coefficient equal to 1 as shown in Fig. 4 means that the dynamics of a variable is precisely described by the obtained models.

Conclusions
During investigation of the destructive changes in proteins of the canned foods in sauce at different types of thermal treatment and subsequent storage, we established that: -an action of pasteurization temperatures caused an inverse relationship of the dynamics of peptide and residual nitrogen fractions in the canned foods irrespective of the system pH; -changes in the pasteurized canned foods were more dynamic, which was apparently associated with the presence of residual microflora that had the proteolytic properties but did not cause deep protein hydrolysis; -an action of sterilization temperatures resulted in deeper destructive changes in protein of the canned foods not only in production but also during storage; the destruction dynamics did not have boundary values, the processes occurred steadily.Due to insufficient investigations of a pasteurization impact, its duration and intensity on the dynamics of the content of total and amino-ammonia nitrogen in canned foods of different assortment groups, it is too early to make conclusions about the causes of destruction of nitrogenous compounds or formation of low molecular weight compounds.Therefore, the further investigation of this question is topical.