The expediency and prospects of using secondary fish raw materials from silver carp in the structuring agents technology have been substantiated. The combination of secondary fish raw materials and seaweed with different mechanisms of gelation has a targeted effect on the organoleptic, structural-mechanical, and physicochemical properties of food products. Accordingly, the expediency of adding the Black Sea alga cystoseira (2%) to optimize the mineral composition of the structuring agents and increase their jelly-making properties was established. Using experimental studies and multicriteria optimization, the optimal ratio of secondary fish raw materials – 40%; water – 60% and rational heat treatment – 150 min, at a temperature of 85 – 100 °C has been determined. An analysis and comparison of various preservation methods have confirmed the expediency of using the freeze-drying method of drying fish broths for the production of structuring agents, which allows to preserve of the original properties of the product, biologically active substances, reduce the mass of the dried product and increase the shelf life of the structuring agents. The optimal storage conditions have been determined – the ready-made structuring agents were packed in three-layer paper kraft bags and stored in a cool dry place at a temperature of 22 ±2 °C and relative humidity of no more than 70% for 12 months. It was found that the physical and chemical indicators of the structuring agents depend on the features of the structure, amino acid composition of fish collagen. The presence of the overwhelming number of high-molecular-weight molecules in the composition of the structuring agents and the preservation of the native structure determine high indicators of dynamic viscosity, dissolution time, and strength. As a result of the research, it was revealed that the high protein content largely depends on the amount of collagen in the secondary fish raw material, which has a positive effect on the gelling properties of the product being created.
The natural and climatic conditions and significant resource potential of Ukraine contribute to the development of fisheries in their freshwater reservoirs. The production of commercial fish in domestic aquaculture farms is 23 thousand tons, of which 60% is silver carp (
Accordingly, an important task of fish processing enterprises in Ukraine is to ensure and increase the efficiency of using the resource potential of the domestic fishery complex, possibly under the condition of rational use of fish from own water reservoirs of the country (
One of the main ways of efficient use of fish resources is the processing of secondary fish raw materials left after their processing. About a third of secondary fish raw materials from silver carp are heads, bones, and fins, which are a valuable source of proteins, primarily collagen, and are widely used in the food industry (
A promising direction in the processing of collagen-containing secondary fish raw materials from silver carp is the production of structuring agents. Monitoring of modern trends in the market for structuring agents testifies to their limited assortment based on domestic raw materials, the most common of which is gelatin. However, due to massive cases of cattle diseases, the use of collagen of animal origin is dangerous (
A great contribution to the solution of the problem of complex fish processing and production of structuring agents were made by scientists
However, there are no conceptual developments in the direction of the study of consumer properties of structuring agents based on secondary fish raw materials from the most common object of aquaculture in Ukraine – silver carp, which determines the relevance and practical importance of scientific research.
The hypothesis of the research work was based on the assumption that the combination of protein (heads, bones, fins of silver carp) and polysaccharide (cystoseira alga) structuring agents improves the organoleptic characteristics of food products, increases the water-holding capacity, and allows to create products with a predictable complex of consumer properties. According to the results obtained, it was confirmed that the combination of structuring agents of various natures makes it possible to more accurately regulate the consistency of the product, purposefully affects the structural-mechanical and physicochemical properties of food products through the use of raw materials with various mechanisms of gelation.
Research of structuring agents for control and experimental samples (packed edible gelatin, grade P-7, manufactured by the Lysychansk Gelatin Plant; structuring agents based on secondary fish raw materials; structuring agents based on secondary fish raw materials with the addition of the Black Sea algae cystoseira) were carried out using the following raw materials: heads, bones, and fins of freshwater herbivorous fish – silver carp (
Silver carp.
Calcium chloride, CaCl2. (AGROZONE Ukraine).
Hydrochloric acid, HCl (grade A, analytical grade, LLC “Khimlaborreaktyv” Ukraine).
Sodium hydroxide, NaOH (grade A, analytical grade, LLC “Khimlaborreaktyv” Ukraine).
