Functional and bioactive properties of collagen and gelatin from alternative sources: A review

The growing interest in valorizing industrial by-products has led researchers to focus on exploring different sources and optimizing collagen extraction conditions over the past decade. While bovine hide, cattle bones, pork, and pig skins remain the most abundant collagen sources, there is a growing trend in the industrial utilization of collagen from non-mammalian species. This review explores alternative marine collagen sources and summarizes emerging trends in collagen recovery from marine sources, with a particular focus on environmentally friendly methods. Additionally, this review covers the colloidal structure-forming properties of marine collagens, including foam, film, gel, and emulsion formation. It also highlights the potential and important applications of marine collagen in various food products. Based on the currently reported marine sources, collagens extracted from fish, jellyfish, and sea cucumbers were found to have the highest yield and mostly comprised type-I collagen, while crustaceans and mollusks yielded lower percentages of collagen. Traditional extraction techniques isolate collagen based on acetic acid and pepsin treatment, but they come with drawbacks such as being time-consuming, causing sample destruction, and using solvents. Conversely, marine collagen extracted using conventional methods assisted with ultrasonication resulted in higher yields and strengthened the triple-stranded helical structures. Recently, an increasing number of new applications have been found in the food industry for marine collagens, such as biodegradable film-forming materials, colloid stabilizers, foaming agents, and micro-encapsulating agents. Furthermore, collagen is a modern foodstuff and is extensively used in the beverage, dairy, and meat industries to increase the stability, consistency, and elasticity of products.Graphical abstract

Extraction and characterization of gelatin from camel skin (potential halal gelatin) and production of gelatin nanoparticles

Gelatin is a water-soluble protein prepared from the extraction of collagen which is present in various animal by-products. Though the most abundant sources of gelatin are pig skin, bovine hide, and pork and cattle bones, the market data show the increased preference and demand for fish gelatin due to socioreligious reasons. The vast diversity of available fish species has necessitated the need to develop and optimize extraction procedures to recover gelatin with desirable functional properties. During the last two decades, several researchers have explored various approaches to extract fish gelatin with improved functionality. The recovery of fish gelatin mainly encompasses the pretreatment of raw materials and extraction conditions. The extraction processes have been reported to influence the amino acid composition and molecular weight distribution of polypeptide chains and, consequently, the functional properties of the gelatin. The essentials of different extraction procedures from fish waste developed by various researchers, including optimization of the extraction process by response surface methodology and the influence of extraction parameters on the functional properties of extracted gelatin, are detailed in this chapter.

An overview of gelatin derived from aquatic animals: Properties and modification

Gelatins are formed during technological stages of processing animal connective tissue proteins (primarily – collagens) and, from a biochemical point of view, are represented as various polypeptide products. In most cases, gelatins as commercial products are 52.5% made from the skin and bones of cattle; 46.0% – from pig skin and only 1.5% – using other animals. At the beginning of the 21st century, the bulk of gelatins produced are used in food products, about a third in the medical sector, and only about 6% in technical or other industrial applications. Currently, trends towards a healthy lifestyle have intensified, which, along with the religious and cultural traditions of many countries, encourages scientists to look for sources of gelatins that are not related to mammals, but are close to them in physicochemical and functional characteristics. Therefore, recently there has been a tendency that the gigantic volume of production of gelatins from mammals (cattle and pigs) is beginning to decline, although not significantly so far, compared with the relative increase in the production of gelatins from by-products and waste from industrial poultry farming. Moreover, over the past decades, global poultry meat production has increased by more than a third. The optimal content of amino acids (AA) and their ratios in gelatins from cattle and pig skin for their further use is shown. Of course, the AA content in gelatins from pig and cattle skin obtained under different technological conditions may differ significantly. However, in general, these differences are not critical and therefore, sometimes gelatins are obtained from a mixture of animal waste. Recently, in Russia, a composition of protein ingredients from hydrolysates of pig and cattle skin with the addition of dried blood plasma was proposed, which had a significantly better AA composition than in traditional gelatins, which allowed the authors to assume increased biological and nutritional value of the developed product. In addition, a number of authors have discovered an improvement in a number of indicators and biological properties of gelatins from a mixture of animal waste with the formation of a number of specific peptides. Thus, new compositions based on known gelatins with an optimal AA composition are currently being actively developed, leading to improved nutritional and functional properties. The fundamental and applied significance of this review lies in a detailed description of the main studies on the amino acid composition of gelatins and identifying their relationship with the key biochemical and technological indicators of gelatin-based materials.

