2024 年 12 巻 p. 327-346
High-value product collagen derived from animal by-products has potential use in food ingredients. The utilization of collagen derived from animal by-products resources shows promise due to several characteristics is high availability. Its characteristics will be directly influenced by the type of collagen extracted. Given that its characteristics are similar to collagen from fish, this work aims to provide an overview of the collagen sources from animal by-products (skin, bone, eggshell membrane), extraction methods (acid, enzymatic, salt), properties characteristics (amino acids, viscosity, thermal stability, spectroscopy I.R, solubility, molecular weight) and potential applications for food ingredients with an emphasis on animal by-products through a compilation of scientific information that can be helpful to guide professionals in mammal biotechnology.
In the dynamic environment of the food industry and the increased awareness of health considerations, the focal point shifted towards research on food ingredients. Collagen, a protein renowned for its versatile structure, holds significant potential applications in the food sector [1, 2]. Serving as a distinctive protein type, collagen sets itself apart through its fibrous structural characteristics, integral components of the extracellular matrix in organisms [3]. Although traditionally sourced from mammals, this source showed promise in evolving into a functional food resource capable of providing health benefits and enhancing the overall quality of food products [4]. Collagen is a protein structure multifunctional for applications in the food industry. Collagen as a protein has characteristics of fiber structures which is a crucial component of the extracellular matrix in the organism. Collagen in animals is about 30% of the total protein content and can be found in the skin and bone of animal parts [5, 6]. Collagen molecule protein is unique because it has the Gly-X-Y-sequence of the triple helix in a polypeptide amino acid chain [7, 8]. The molecular structure of collagen has been identified in at least 29 collagen types.
The sustainability and efficiency linked to the extraction of collagen from sources other than mammals presented an appealing substitute, alleviating the strain on mammalian populations and introducing more sustainable choices in the domain of food [9]. Therefore, a thorough understanding of the characteristics of collagen derived from this source laid the foundation for innovative product development aligned with consumer preferences for delicious and health-promoting foods [10]. The main objective of this scientific review was to extensively explore the potential of collagen from animal by-products as a functional food ingredient. By elucidating extraction methods, enhancing the understanding of structural features, and presenting health benefits, the goal was to identify potential applications of collagen in formulating functional foods. This research not only contributes to product development but also has a beneficial effect on environmental sustainability and consumer welfare.
Initiating with an exploration of collagen, including its origins, animal by-products, and the extraction process, this review proceeded to delve into the structural features and nutritional composition of the collagen. Subsequently, potential applications in various functional food products were explored, alongside an investigation into the health benefits associated with consuming collagen from animal by-products. Through this comprehensive review, it was expected that a deeper understanding of the potential of collagen from animal by-products as an innovative and sustainable food ingredient would be achieved.
Collagen is the main protein component that is abundant in the body because one-third of the body’s protein is collagen. collagen is often found in the skin, spinal cords, skin tissue, tendons or muscles, hides, ossein, and also throughout all membranes of bones. Collagen protein is a fibrous protein that has a strong influence on the physical properties and strength of the skin with the structure of its molecules consisting of polypeptides that form a spiral or helix. Collagens consist of three polypeptide chains which are conformations triple helix and will be stabilized by intra and intermolecular hydrogen bonds as livestock age increases. Collagen contains specific amino acids such as glycine, proline, hydroxyproline, and arginine. Collagen is relatively resistant to enzymes proteolytic including trypsin and chymotrypsin but is easily attacked by the enzyme collagenase produced by Clostridium histolyticum. Collagen an insoluble fiber network can be formed which has tensile strength and has three polypeptide chains. The collagen structure is strong but flexible which makes collagen widely used for various needs collagen that has not been denatured can be used for cosmetics, and health, and applied to the pharmaceutical industry, because it is usually an industry that still requires collagen with long and strong polypeptides. Meanwhile, collagen that has been partially hydrolyzed is known as gelatin and can be utilized as collagen which is soluble in water and can be utilized more in the fields of food, pharmaceuticals, photography, cosmetics, and industry as packaging materials [11]. After being treated to a hydrolysis process with protease enzymes, some collagen can be utilized in the mechanism of skin lightening [12].
Collagen is the main protein component of connective tissue formed by multicellular organisms in all species [13]. Amino acids in the form of a triple helix, namely (glycine 25%), proline, and hydroxyproline (25%) are the composition of collagen. Collagen fiber bundles are approximately 10 µm in size and colorless [14]. Connective tissue in animals such as fish, cattle, pigs, and poultry contains abundant collagen in the form of fibrils of around 90% [15, 16]. Collagen is located in the extracellular tissue matrix such as bones, skin, tendons, and other connective tissues with its main function as support [17, 18]. In the process of cell growth and differentiation, collagen plays an important role because it produces collagen fibers with specific structures with their respective attachment abilities [19]. Primary and sub-molecular structures are the molecular components that form collagen [20]. Active producers of collagen are mesenchymal cells and their derivatives such as fibroblasts, odontoblasts, osteoblasts, cementoblasts, and chondroblasts [14].
