Fish By-Product Collagen Extraction Using Different Methods and Their Application

Molecular mechanisms and softening effects of edible acids on the intermuscular bones of grass carp (Ctenopharyngodon idella)

This study aimed to mitigate the health threats posed by intermuscular bones (IMBs) of grass carp (Ctenopharyngodon idella) by immersing them in dilute acetic acid (AA) and citric acid (CA). The hardness of AA-immersed IMBs reduced from 44.60 ± 0.25 N to 4.65 ± 0.34 N and CA-immersed IMBs from 44.27 ± 0.23 N to 3.58 ± 0.36 N. The reduction in IMBs hardness was attributed to the partial denaturation of collagen and hydroxyapatite, as shown by multispectral analysis and microstructural changes. Furthermore, sensory analysis confirmed that AA 0.75 mmol/L and CA 0.50 mmol/L significantly reduced IMBs hardness in the fish fillets (P < 0.05). Additionally, the use of these edible acids not only reduced IMBs hardness but also enhanced the textural and sensory attributes of the fish fillets, as demonstrated by textural parameters, color analysis, TVBN, and TBARS analysis. It is recommended that AA 0.75 mmol/L and CA 0.50 mmol/L can be used for IMBs softening and improving the acceptability of grass carp (C. idella) fillets in terms of texture, flavor, and aroma.

Unveiling an innovative sustainable blue resource-ecofriendly extraction technique towards a circular economy: Optimization of natural deep eutectic solvent and ultrasonication synergistic pathways for type-I collagen refined recovery from discarded fish scales

A vast sum of fish waste is being annually discarded by marine fishing industries imposing serious environmental pollution concerns. However, these aquatic discarded matters are captivating sources of collagen, a fibrous protein with eminent social and economic relevance. Collagen is conventionally recovered using outdated complex processes requiring many reagents, multiple steps, and extended periods. Hereupon, the current project is the first work on the isolation of Seabass fish scales (FSC) type-I collagen, with preserved secondary and triple helical structures of the native collagen, developing a simple, green, cost-effective, and eco-friendly methodology, utilizing sustainable natural deep eutectic solvents (NADES)-assisted ultrasonication (US) technical route. The operational conditions were optimized based on the one-factor-at-a-time modeling to maximize the yield with no alteration of collagen integrity. Recorded data confirmed type-I collagen with preserved triple helix integrity and thermal stability, improved bio-functionalities, in vitro fibril formation, and functional performances. Finally, the in vitro hemolysis and cytotoxicity tests confirmed the extracted collagens biocompatibility, demonstrating the feasibility of Seabass FSC waste and a NADES-coupled US brief process (20 min) to establish a more sustainable eco-friendly pathway to isolate high-quality type I-collagen, as an attempt to rise industries awareness about wastes valorization within the scheme of circular economy.

Unlocking the Potential of Marine Sidestreams in the Blue Economy: Lessons Learned from the EcoeFISHent Project on Fish Collagen

This review provides a general overview of collagen structure, biosynthesis, and biological properties, with a particular focus on marine collagen sources, especially fisheries discards and by-catches. Additionally, well-documented applications of collagen are presented, with special emphasis not only on its final use but also on the processes enabling sustainable and safe recovery from materials that would otherwise go to waste. Particular attention is given to the extraction process, highlighting key aspects essential for the industrialization of fish sidestreams, such as hygiene standards, adherence to good manufacturing practices, and ensuring minimal environmental impact. In this context, the EcoeFISHent projects have provided valuable insights, aiming to create replicable, systemic, and sustainable territorial clusters based on a multi-circular economy and industrial symbiosis. The main goal of this project is to increase the monetary income of certain categories, such as fishery and aquaculture activities, through the valorization of underutilized biomass.

Fabrication, modification, interaction mechanisms, and applications of fish gelatin: A comprehensive review

Fish gelatin (FG) is an essential natural biopolymer isolated from aquatic sources and has been considered as a feasible substitute for mammalian gelatins. However, its inferior mechanical and gelling properties limit its applications. Consequently, FG has been modified using various methods. This review summarizes the extraction techniques (including traditional acid and alkaline methods, as well as newer technologies such as ultrasonic-assisted and microwave-assisted extraction), modification strategies (mechanical treatments, physical mixing with polysaccharides, utilization of the Hofmeister effect, chemical modifications, etc.), along with their mechanisms of action. Additionally, we discussed the applications of FG and its modified products. Furthermore, this review highlights the safety and prospects for FG and its derivatives. The mechanical properties and biological functions of FGs are enhanced after modification. Thus, modified FG composites exhibit diverse applications in areas such as foaming agents and emulsifiers, food packaging, three-dimensional printing, drug delivery systems and tissue engineering. This paper aims to provide comprehensive information for future research on FG with the intention of broadening its applicability within the industries of food, cosmetics, and pharmaceuticals. Nevertheless, the development of tough gels, aerogels, and stimuli-responsive hydrogels based on FG requires further investigation.