SummaryThis work was initiated to optimise the factors affecting the enzymatic extraction of edible gelatin from the cattle bones using response surface methodology. A central composite rotatable design was used to evaluate the effects of the enzyme concentration, time of enzymatic treatment and extraction temperature on the yield of extraction, gel strength, apparent viscosity and absorption at 420 nm. The R2 values of regression models for all the response variables were higher than 0.9. Data analysis showed that all the process variables significantly (P < 0.01) affected the gel strength and apparent viscosity of extracted gelatin, whereas the effect of extraction temperature on both yield of extraction and absorption at 420 nm was not significant (P > 0.05). Graphical optimum conditions for the extraction yield, gel strength, apparent viscosity and absorption at 420 nm were determined as 6.1 ppm, 15.6 h, 70 °C; 9.1 ppm, 11.9 h, 70.3 °C; 7.86 ppm, 14.9 h, 77.5 °C and 2.8 ppm, 10 h, 60 °C, respectively. For all the response variables, the experimental values were very close to the predicted values and were not statistically different (P < 0.05).

Actinidin was used to pretreat the bovine hide and ultrasonic wave (53 kHz and 500 W) was used for the time durations of 2, 4 and 6 h at 60 °C to extract gelatin samples (UA2, UA4 and UA6, respectively). Control (UAC) gelatin was extracted using ultrasound for 6 h at 60 °C without enzyme pretreatment. There was significant (p < 0.05) increase in gelatin yield as the time duration of ultrasound treatment increased with UA6 giving the highest yield of 19.65%. Gel strength and viscosity of UAC and UA6 extracted gelatin samples were 627.53 and 502.16 g and 16.33 and 15.60 mPa.s, respectively. Longer duration of ultrasound treatment increased amino acids content of the extracted gelatin and UAC exhibited the highest content of amino acids. Progressive degradation of polypeptide chains was observed in the protein pattern of the extracted gelatin as the time duration of ultrasound extraction increased. Fourier transform infrared (FTIR) spectroscopy depicted loss of molecular order and degradation in UA6. Scanning electron microscopy (SEM) revealed protein aggregation and network formation in the gelatin samples with increasing time of ultrasound treatment. The study indicated that ultrasound assisted gelatin extraction using actinidin exhibited high yield with good quality gelatin.

Objective: This study aimed to isolate gelatin, determine its characteristics, and obtain analytical methods optimum for the determination of glycine,proline, and hydroxyproline levels in bovine gelatin.Methods: Bovine hide was hydrolyzed using 2% sodium hydroxide at an extraction temperature of 70°C for 3 h and a drying temperature of 60°C.Then, the gelatin extracts were evaluated using an organoleptic test; Fourier transform infrared analysis; pH measurement; and ash content, moisturecontent, and viscosity tests. Optimum analysis conditions for the determination of glycine, proline, and hydroxyproline levels in bovine gelatin usinghigh-performance liquid chromatography with a fluorescence detector were as follows: Excitation wavelength, 265 nm; emission wavelength, 320 nm;mobile phase composition of acetic buffer: acetonitrile, 55:45; flow rate, 0.8 mL/min; C18 column with length 250 mm and inner diameter 4.6 mm;and particle size, 5 μm. Derivatization of amino acids was performed using the reagent 9-fluorenylmethoxycarbonyl chloride.Results: The results showed average levels of glycine, proline, and hydroxyproline in bovine gelatin, i.e., 25.10±0.09%, 14.28±0.11%, and 13.0±0.05%,respectively.Conclusion: The optimum conditions for bovine gelatin hydrolysis included HCl with heating for 22 h at 110°C. The hydroxyproline, glycine, andproline levels obtained for analysis in bovine gelatin samples were 13.50±0.05%, 25.11±0.09%, and 14.28±0.11%, respectively.

Animal by-products (ABPs), comprising both edible and inedible components, offer significant nutritional, economic, and environmental value. However, their utilization differs markedly across global jurisdictions due to cultural preferences, regulatory frameworks, and technological capacities, which collectively shape consumption patterns and determine integration into food systems or diversion to industrial applications. While consumer reliance on offal remains high in the Global South, driven by tradition, affordability, and nutritional needs, its acceptance in the Global North is markedly lower, often limited by cultural aversion and perceived risks. Drawing from published evidence and primary survey data, this review examines regional consumption trends, industrial utilization pathways, and emerging valorization opportunities for ABPs. Globally, industrial use of ABPs is increasingly shifting toward advanced bioprocessing, integration within circular bioeconomy models, and high-value applications in nutraceutical, pharmaceutical, and bio-industrial sectors. An online cross-sectional survey (n = 358) conducted across Africa, North America, Europe, and Asia revealed strong regional disparities in offal consumption, with higher acceptance in parts of Africa and Asia and more selective use in Europe and North America. Respondents also indicated clear support for non-food valorization pathways, particularly animal feed, fertilizer, and energy production, alongside pharmaceutical and cosmetic applications. These findings align with the literature, where industrial valorization pathways such as collagen and gelatin extraction, rendering, and bioenergy production dominate. This review synthesized the jurisdictional disparities in consumption, regulation, technological capability, and industrial applications while highlighting emerging technological opportunities for high-value valorization. Recommendations emphasize consumer education, regulatory refinement, technological innovation, and sustainable practices to enhance the economic and environmental benefits of ABP utilization within a circular bioeconomy framework.