Based on protein structure, amino acid sequence, and molecular properties, around 29 types of collagens have been studied by Shoulders and Raines [21]. These types can be observed based on their complex structure and diversity, connection variations, presence of additional non-helical domains, assembly, and function. The structure of the spine is composed of collagen types I and V. Types II, VI, VII, XI, XII, XIII, XIV, XIV, XIX, XXV, and XXVIII contribute greatly to the articular cartilage matrix and developing tissue [17]. Type IV collagen contains many flexible triple helix networks arranged only on the basement membrane. In type VI, it can be seen that the microfibrils are cross-linked with disulfides and affect the structure of the filaments between one collagen fibril and another [22]. The types with a single large molecule with the function of regulating the diameter of collagen fibrils are types IX, XII, and XIV [23]. Glucosaminoglycan chains often called proteoglycans are collagen types IX, XII, XIV, XV, XVIII [17]. Type I is a type of collagen that is widely used in the industrial sector, which is why it is also called commercial collagen. Industrial sectors that use it include food, cosmetics, biomedical, pharmaceutical, and functional food because of its various benefits such as biodegradable, biocompatible, and low antigenic capabilities. The source for type I collagen production usually comes from animals such as cows, pigs, and chickens [24]. The main factors influencing the properties and function of collagen are its type and source. The type and source of collagen determine the molecular weight of the peptide chain, solubility, and functional activity [25].
As one of the most abundant proteins in the world, collagen can be extracted from a variety of sources. Collagen is one of the most abundant proteins, it can be extracted from various sources. Nearly all living animals can produce it for extraction. However, rat tails, pig skin, and bovine skin and tendons are common sources of collagen for tissue engineering applications compared to other sources [26]. Because it functions as connective tissue in biological structures, this molecule is one of the most abundant in many living creatures. The cosmetics industry has shown great interest in collagen due to its availability, strength, and association with skin aging [27].
Bhadra et al. [28], state that investigating collagen platforms would have wide-ranging advantages for a wide variety of users, including customers, researchers, and industrialists, in the future. Since the characteristics of collagen vary from one animal to another, research into these sources is necessary. Researchers have been interested in diverse species and maximizing collagen and gelatin extraction conditions for the past ten years due in large part to the growing interest in the valorization of industrial by-products [8]. Collagen has two sources: natural sources and synthetic sources. Natural sources of collagen are generally from animals and the most popular include bovine, porcine, and human collagen, as well as marine organisms such as fish, and starfish. Synthetic Sources of collagen are frequently employed to support tissue remodeling, healing, and blood clotting. Although there are numerous clinical applications for animal-derived (natural) collagen, there are also worries about its potential to cause inflammation, batch-to-batch variability, and disease transmission. Various synthetic sources can help prevent immunological issues [27].
Collagen can also be obtained from marine organisms; sponges, fish, and jellyfish are good sources, but livestock wastes and byproducts also have the potential to be collagen sources and preserve the environment from pollution livestock wastes as well as byproducts. In livestock, several body parts contain collagen. The arteries (10–25%), cartilage (50–70%), skin (50–70%), bones (80–90%), lungs (10%), liver (4%), and muscles (80–90%) are among these body parts [29]. The most popular source of collagen comes from livestock, Among them are chicken, cow, pig, duck, and rabbit. Collagen extract from chicken bones, stirring for 6 hours resulted in a smaller particle size (1.34 μm) than stirring for 8 hours (1.80 μm on collagen extract from chicken bones. In collagen with a size of 1.34 μm, the greatest antioxidant activity was found at 24.70%, and tyrosinase inhibitory activity at 26.77% [30]. A yield of 30.049% was obtained from egg membranes during the extraction process of pepsin soluble collagen (PSC) utilizing response surface methodology (RSM) [31]. Eighty percent of the total protein found in cow tendons is found in type I collagen. Through FTIR testing, the characteristic of bovine tendon collagen obtained is its peak of 1632 cm–1 representing beta-sheet and helix structure. At the peak of 1450 cm–1 to 1235 cm–1, it is part of the triple helix structure [32].
Collagen types I and II are produced through duck foot extraction. Duck feet are extracted, including the joints, bones, and skin, The triple helix structure of collagen is formed by tiny polypeptide units called α1 and α2 chains, which are measured by electrophoresis testing [33]. Type I collagen protein is the feature of the collagen extract from sheep skin, according to FTIR tests. According to SEM results the collagen extract's structure is porous and foamy, meaning that it can be suggested as an alternative to pig collagen [34]. The size of the peptide is the main factor influencing its bioavailability in bioactive compounds. The production of short-chain peptides (<2000 Da) and the size of peptides are both greatly decreased by the collagen extract from the second digestion stage when enzymes are used [35]. Based on electrophoresis tests, the protein's molecular mass of collagen from rabbit skin reveals two α chains and one β chain, with corresponding weights of 102, 118, and 220 kDa [36]. A lot of types I collagen can be made from beef hearts. Some health science areas utilize this natural fiber because of its physical, chemical, and biocompatibility characteristics. Its qualities make it useful in certain fields of health science. The molecular mass of collagen protein obtained was 191.72, 173.56, and 161.34 kDa. The value of 173.56 kDa reflects the β chain, while the values of 125.38 and 117.33 kDa represent the α1 and α2 chains. Bovine bone collagen was extracted with 1 M NaOH to obtain a yield of 27.50% [37].