Sulfuric acid, H2SO4 (grade A, chemically pure, LLC “Khimlaborreaktyv” Ukraine).
The studies used variegated silver carp weighing 2 – 2.5 kg, 50 – 60 cm long, autumn catch, which was grown at the Irkliivskyi fish farm of herbivorous fish. Conducted studies of the structural and morphological composition of experimental groups (heads, internal organs, carcasses, fillets, scales, fins, bones), calculated the proportion of edible and inedible parts.
Drying cabinet (SNOL, LLC “Labimpex LTD” Ukraine).
Muffle furnace (SNOL, LLC “Labimpex LTD” Ukraine).
Automatic amino acid analyzer (T 339 produced by “Mikrotekhna” Czech Republic).
Atomic absorption spectrophotometer (Shimadzu AA-6200, LLC “SPEKTROLAB” Ukraine).
Fat analyzer (SOX 406, LLC “Khimlaborreaktyv” China).
Gas chromatograph (“Kupol-55”, “Shimadzu Corporation” Japan).
Program viscometer (Brookfield LVDV-II+PRO USA), pH meter HI8314 HANNA (“SPECTRO LAB” Ukraine).
The study of the chemical composition of the structuring agents was carried out according to the following methods: mass fraction of moisture by drying a sample of the product to constant mass at a temperature of 100 – 105 °C according to
The amino acid composition of proteins was determined by ion-exchange liquid column chromatography on an automatic amino acid analyzer T 339 using an LG ANB cation exchange resin (
The mineral composition was determined by inductive plasma atomic emission spectrometry according to
The study of physical and chemical indicators was carried out according to the following methods: transparency – according to own patented method (Patent No. 73282, 2012) on a universal computing device; strength – by the method of establishing the maximum load required for the destruction of the gelatin surface following
Structuring agents.
The statistical analysis data were produced by Microsoft excel and Statistica 15. The accuracy of the obtained experimental data was determined using the Student’s test for a confidence probability of ≤0.05 based on the number of parallel determinations at least 5. Linear programming problems were solved using the MS Excel spreadsheet processor “Search for a solution” setting (Excel Solver).
Structuring agents experimental samples were evaluated according to the following physicochemical parameters: dissolution time, active acidity, dynamic viscosity, gelatin strength, gelatin melting point, solution transparency (Table
Physical and chemical quality indicators of structuring agents.
Indicators | Control | Structuring agents based on | |
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secondary fish raw materials | secondary fish raw materials and cystoseira | ||
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Dissolution time, min. | 12 ±0.6 | 5 ±0.2 | 6 ±0.3 |
Dynamic viscosity, mPa·s-1 | 16 ±0.8 | 17 ±0.7 | 18 ±0.9 |
Gelatine strength, H | 10 ±0.5 | 10 ±0.5 | 11 ±0.5 |
Solution transparency,% | 28 ±1.4 | 32 ±1.6 | 30 ±1.5 |
Melting temperature of gelatine, °C | 27 ±1.3 | 30 ±1.5 | 31 ±1.5 |
Active acidity, pH | 5.5 ±0.2 | 6 ±0.3 | 6 ±0.3 |
Note: (n = 5,
However, first of all, dissolution is associated with the hydration of proteins, that is, the binding of water molecules to proteins. Scientists associate this phenomenon with the structural features of collagen in various fish species (
When swelling, water molecules penetrate the protein and bind to its polar groups. A dense network of polypeptide chains is delimited. Further absorption of water leads to the separation of protein molecules from the total mass and dissolution. This is the process of electrostatic binding of water molecules to the polar groups of side radicals of acidic amino acids with a negative charge and basic amino acids with a positive charge. However, swelling does not always lead to rapid dissolution, for example, animal collagen, unlike fish collagen, can remain in a swollen form, having absorbed a large amount of water. Similar statements were highlighted in the works of scientists (
The transparency of the structuring agent solution characterizes the degree of their contamination with mechanical impurities. It was found that the value of the transparency index of new structuring agents is higher than that of control. During storage, the transparency of all samples ranged from 27 – 30%. Accordingly, high transparency indicates their high quality. The predecessors (
Dynamic viscosity is one of the main characteristics of structuring agents. According to this indicator, all product samples are within acceptable limits (16 – 18 mPa.s-1). Scientists noted the higher values of viscosity indicators of fish structuring agents (by more than 18%), compared with animal gelatin (
In works (
An indicator of the quality of the structuring agents is the strength of the gelatin, which directly depends on the pH of the medium. The greatest strength is observed in the range from 5 to 7 pH.