Photo-Crosslinking Hydrogel Based on Porcine Small Intestinal Submucosa Decellularized Matrix/Fish Collagen/GelMA for Culturing Small Intestinal Organoids and Repairing Intestinal Defects

Organoid technology, as an innovative approach in biomedicine, exhibits promising prospects in disease modeling, pharmaceutical screening, regenerative medicine, and oncology research. However, the use of tumor-derived Matrigel as the primary method for culturing organoids has significantly impeded the clinical translation of organoid technology due to concerns about potential risks, batch-to-batch instability, and high costs. To address these challenges, this study innovatively introduced a photo-crosslinkable hydrogel made from a porcine small intestinal submucosa decellularized matrix (SIS), fish collagen (FC), and methacrylate gelatin (GelMA). The cost-effective hydrogel demonstrated excellent biocompatibility, tunable mechanical properties, rapid gelation properties, and low immunogenicity. Importantly, the proliferation and differentiation capacities of small intestinal organoids cultured in hydrogel were comparable to those in Matrigel, with no significant disparity observed. Furthermore, after one week of transplantation in nude mice, the hydrogel-organoid complex exhibited sustained structural and functional stability while preserving the differentiation characteristics of small intestinal organoids. Our study also demonstrated the effective potential of FC/SIS/GelMA hydrogel in accelerating the repair process of small intestinal defects, reducing the area of scar formation, and promoting the regeneration of both intestinal villi and smooth muscle tissue. In summary, this study presents a novel protocol for culturing small intestinal organoids, offering potential implications for future clinical applications and serving as an experimental foundation for the development of tissue-engineered intestines based on small intestinal organoids.

Monitoring fish freshness with pH-sensitive hydrogel films containing quercetin or eucalyptol

This research developed pH-sensitive smart films using carboxymethyl cellulose (CMC) and collagen (COL), combined with either quercetin (QCT) or eucalyptol (EUC), to prevent fish meat spoilage. COL, extracted from isinglass, was confirmed as type I through SDS-PAGE. The films were characterized using FESEM, FTIR, and TGA. The addition of QCT or EUC enhanced antioxidant levels to 60.16% and 70.83%, respectively, up from a baseline of 10.4%. It also increased tensile strength from 3.32 ± 0.22 to 11.8 ± 0.25 and 13.2 ± 0.27 MPa, and enhanced elongation at break from 5 ± 3.1% to 27.7 ± 1.1% and 30.15 ± 2.1%. Fish meat packaged with QCT showed a lower spoilage rate due to the antibacterial and antioxidant effects of EUC and QCT (TVBN = 7.37 ± 0.01), compared to CMC/COL film (TVBN = 10.11 ± 0.02) and non-packaged fish (TVBN = 11.23 ± 0.01). The films exhibit >80% transparency, highlighting their suitability for food packaging. CMC/COL/QCT is preferred for fish packaging because it offers better mechanical properties and lower TVB-N levels.

A Highly Specific and Versatile Biochip for Ultra-Sensitive Quantification of Denatured Collagen in Assessing Collagen Quality

Collagen, a widely used biomaterial, is susceptible to denaturation during production from native tissues, posing serious challenges for its applications in tissue engineering. Accurate quantification of denatured collagen (DC) is essential for evaluating the quality of collagen-based biomaterials, yet quantitative methods for assessing collagen denaturation are lacking. Here, we for the first time present a highly specific biochip for sensitive quantification of denatured collagen levels (Ldc), addressing this critical need in collagen quality analysis. The denatured collagen-specific chip (DCSC) features an intrinsically nontrimerizing peptide probe, F-GOP-14, targeting denatured collagen and a fully denatured collagen-coated capture surface. The DCSC demonstrates exceptional sensitivity and accuracy in quantifying DC concentration (Cdc) and total collagen concentration (Ctc), enabling precise calculation of Ldc. Importantly, DCSC is versatile, detecting Ldc across various denaturing scenarios, including UV radiation, thermal environments, and decellularization. This denatured collagen-specific biochip offers a robust method for accurately analyzing Ldc, with significant potential for enhancing collagen quality assessment in biomaterial development and production.