3.1 SkinsMammals skin is mostly composed of water, protein, fat, carbohydrates, and minerals. The chemical composition of fresh skin consists of 64% water, 33% protein, 2% fat, 0.20% minerals, and 0.80% other substances. Most of the protein in the skin consists of 29% collagen which is then followed by 0.30% elastin, 2% keratin, 1% globulin and albumin, and 0.70% mucin and mucoid [38]. The chemical composition of fresh skin on one livestock with others varies depending on the type of livestock, species, age, sex, and feed. There are two types of protein in the skin, namely fibrous protein and globular. The fibrous proteins consist of elastin, keratin, and collagen and are insoluble in water and organic solvents. Collagen protein is the main structural protein skin is present in large quantities, namely around 70% of the dry weight of skin. Proteins are globular consisting of albumin, and globulin, and mucin is soluble in sodium chloride. The skin components that are thought to affect the major properties of skin are elastin, glycosaminoglycans, and collagen. collagen if it is partially hydrolyzed using an acid or base, it will gelatin is produced.
3.2 BonesBone as a fortification product has wide uses. One example is the use of bone as a potential source of new calcium supplements because of its ability to chelate calcium. Bones can usually be sourced from pork, lamb, and beef [39, 40, 41]. Bone utilization can gradually public interest in using bone-derived materials effectively for the production of collagen peptides. Hu et al. [42] reported extracted collagen from cattle bone using steam explosion with characteristics similar to collagen extracted with general methods. In general, it has 60.05% protein, molecular mass is <1000 kDa, molecule form in small size, calcium-binding ability is 44.70 µg/mg, and osteoblast proliferative activity of 126.70%.
Lamb bone proteins contain a lot of protein and <90% of the protein in them is collagen [42]. So far, the use of bones has only been limited as animal feed, even though if it is processed further it will have high biological value, especially if it is processed into collagen. collagen has properties that are good for the body because it has low immunogenicity, good biocompatibility, and biological functional properties, collagen is widely used in many industries. Akram and Zhang [43] stated that collagen from chicken pectora; cartilage is by an enzymatic hydrolysis process which is then assisted by ultrasound. Collagen has excellent rheological characteristics, thermal stability, emulsification, and foaming properties. This extraction method has also previously been used by Dong et al. [44] extracted collagen from chicken bones, and [45] collagen extracted from the back skin of clown feathers (Chitala ornate) as well as collagen from chickens lung. Hu et al. (42) stated that collagen extraction from sheep bone with ultrasound has good process efficiency and can decrease protein structure of amounts of α-helix, β-sheets, and random coils.
3.3 Eggshell membranesThe chicken eggshell consists of shell membranes (inner and outer membranes) and a calcified shell. The function of the membrane in an eggshell is to retain albumen and prevent bacterial penetration [46]. The eggshell and shell membranes contain organic material such as proteins. The thickness of eggshell membranes is approximately 100 mm with a protein content of 100 g/kg of total protein [47]. The total protein of eggshell membranes contains 10% collagen [48, 49]. The eggshell membranes contain 1.70% CI, 1.80% K, 14.30% Ca, 0.44% P, and 0.15% Mg macrominerals. Besides it contains micromineral 3.40 ppm I and 1.40 ppm Mo [49]. Several experiments [46, 48, 50] reported that chicken eggshell membranes contain all amino acids and also collagens types I, V, and X. The eggshell membranes have amino acid higher hydroxyproline of about 1.5% if compared to eggshell is only 0.3%. It can be used as a natural source of bioactive compounds including glucosamine [51], hyaluronic acid [52], chondroitin sulfate [53], sulfur-rich proteins [54], uronic acid and sialic acid [46]. Some of the benefits of eggshell membranes such as treatment of osteoporosis, cosmetic materials, wound healing, flavoring, and inflammation of teeth [55].
The eggshell membranes are part of the egg containing essential nutrients in amounts high [56]. Collagen-like proteins are structural proteins mainly based on shell membranes hydroxylysine, desmosine, and isodesmosine [48]. Collagen in eggshell membranes is a source of valuable biological value. The eggshell membrane has specific physical, chemical, and thermal properties and can be applied to wider fields [57]. In the study by Mohammadi et al. [31], the yield of collagen from chicken eggshell membranes commercially was around 30.05% with treatment soaking in NaOH 0.76 mol/L for 18 h and extraction time is 43.42 h with pepsin 50 U/mg. The high-yield collagen from eggshell membranes can be used as another alternative raw material in collagen production which is eco-friendly.
The distinct structural attributes of collagen, playing a crucial role in the extracellular matrix, suggested varied applications across the food industry [58]. Collagen can be extracted from eggshell membranes as other sources besides mammalian. The eggshell membrane emerged as an intriguing area of research as an alternative reservoir of collagen [59]. The eggshell membranes have a thick shell is 100 mm with a protein content of 800–850 g/kg and most of the collagen types I, V, and X have with protein content is 100 g/kg from protein total. Eggshell membranes have 10% total protein content approximately from the total weight (60 g) of an egg [60, 61]. Extracted collagen from eggshell membranes has been analyzed for cytotoxicity, genotoxicity, and biochemical, and then it shows that collagen from eggshell membranes is safe for consumption and does not potentially risk allergic reactions and autoimmune. The extraction procedure from this source underscored both sustainability and efficiency, providing an attractive resolution for fulfilling the requirements of functional foods [62]. Collagen in the eggshell membrane not only contributed to structural dimensions but also enriched the nutritional composition of food items [55]. The potential of collagen from the eggshell membrane as a functional food ingredient became apparent in its ability to enhance the texture, stability, and nutritional profile of food products [63].