The nutritional value of the structuring agents was examined by their chemical composition, namely, the content of proteins, fats, and minerals (Table
Chemical composition of structuring agents.
Content, % | Control (gelatine) | Structuring agents based on | ||
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secondary fish raw materials | secondary fish raw materials and cystoseira | |||
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Moisture | 14.0 ±0.7 | 15.0 ±0.7 | 15.0 ±0.7 | |
Protein | 83.0 ±4.1 | 82.0 ±4.1 | 82.0 ±4.1 | |
Fat | 1.5 ±0.07 | 1.4 ±0.07 | 1.1 ±0.05 | |
Minerals | 1.4 ±0.07 | 1.3 ±0.06 | 1.6 ±0.09 |
Note: (n = 5,
So, the high content of proteins (82%) and minerals characterizes the degree of the biological value of natural structuring agents. It should be noted that the structuring agents based on secondary fish raw materials and cystoseira contain a greater amount of minerals (1.6%) compared to the structuring agents without cystoseira (1.3%). Accordingly, the addition of cystoseira made it possible to rationalize the mineral composition of the product, since cystoseira contains a complete complex of mineral elements.
In the works (
One of the important quality criteria for structuring agents is their biological value, which is largely determined by the content and balance of amino acids, especially essential ones (
Analysis of the amino acid composition of protein structuring agents.
During studies of the amino acid composition of proteins, the structuring agents, the highest content of such amino acids was noted: glycine, alanine, proline, aspartic and glutamic acids. These amino acids form a repetitive sequence in the polypeptide chain, resulting in the helical structure of collagen. Accordingly, the high content of glycine 162.7 – 176.4 mg.100g-1 and glutamic acid 142.1 – 153.1 mg.100g-1 in research structuring agents is a characteristic feature of the amino acid composition of fish collagen. Amino acids such as histidine, isoleucine, valine are found in a smaller amount, which is due to the smaller number of cross-links. Experimental studies of the amino acid composition of fish gelatin (
It was also found that fish gelatin has a lower content of hydroxyproline, but almost 2.5 times more proline (
Amino acid rate of protein of structuring agents.
Amino acid, % | Amino acid content according to the FAO/WHO scale | Control | Structuring agents based on | |
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secondary fish raw materials | secondary fish raw materials and cystoseira | |||
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Valine | 50 | 45 | 47 | 49 |
Isoleucine | 40 | 29 | 32 | 34 |
Leucine | 70 | 50 | 71 | 74 |
Lysine | 55 | 72 | 101 | 105 |
Methionine + Cystine | 35 | 34 | 78 | 83 |
Threonine | 40 | 50 | 93 | 87 |
Phenylalanine + Tyrosine | 60 | 38 | 70 | 71 |
To assess the degree of protein utilization, the coefficient of difference of the amino acid rate was calculated. KRAS of the control sample is 16.4%, of the research ones is 37.8 – 38.2%.
The biological value of the reference protein is 100%. In experimental samples, biological value is 61.8% (structuring agents based on secondary fish raw materials) and 62.2% (structuring agents based on secondary fish raw materials and cystoseira), control ones – 83.6%. The value of the utilitarian coefficient of the amino acid composition of the experimental samples (0.618 – 0.836) indicates a high balance of amino acids relative to the standard.
Thus, the qualitative composition of structuring agent proteins based on secondary fish raw materials from silver carp indicates the expediency of their effective use in the food industry.