Comprehensive review on collagen extraction from food by-products and waste as a value-added material

The consumption of animal products has witnessed a significant increase over the years, leading to a growing need for industries to adopt strict waste control measures to mitigate environmental impacts. The disposal of animal waste in landfill can result in diverse and potentially hazardous decomposition by-products. Animal by-products, derived from meat, poultry, seafood and fish industries, offer a substantial raw material source for collagen and gelatin production due to their high protein content. Collagen, being a major protein component of animal tissues, represents an abundant resource that finds application in various chemical and material industries. The demand for collagen-based products continues to grow, yet the availability of primary material remains limited and insufficient to meet projected needs. Consequently, repurposing waste materials that contain collagen provides an opportunity to meet this need while at the same time minimizing the amount of waste that is dumped. This review examines the potential to extract value from the collagen content present in animal-derived waste and by-products. It provides a systematic evaluation of different species groups and discusses various approaches for processing and fabricating repurposed collagen. This review specifically focuses on collagen-based research, encompassing an examination of its physical and chemical properties, as well as the potential for chemical modifications. We have detailed how the research and knowledge built on collagen structure and function will drive the new initiatives that will lead to the development of new products and opportunities in the future. Additionally, it highlights emerging approaches for extracting high-quality protein from waste and discusses efforts to fabricate collagen-based materials leading to the development of new and original products within the chemical, biomedical and physical science-based industries.

Valorisation of salmon backbones: Extraction of gelatine and its applicability in biodegradable films

Salmon backbones make up about 10 % of the total fish weight and contain valuable proteins, collagen and lipids that can be used for marine ingredients production. Gelatine is derived from the collagen fraction and this study evaluated how different fractionation and extraction procedures can affect the yield and composition of extracted gelatine. Fractionation by mild thermal treatment of backbones (10 min in 40-42 °C) leads to structural changes of muscle, which improves separation of meat from bones and gives better yield of de-muscled backbone fractionation compared to mechanical meat removal. The highest yield of the gelatine (9.3 ± 0.3g dry gelatine from 100g de-muscled backbone dry material) was obtained from mechanically de-muscled backbones. De-muscled backbones were pre-treated with alkaline (0.04 N NaOH) followed by EDTA and 10 % ethanol for de-calcification and lipid extraction, respectively. Gelatine from pretreated backbones was extracted with 60 °C water. The amount of gelatine amino acids (sum of hydroxyproline, proline and glycine) was 43.4 ± 0.2 % of all amino acids in the gelatine. Extracted backbone gelatines showed film-forming ability. Gelatine films were obtained by casting procedure. Resulted salmon backbone 6 % gelatine and 30 % sorbitol films showed properties (e.g. water vapour permeability, colour difference, transparency value) similar to films obtained with commercial gelatine, indicating the capability of the extracted gelatines for its valorisation as edible coatings or bio-based film layers in packaging.

Comparison of Structural and Physicochemical Characteristics of Skin Collagen from Chum Salmon (Cold-Water Fish) and Nile Tilapia (Warm-Water Fish)

This study compared collagens from cold-water and warm-water fish for their structural, rheological, and functional properties, and explored their potential applications, aiming to realize the high-value utilization of marine biological resources. To this end, chum salmon skin collagen (CSSC) and Nile tilapia skin collagen (NTSC) were both successfully extracted. Collagens from the two species had different primary and secondary structures, with NTSC having a higher molecular weight, imino acid content, and α-helices and β-turns content. The denaturation temperatures were 12.01 °C for CSSC and 31.31 °C for NTSC. CSSC was dominated by viscous behavior and its structure varied with temperature, while NTSC was dominated by elastic behavior and its structure remained stable with temperature. Both collagens had good oil holding capacity, foaming capacity, and emulsifying activity, but NTSC had better water holding capacity and foaming and emulsifying stability. Their different properties make CSSC more suitable for the preservation of frozen and chilled foods and the production of sparkling beverages, and give NTSC greater potential in biofunctional materials and solid food processing.

Utilization of Lumpfish (Cyclopterus lumpus) Skin as a Source for Gelatine Extraction Using Acid Hydrolysis

Lumpfish (Cyclopterus lumpus) is an underutilized marine resource that is currently only being exploited for roe. Lumpfish skin was pre-treated with alkali (0.1M NaOH) and acid (0.1M HCl) at a skin to chemical ratio of 1:10 for 24 h at 5 °C to remove non-collagenous proteins and minerals. The pre-treated skin was washed, and gelatine was extracted with 0.1M of acetic acid at three different ratios (1:5, 1:10, and 1:15), time (12,18, and 24 h), and temperature combinations (12, 28, and 24 °C). The highest total extraction yield (>40%) was obtained with combinations of extraction ratios of 1:15 and 1:10 with a longer time (24 h) and higher temperature (18-24 °C). The highest gelatine content was obtained with an extraction period of 24 h and ratio of 1:10 (>80%). SDS-PAGE analysis confirmed the presence of type-I collagen. A rheological evaluation indicated melting and gelling temperatures, gel strength, and viscosity properties comparable to existing cold-water gelatine sources.