Collagen extraction methods consist of two methods, pre-treatment of raw materials and collagen extractions. Raw materials before extraction have been cleaned, cutting approximately 1 cm, and pre-treatment. The goal of pre-treatment is to clean compounds other than collagen such as connective tissues, fats, pigments, blood, hairs, and non-collagen proteins, and maximize collagen production [64]. The method for pre-treatment of extraction collagen was using alkaline pre-treatment with NaOH 0.1 M to remove non-collagen protein and ethylenediaminetetraacetic acid (EDTA) to remove calcium and other inorganic compounds [7, 65, 66] (Fig.1). The methods used for collagen extraction are acid-soluble collagen (ASC), pepsin-soluble collagen (PSC), salt-soluble collagen (SSC), and ultrasound-assist collagen (UAC). All collagen extraction procedures are in condition at -4 °C to avoid the hydrolysis of collagen. The methods used in many studies for collagen extraction from animal by-products are shown in Table 1.
The method of extracting acid-soluble collagen uses readily available and affordable chemical materials. By utilizing an acid solution, collagen can be derived from animal by-products. these acids are categorized into organic, like acetic acid, citric acid, chloroacetic acid, and lactic acid, and inorganic, such as hydrochloric acid [65, 66]. Typically 0.5 M acetic acid is widely used the pH during extraction affects collagen solubility by influencing protein density and electrostatic interactions [67]. The collagen molecules in acidic conditions will be dominant, which causes an increase in the automatic breakdown of tropocollagen and will also affect collagen solubility [36, 65, 66].
Studies have extracted collagen from animal by-products such as skin [36, 64], feet [68], and trachea [69]. Using acetic acid at 4℃ for 24–48 hours yielding between 0.65–14.49%. The yield depends on acid concentration, extraction time, solution to material ratio, and raw material conditions (species, age, diet, etc) [7, 66]. The collagen extraction with long time incubation will only that amount yield less if compared to collagen extraction with short time incubation [65]. The acid-soluble collagen has the disadvantage of low solubility level so the collagen extracted must use a low acid solution with low concentration, for example of low acid that is good to use as a solution is acetic acid which can be easy in the extraction process because it has a carboxyl group (-COOH) that can bond with the amine group (-NH2) of collagen protein.
4.2 Enzymatic soluble collagenThe safe of collagen extraction is to use enzymes that function to break down proteins. The protease enzyme is an enzyme that functions to break down proteins by hydrolyzing the peptide bond that links with amino acids in a polypeptide chain. The first is damaging the amino acids at the end of the chain and the second is destroying the peptide bonds in the protein. The extraction process using enzymes can produce higher yields compared to acid solutions, the extraction process can be fast because enzymes can reduce activity energy by catalyzing it.
Traditionally, collagen extraction usually uses acid solutions without the addition of enzymes, but in several types of species, for example, animal by-products not all collagen molecules can be dissolved just by using acid solution. Besides extraction with acid solution has disadvantages as low yield produces. Therefore, maximizing the amount of yield produced needs adding enzymes as the solution [7, 70, 71]. Enzymes commonly used as solutions include pepsin, trypsin, papain, and collagenase [65, 66].
Pepsin is a type of enzyme that is usually used to extract collagen, so it is called pepsin soluble collagen (PSC) [65, 66]. The using of pepsin as a collagen solution must be combined with acid because pepsin activity will only be maximal if in acid condition. Pepsin activity in solution without causing damage to the integrity of the collagen triple helix when breaking down bonded telopeptides intermolecular crosslinking [72]. The various studies about collagen extraction from animal by-products using limited pepsin with acid can increase the yield of collagen can be shown in Table 1[7, 31,36, 43, 68, 69, 73, 74, 75, 76, 77]. Besides using pepsin, collagen extraction from chicken feet is also used as a papain enzyme as reported by Dhakal et al. [78]. Some of the benefits of using collagen extraction by pepsin such as:
2. Makes it easier to hydrolyze tropocollagen because its molecules easily dissolve in acidic conditions so that collagen extraction can be optimal and increase the yield.
3. Pepsin can reduce antigenicity which can affect telopeptides in the collagen molecule which is a significant problem in the food and pharmaceutical industries [71, 79, 80].
This method is usually used for collagen extraction from fish using NaCl solution. Extraction using salt solution is rarely used for collagen extraction. A previous study by Liang et al. [70] and Wang et al. [71] reported that salt-soluble collagen derived from Amur sturgeon skin and cartilage (Acipenser schrenckii) was extracted using 0.45 M NaCl in a ratio of 1:100 which was incubated for 24 h with continuous stirring.
4.4 Ultrasound-assist collagenUltrasound, an environmentally friendly technology, can enhance protein extraction by accelerating the process of extraction and enhancing the functional characteristics of the protein, thus turning it appropriate for industrial utilization [41]. High-intensity ultrasound (20 kHz) has become increasingly popular in recent years for enhancing various processes such as mixing, drying, homogenizing, dispersion, and extraction [45]. The utilization of ultrasound in collagen extraction methods has grown increasing in popularity, confirmed by several studies [41, 42, 43, 45, 69]. The ultrasound-assisted treatment and the accelerating force of ultrasonics are believed to enhance the functional qualities of protein by modifying its physicochemical characteristics [42]. Petcharat [45] reported that ultrasound can improve the efficiency of extraction by utilizing a cavitation effect. This effect occurs when the strong shear gradient resulting from the burst of microbubbles disrupts the cell wall in the skin tissue, thereby releasing collagen.