One of the important indicators of the nutritional value of structuring agents is the content of the main macro- and microelements in their composition (Table
Mineral composition of structuring agents, mg.100g-1.
Mineral element | Control | Structuring agents based on | |
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secondary fish raw materials | secondary fish raw materials and cystoseira | ||
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Potassium | 7.94 ±0.31 | 98.0 ±4.1 | 90.45 ±4.2 |
Calcium | 343.0 ±10.61 | 68.1 ±3.32 | 69.3 ±3.46 |
Iron | 0.91 ±0.04 | 1.09 ±0.05 | 1.02 ±0.05 |
Chlorine | 454.0 ±22.49 | 545.7 ±27.16 | 475.6 ±23.70 |
Selenium | - | - | 6.24 ± 0.28 |
Bromine | 2.78 ±0.13 | 3.37 ±0.16 | 5.01 ±0.24 |
Phosphorus | 300 ±10.12 | 120 ±5.6 | 170 ±8.1 |
Zirconium | 0.10 ±0.004 | 0.05 ±0.002 | 0.16 ±0.008 |
Sulfur | 2.1 ±0.10 | 2.8 ±0.14 | 4.98 ±0.24 |
Note: (n = 5,
Analyzing the quantitative composition of macro- and microelements of research structuring agents in comparison with the control, an increase in the level of potassium, iron, sulfur, bromine, chlorine should be noted. Experimental samples of structuring agents, in comparison with the control, contain a significant amount of potassium necessary for the human body, which ensures the normal activity of the cardiovascular system. The potassium content in structuring agents based on secondary fish raw materials is 98.0 mg.100g-1, in the sample from cystoseira – 90.45 mg.100g-1, which exceeds the value of the control sample by 113.94%.
An increased amount of iron 1.2 times in experimental samples compared to the control will contribute to a positive effect on the protective functions of the body, since iron is involved in respiration, hematopoiesis, immunobiological and redox reactions, and a sufficient amount of calcium (68.1 – 69.3 mg.100g-1) will improve its assimilation by the human body.
In terms of sulfur content, the dominant is structuring agents sample based on secondary fish raw materials and cystoseira – 4.98 mg.100g-1, because sulfur is used in the human body to neutralize many toxic products formed during metabolism.
A distinctive feature of the studied samples of the structuring agents with cystoseira is a significant bromine content, which is 5.01 mg.100g-1 which is almost twice as much as in the control – 2.78 mg.100g-1, and selenium – 6.24 mg.100g-1. The enrichment of the mineral composition of the structuring agents with bromine and selenium can be explained by their sufficient content in cystoseira.
The results of the study show that the addition of seaweed – cystoseira to the structuring agents contributes to the optimization and enrichment of their mineral composition in comparison with the structuring agents without cystoseira and the control sample.
It was found that structuring agents based on secondary fish raw materials are characterized by a high protein content (82%), which has a positive effect on the jelly-making properties of the structuring agents. The dominant amino acids are glycine, proline, alanine, aspartic and glutamic acids. The value of the utilitarian coefficient of the amino acid composition of the new structure-formers is within the range (0.61 – 0.83), which indicates a high degree of assimilation of their proteins by the human body.
It has been proven that the addition of cystoseira to the structuring agents based on secondary fish raw materials increases the content of Bromine (5.01 mg.100g-1) compared to the control (2.78 mg.100g-1) and Selenium (6.24 mg.100g-1).
Confirmed a high degree of jelly-making properties of structuring agents, characterized by a complex of indicators of viscosity (16 – 18 mPa.s-1), strength (10 – 11 H), melting point (27 – 31 °C), and solubility (5 – 6 minutes).
It was found that the addition of cystoseira to the structure-forming agents promotes optimization and enrichment of their mineral composition in comparison with the structure-forming agents without cystoseira and the control sample.
We express our gratitude to Professor Olena Sydorenko.
This study did not receive external funding.
The authors have no conflicts of interest.
This article does not contain any research that would require ethical statements.