Characterization of codfish gelatin: A comparative study of fresh and salted skins and different extraction methods

There is a major focus on natural biopolymers of bacterial, animal, or plant origin as ecological materials, replacing petrochemical products. Biologically derived polylactide (PLA), polyhydroxybutyrate (PHB), and polyhydroxyalkanoates (PHA) possess interesting properties, but they are currently too expensive for most applications. Therefore, researchers try to find other biopolymers that are both durable and cheap enough to replace plastics in some applications. One possible candidate is gelatin, which can be transformed into a thin, translucent film that is flexible and has stable and high mechanical properties. Here, we present a method of synthesizing a composite material from gelatin. For preparation of such material, we used gelatin of animal origin (pig skin) with the addition of casein, food gelatin, glycerin, and enzymes as biocatalysts of chemical modification and further extraction of gelatin from collagen. Compositions forming films with homogeneous shapes and good mechanical properties were selected (Tensile strength reaches 3.11 MPa, while the highest value of elongation at break is 97.96%). After administering the samples to microbial scaring, the composites completely decomposed under the action of microorganisms within 30 days, which proves their biodegradation.

In recent decades, food waste management has become a key priority of industrial and food companies, state authorities and consumers as well. The paper describes the biotechnological processing of mechanically deboned chicken meat (MDCM) by-product, rich in collagen, into gelatins. A factorial design at two levels was used to study three selected process conditions (enzyme conditioning time, gelatin extraction temperature and gelatin extraction time). The efficiency of the technological process of valorization of MDCM by-product into gelatins was evaluated by % conversion of the by-product into gelatins and some qualitative parameters of gelatins (gel strength, viscosity and ash content). Under optimal processing conditions (48–72 h of enzyme conditioning time, 73–78 °C gelatin extraction temperature and 100–150 min gelatin extraction time), MDCM by-product can be processed with 30–32% efficiency into gelatins with a gel strength of 140 Bloom, a viscosity of 2.5 mPa.s and an ash content of 5.0% (which can be reduced by deionization using ion-exchange resins). MDCM is a promising food by-product for valorization into gelatins, which have potential applications in food-, pharmaceutical- and cosmetic fields. The presented technology contributes not only to food sustainability but also to the model of a circular economy.

Gelatin is extracted from beef or pork. One of the potential sources of gelatin to be developed apart from land base mammalian is from poultry, namely duck bones. Gelatin extraction from duck bones can be carried out by the acid method. Several studies have reported that hydrolysis of gelatin using various types of enzymes will increase its bioactivity, such as antioxidants, antibacterials, and antihyperglycemic (alpha amylase inhibitors). The purpose of this study was to determine the characteristics of duck bone gelatin which hydrolyzed with trypsin enzyme as an alpha amylase inhibitor. This study used nonfactorial completely randomized design (CRD) with different hydrolysis time treatments. Research parameters such as total soluble protein, TCA soluble protein, hydrolysis degree, and alpha amylase inhibitory activity. The results showed that the different treatment times for hydrolysis had a significant effect (P &lt;0.05) on the TCA soluble protein value and the degree of hydrolysis. However, there was no significant effect (P&gt; 0.05) on the total dissolved protein. 180 minutes hydrolysis treatment time with a concentration series of 250; 500; 1000; 2000 ppm has inhibitory activity against alpha amylase, respectively, 39.42; 41.75; 44.58; 48.11%. It has IC50 value of 2.74 mg / mL. The inhibitory activity was still weaker than the positive control for acarbose.

Conventional gelatin extraction from high‐collagen tissues requires prolonged thermal processing (8–10 h), resulting in high energy consumption and potential degradation of functional properties. To address this limitation, this study investigated ohmic heating (OH) as an alternative extraction method for bovine hide gelatin. Gelatin was extracted using voltage gradients of 5–20 V/cm for 1–5 h and compared with both conventional extraction parameters and commercial halal gelatins. OH markedly reduced the extraction time to 1–5 h while maintaining a maximum temperature of 70°C, resulting in significantly improved extraction efficiency and higher dry matter and protein contents ( p &lt; 0.05). Although gel strength (122.12–176.81 g) was lower than that of commercial bovine gelatin (242.44 g), all OH‐treated samples except those extracted at 20 V/cm formed stable gels. SDS‐PAGE and compositional analyses indicated that OH induced partial degradation of high‐molecular‐weight fractions, consistent with the observed gel strength trends. The amino acid profiles, dominated by glycine, proline, and hydroxyproline, and the viscoelastic behavior ( G ′ &gt; G ″) were comparable to commercial references. Thermal analyses further revealed sharper melting transitions and higher Δ H values, suggesting improved thermal stability. Microstructural changes in pore size and distribution supported the observed functional differences. Overall, OH‐assisted extraction provides an efficient, energy‐saving, and thermally controlled approach to gelatin production. To our knowledge, this is the first study to demonstrate the applicability of ohmic heating for extracting gelatin from bovine hide, underscoring its potential as a sustainable alternative to conventional processing methods.

Effect of acid pretreatments with various acid types on gelling properties and identification characteristics of pigskin gelatin.