An ultrasound-assisted technique, using specific conditions (80% amplitude for 10 minutes), can be employed to enhance the extraction efficiency of collagen from clown featherback (Chitala ornata) skin, while minimizing any negative impact on the structure of molecules of the extracted collagen [45]. Utilizing high-intensity ultrasound enhances the extraction of collagen from broiler trachea and preserves the strength of the collagen structure [69]. Akram and Zhang [43] stated that the collagen obtained from chicken sternal cartilage using ultrasound treatment had an amino acid profile that was above requirements and demonstrated excellent thermal stability, making it highly suitable for industrial use. The application of ultrasound significantly enhanced the efficiency of extracting collagen from sheep bones. Furthermore, it enhanced the properties of collagen, leading to enhanced solubility, oil absorption, and stability of emulsions [42]. The collagen extraction method, such as acid-soluble, electrodialysis, pepsin-soluble, ultrasound, or isoelectric precipitation, can directly impact its properties. This might make it difficult to compare the collagen qualities obtained from various experiments [15].
| Raw materials | Method | Time (h) |
Yield (%) |
Solubility | Molecular mass (kDa) | References | |
|---|---|---|---|---|---|---|---|
| pH | NaCl (%) | ||||||
| Rabbit skin | ASC | 24 | 9 | 6.20–6.40 | - | 102–220 | [36] |
| PSC | 48 | 71 | |||||
| Tunica albuginea pig testes | PSC | 28 | 30 | [81] | |||
| Cattle tendon | UAC | 48 | 2.40 | 2–4 | 1 | 116–120 | [82] |
| UPAC | 45 | 2.70 | |||||
| Yak bovine tendons | UAC | 24 | 31.04 | [83] | |||
| “Kacang” goat skin | PSC | 24 | 93.99 | 1 | 25–180 | [74] | |
| ASC | 48 | 7.74 | [84] | ||||
| Eggshell membrane | PSC | 43.42 | 30.054 | [31] | |||
| Porcine lung | PSC | 72 | 67.02 | - | - | 100–220 | [85] |
| Chicken feet | PSC | 48 | 49.10 | 116–220 | [68] | ||
| ASC | 48 | 14.49 | |||||
| SSC | 48 | 1.13 | |||||
| Chicken trachea | PSC | 48 | 3.10 | 116–135 | [69, 78] | ||
| ASC | 48 | 0.65 | |||||
| UASC | 42 | 1.58 | |||||
| UPSC | 36 | 6.28 | |||||
| Chicken feet | Papain hydrolysis | 28 | 32.16 | 25–150 | [78] | ||
| Lamb by-product | PSC | 72 | 18 | 5 | 5–250 | [75] | |
| Sheep by-product | PSC | 72 | 12.50 | 5 | |||
| Chicken skin | PSC | 24 | 38.90 | 2.60 | [76] | ||
| Sheep bone | USC | 48 | 35 | 3–5 | 2–3 | [86] | |
| Rabbit meat | PSC | 96 | 9 | 1 | 100–250 | [77] | |
| Rabbit skin | PSC | 96 | 24.40 | 1 | |||
| Rabbit ear | PSC | 96 | 23.80 | 3 | |||
| Chicken sternal cartilage | PSC | 96 | 84.13 | 100–245 | [43] | ||
| UPSC | 36 min | 87.17 | 135–245 | ||||
The amino acid composition directly influenced the collagen’s physical-chemical properties (e.g., solubility in NaCl solution, cross-linking ability, and thermal stability). The study of the amino acid composition of collagens revealed that the molecular composition of species varies, leading to distinct structures which can be shown in Table 2. Amino acids of collagen from animal by-products are different from collagen from fish. The amino acid content in some collagen from animal by-products compared to fish skin collagen is shown in Table. Collagen from fish is high in glycine and proline, but low in hydroxyproline if compared to collagen from animal by-products. The amount and stability of hydroxyproline in mammals is higher compared to fish collagen. The amino acid content of collagen from animal by-products (cattle, sheep, and pig) has glycine and proline as well as collagen from fish. Overview, collagen has tyrosine, hydroxylysine, tyrosine, methionine, cysteine, tryptophan, and histidine in low content. Histamine is a precursor of histidine which can be used for allergic responses [81].
The amino acid that compounds the most abundant collagen is glycine [5, 82] Glycine, proline, and hydroxyproline are structured primarily of collagen characteristics with forming tripeptide units by glycine-X-proline or glycine-X-hydroxyproline, in which X is the standard 20 amino acids [83]. Glycine (36%) of collagen is more all types of other amino acids and characteristic of type I collagen [84]. Collagen is composed of basic molecules forming from three chains of polypeptides which form a triple helix structure. The amino acid glycine is 35% of the constituent amino acids triple helix of collagen is proline and hydroxyproline [85]. The function of glycine is to reduce steric hindrance and promote bonding interactions with hydrogen in the helix chain [86]. The total of amino acids collagen in each species is different. The amino acid of collagen also influences collagen characteristics because collagen is a fibrin protein fiber composed of some amino acids.
| Amino acid | Cattle tendon [82] | Kacang goat skin [64] | Chicken feet skin [78] | Sheep bone [93] | Pig skin [94] | Calfskin [82] | Fish skin [95] |
|---|---|---|---|---|---|---|---|
| Ala | 116 | 3.53 | 7.35 | 109 | 9.70 | 119 | 127.08 |
| Arg | 48 | 2.43 | 7.22 | 51 | 45.40 | 50 | 51.84 |
| Asx | 42 | 3.32 | 7.75 | 47 | 28.10 | 45 | 44.54 |
| Cys | 2 | 2.18 | - | - | 0.80 | 0 | - |
| Glx | 76 | 3.50 | 8 | 84 | 57.40 | 75 | 69.13 |
| Gly | 336 | 30.52 | 16.30 | 317 | 313 | 330 | 359.77 |
| His | 3 | 0 | 0.50 | - | - | 5 | 5.23 |
| Hyl | 8 | - | 2 | 6 | - | 7 | 5.23 |
| Hyp | 99 | - | 14.15 | 101 | - | 94 | 49.43 |
| Ile | 9 | - | 2 | 11 | 9.20 | 11 | 9.11 |
| Leu | 21 | 1.60 | 5.46 | 26 | 21.40 | 23 | 21.67 |
| Lys | 25 | 1.47 | 6.10 | 28 | 41.60 | 26 | 25.03 |
| Met | 5 | 0.31 | 1.90 | 6 | 6.10 | 6 | 9.14 |
| Phe | 2 | 0.94 | 3.30 | 13 | 14.90 | 3 | 12.18 |
| Pro | 125 | 4.55 | 8.70 | 120 | 12.90 | 121 | 135.52 |
| Ser | 37 | 1.68 | 3.25 | 30 | 29.40 | 39 | 35.33 |
| Thr | 20 | 0.45 | 2.70 | 20 | 14.70 | 18 | 24.84 |
| Trp | 0- | - | - | - | 2.10 | - | - |
| Tyr | 2 | 0.05 | 0.82 | 3 | - | 3 | 2.24 |
| Val | 22 | 1.34 | 2.50 | 23 | 21.10 | 21 | 17.93 |
| Imino acid | 224 | - | 221 | - | 215 | 184.96 |
Collagen viscosity is influenced by the proportion of β and γ chains that can influence the average molecular weight. Temperature and viscosity are related to each other because when collagen is extracted at temperatures above 30℃ the viscosity of collagen becomes very low. Viscosity is the flow force of molecules which indicates the internal viscosity solution system. Collagen viscosity begins to decrease at hydrolysis time at 30⁰C. The collagen structure becomes unstable and denatured when heating at high temperatures because it causes bonding hydrogen is broken off so that collagen viscosity becomes low [11, 82].
Billmeyer [87] reported that longer polymer compounds have a higher viscosity when compared to polymer compounds short ones of the same type. The high and low collagen viscosity values are affected by temperature, attractive forces between molecules, and the total of molecules that are dissolved. The higher viscosity of collagen at the same temperature affected the more of the total molecule is dissolved. The higher molecular weight also affects the high and low viscosity values of collagen. The high-value viscosity of collagen is related to strong electrostatic repulsion between collagen molecules in solution [88].
Viscosity is influenced by various factors, including concentration, shear rate, and temperature. It decreased as the concentration decreased. The total elimination of this phenomenon can be achieved through the augmentation of the concentration of an additional salt. The findings suggested that the atypical viscosity was a consequence of a vast, intermolecular electrostatic interaction. As the shear rate increased, there was a drop in viscosity. The shear-thinning cavitation phenomenon occurred due to the collagen molecules high aspect ratio. The temperature rise increased the viscosity of the collagen solutions, which can be attributed to the binding of collagen molecules at elevated temperatures [89].
Temperature is an important factor in the study of polymer solution viscosity. The intrinsic viscosity increased with an increase in temperature. It is caused by the collagen molecules in dilute solution tend to associate at high temperatures due to the enhancement in the hydrophobic interactions among the collagen molecules. Indeed, the collagen molecules are prone to aggregate in solution at high temperatures [90, 91].
5.3 Thermal stabilityThe thermal stability of collagen has an essential role in collagen characteristics. The fundamental principle behind collagen is the inherent stability of its triple helix structure across many physiologic conditions. Upon exposure to elevated temperatures, the hydrogen bonds inside collagen would be easily disrupted, resulting in a conformational alteration. Thermal denaturation would occur at temperatures exceeding a specific threshold. The thermal stability of collagen can be assessed by examining its shrinkage temperature (Ts) and denaturation temperature (Td). Higher values of Td or Ts are indicative of improved thermal stability [92]. In contrast to their original form, the thermally denatured forms of collagen (gelatin and collagen hydrolysate) exhibit unique properties. The characteristics encompass a somewhat reduced molecular weight, the lack of conformation translation, the diminished capacity for fibril formation, and a marginally favorable impact on the adsorption and proliferation of keratinized cells. Preventing heat denaturation is crucial during the production, storage, and application of materials. The thermal stability of collagen has been a subject of ongoing inquiry.
Various elements can impact the thermal stability of collagen. Zhang et al. [92] stated that there are 5 factors, such as collagen sources, extraction methods, solvent systems, blending with polymers, and cross-linking. Fujii et al. [93] declared that collagen thermal stability can be adjusted according to environmental temperature. Based on Zhang et al. [92], acetic acid and pepsin are the best ideal catalysts due to the high yield of extraction and Td. The difference in denaturation temperature (ΔTd) between ASC and PSC was more than 1 °C. In collagen sources, the distribution of collagen members differs significantly. Selecting a supplier that is high in the necessary collagen is crucial. The bulk of collagen sources are low-cost animal skins, such as that from pigs, cows, and sheep, as well as chickens, rabbits, and deer. Collagen taken from terrestrial animals often has better thermal stability than collagen from aquatic animals.
Differential scanning calorimetry (DSC) detection was utilized to analyze the thermal behavior of the various collagen species to further investigate the connection between amino acid concentration and thermal stability. The elevated transition temperature suggests that the collagen exhibited greater stability when exposed to elevated temperatures. The durability of collagen-based biomaterials is also influenced by thermal stability. Different species of collagen were subjected to DSC tests to investigate their thermal characteristics. Notably, collagen sourced from aquatic animals demonstrated a lower transition temperature compared to collagen sourced from mammals. Prior research has demonstrated a positive association between ambient temperature and the amino acid makeup of specific species. Aquatic collagen is generally recognized for its notably reduced denaturation temperature [94].
5.4 Spectroscopy I.RFunctional proteins were measured using an IR spectrophotometer and from the results of the measurements, a collagen spectrum will appear with 5 middle A, B, I, II, and III. Area middle A indicates the absence of NH groups and the presence of a CH group. In the middle area, I show the presence of the C=O group which is the secondary structure of proteins. The middle region II shows the presence of NH and bonds the amide III region shows the presence of an N-H bond indicating the presence of a helix structure [5]. Amide I consists of four components of protein secondary structure, namely α-helix, β-sheet, β-turn, and overlapping random coil. Kong and Yu [95] stated that the α-helix component is shown in the region absorption between 1654–1658 cm–1; β-sheet between 1624–1642 cm–1; β-turn between 1666, 1672, 1680, and 1688 cm–1; and random coil between 1648 ± 2 cm–1. The resulting collagen was not degraded to gelatin with the triple helix structure still present. The process of breaking hydrogen bonds and covalent because heating >45 °C results in disruption of the stability of the triple helix structure of collagen so that it changes shape into a coil. Finally, collagen is degraded into gelatin [8].
| Field | Source | Product | Results | Reference |
|---|---|---|---|---|
| Food Industry | collagen | Beef burger | Collagen in a burger can increase the hardness of the burger's texture. The combination of collagen and maltodextrin produced the most favorable sensory test. | [105] |
| Food Industry | Pork skin collagen | Sosis red harbin | The addition of pork skin collagen powder resulting from 20 minutes of heating at 80 °C resulted in stable texture elasticity, reduced cooking loss and yellowness. | [106] |
| Food industry | collagen | Chicken patties | A combination of 20% collagen and 10% wheat as pre-emulsion in chicken patties can reduce cooking loss, and increase panelists' satisfaction. | [107] |
| Food industry | collagen | Frankfurter sausage | The use of collagen in organoleptic sausages can improve texture and flavor, as well as increase ash and protein content. | [108] |
| Food industry | Fish collagen | Buffalo patties | Replacement of fat in buffalo patties with fish collagen, for the most part, did not show significant results on yield, cooking loss, whc, and pH. However, the use of fish collagen can increase protein and ash content, and decrease fat content. | [109] |
In general, collagen can be dissolved under acid conditions with a maximum pH for dissolving collagen from skin is 2 and for bones is 5. The pH difference occurs to dissolve from bones and skin due to molecular properties and the conformation of each collagen is different. Collagen from the skin has crosslinks less than that of collagen from bones. The total crosslinks affect the level of solubility of collagen so that collagen derived from bones has a high level of solubility which is higher than collagen from the skin [82]. Collagen solubility can also be caused by temperature. Collagen is present at room temperature and has a higher solubility than at room temperature of 4 ℃. the kinetic energy of molecules becomes higher when it is at room temperature which causes more collisions between molecules often so that the solubility of collagen at room temperature is higher [96].
The main amino acids of collagen are glycine, proline, and hydroxyproline. The extraction solution is also included to determine collagen solubility. Collagen extracted with pepsin will have a high level of solubility compared to acid solvents. Glycine is the largest amino acid of collagen. Type of amino acids tryptophan and cysteine are not found in collagen, otherwise the tyrosine and histidine content in collagen is also very low [5]. The amount and stability of hydroxyproline in mammals is higher in comparison with fish collagen. Collagen from the skin in large quantities with higher levels of hydroxyproline, proline, and arginine than derived collagen from bone but the amount of glycine and hydroxylysine in skin collagen is lower [82]. Amino acids that are more specific to collagen are hydroxyproline [97]. Amino acid residues of collagen peptides in each individual are known to be 1,050 and the chain is quite long [98].
5.6 Molecular weightSDS-Page is an analysis used to measure the of weight protein molecules. The principle of this analysis is to separate proteins based on molecular weight. This analysis uses two gels during running which consists of stacking gel and resolving gel. One of the ingredients used in this analysis is β-mercaptoethanol which functions for breaking disulfide bonds and reduces them to sulfhydryl groups, whereas SDS functions to form negatively charged protein complexes so that proteins will move in an electric field based on molecular weight [99]. Collagen has two bands (α1 and α2). Type 1 collagen is present in bones, dermis, tendons, ligaments, and cornea have a molecular composition [α1(I)2α α2(I)]. A study by Zhang et al. [88] showed that collagen derived from the skin of bluefin tuna has a molecular mass of α1 is 120 kDa, α2 is 112 kDa, and β 205 kDa, while collagen type 1 of goldfish, scales have α1 is 117.3 kDa and α2 is 107.4 kDa.
| Field | Source | Product | Results | Reference |
|---|---|---|---|---|
| Food Industry | collagen protein hydrolysate | Fermented milk | The addition of collagen to fermented milk after 21 days of storage decreased the pH and total number of lactobacillus bacteria. However, the addition of collagen can increase gel strength and reduce syneresis. | [114] |
| Food Industry | Collagen hydrolysate and bovine collagen | Sheep fermented milk | Sheep milk fermented with L. acidophilus and L. casei had good viability. The addition of collagen, either in the form of hydrolysate or bovine collagen, resulted in a darker color and increased the sweetness intensity of the fermented sheep milk. However, the addition of hydrolysate was effective in reducing syneresis in each milk sample compared to the control. | [115] |
| Food industry | Collagen | Jelly yogurt susu kambing | The 1% calcium and 2% collagen addition treatment contained higher protein, antioxidant, and sensory attribute scores than the control. The microbiological quality of the treatment was also in line with Thai product standards. (520/2547). So goat milk yogurt jelly added with 1% calcium and 2% collagen has the potential to be a good source of protein, minerals, and antioxidants. | [116] |
| Food industry | Collagen hydrolysate | Milk whey | The 1% collagen addition treatment showed the highest protein content and antioxidant activity. Viscosity increased significantly with increasing concentration of hydrolyzed collagen. The addition of hydrolyzed collagen improved the bioavailability, nutritional value, and antioxidant activity of the beverages. Hydrolyzed collagen acted as an antimicrobial agent, as no presence of pathogenic microorganisms was observed in the treated beverages. | [117] |
| Food industry | Collagen hydrolysate | Milk fermented | The addition of collagen encapsulation to yogurt sets is high in antioxidants and nutrients and provides stable rheological properties. | [118] |
There has been much research on collagen application in food products. Some of the food products that have been studied include meat, dairy, and bread-based food products. Meat-based food products with added collagen are found in sausages and patties can be show in Table 3. In patties, collagen can be added up to 20% [100]. The addition of collagen to patties will increase panelists' liking of sensory tests [100, 101] this is because adding collagen to patties will improve the texture of the product [101]. Ibrahim et al. [102] reported that the addition of collagen in patties can also increase protein content, and ash and can reduce fat. The use of collagen in sausage products is reported to produce a more elastic texture, increase protein and ash content reduce cooking loss, and give a more yellowish sausage color [103, 104]. Organoleptic test results of sausages added with collagen, panelists liked the texture and taste [104].
Dairy products in which collagen was added were processed fermented milk can be show in Table 4. The addition of collagen to fermented milk produces fermented milk that has a good texture and can reduce syneresis [105, 106, 107]. The addition of collagen in fermented milk up to 2% contains high protein and high antioxidant activity [106, 108, 109]. Where collagen has the potential to be a good source of protein and antioxidants [108]. As reported by Musika et al. [109], collagen acts as an antimicrobial agent, as no pathogenic microorganisms were observed in the treated beverages.
In the addition of collagen to bread products can be show in Table 5, it was reported that the sensory test results of panelists mostly accepted bread products added with collagen [110, 111, 112]. Bread added with collagen will give a more tender texture and bread has a better appearance, this is due to a decrease in dough volume [110, 111, 112, 113, 114]. As reported by Wang et al. [111] and Meng and Kim [112], the addition of collagen can extend the shelf life. From the above review, it can be concluded that collagen has a positive effect on the product. Collagen can improve the texture of the product, and provide higher protein, and in the sensory test, panelists liked it.
| Field | Source | Product | Results | Reference |
|---|---|---|---|---|
| Food Industry | Hydrolyzed collagen prepared from Tilapia | Bread | Hydrolyzed collagen with contents of 1%, 2%, 3%, 4%, and 5% was added to the bread. The results showed that the addition of collagen peptides improved the water retention of bread, increased the specific volume of bread, and slowed down the kneading of bread. Comprehensive comparison, the quality of bread was achieved optimally with 3% hydrolyzed collagen. In the sensory test, panelists were able to accept the collagen-treated bread. | [120] |
| Food Industry | Marine fish collagen | Fermented rice bread | The addition of marine fish collagen and marine pineapple extract can extend the shelf life and provide hardness and cohesiveness to fermented rice bread. The addition of marine fish collagen for the sensory test of texture, taste, and appearance is best. | [121] |
| Food industry | Marine fish collagen | Fermented rice bread | The addition of marine fish collagen to fermented rice bread can extend the shelf life to 0.8 days and provide better color and softness sensory values than the control. | [122] |
| Food industry | Collagen | Dough nongluten | The addition of collagen to bread can reduce the viscosity of the dough but in the sensory test, the addition of collagen to bread is less preferred when compared to the addition of pea protein. | [123] |
| Food industry | Collagen | Dough nongluten | The addition of collagen to the bread decreased the volume of the dough but gave a soft effect to the bread. | [124] |
An overview of the primary collagen characterization and application for food ingredients is given in this paper, with emphasis on sources from animal by-products. It is an overview of data from scientific publications that can help professionals working on animal by-products. This work presents an overview of the physicochemical characteristics and applications for food ingredients of animal by-product collagen, along with its implications and industrial applications in comparison to fish collagen. methods of extraction are also examined as a critical element in maintaining the properties of collagen. Given the imperative to adjust to present circumstances and mitigate environmental harm, collagen derived from animal by-product wastes emerges as a valuable resource for sustainability and impact mitigation. Given that the characteristics of collagen from animal by-products are similar to those from fish, we expect that this paper will stimulate the use of collagen from animal by-product sources in future research that will be established in the collagen global market.
This investigation was sponsored by RIIM LPDP Indonesia under contract number 27/III.11/HK/2022.
The authors declare that there is no conflict of interest.
