Research on rapid gelatinization of rabbit skin collagen as effect of acid treatment

Clean and sustainable extraction of gelatin: Effects of microwave and freeze-thaw on the crosslinking degree and hydrogen bond of fish skin collagen

The traditional gelatin extraction methods (acid-base) may hinder to their green applications due to mass energy consumption and pollution. Herein, we constructed a clean and sustainable gelatin extraction method, investigated the molecular mechanism of microwave treatment (0-360 min) and freeze-thaw on the gelatin extraction from the perspective of the crosslinking degree and hydrogen bonds. Microwave (0-60 min) can improve the hydrolysis degree (DH) and expose more enzyme cleavage sites of collagen by destroying the intramolecular and intermolecular covalent crosslinking. Freeze-thaw loosened the collagen structure mainly by destroying hydrogen bonds, further increased degree of freedom, DH and enzyme cleavage sites, improved the gelatin yield and gel strength. However, the long-term microwave treatment (60-360 min) severely damaged the covalent crosslinking, increased the DH and enzyme cleavage sites. Freeze-thaw further loosened the collagen structure, caused the rapid dissolution and degradation of subunit, improved the gelatin yield and reduced the gels strength.

Study on the Structural Changes of Boneless Chicken Claw Collagen and Its Effect on Water Retention Performance

The purpose of this study was to explore the water retention mechanism of chicken claws by detecting the structural changes in collagen in boneless chicken claws under different expansion rates. Firstly, boneless chicken claw collagen with different expansion rates (0%, 10%, 20%, 30%, 40%, 50%) was extracted by the acid-enzyme complex method, and the changes in collagen were determined by scanning electron microscopy (SEM), ultraviolet spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), low-field nuclear magnetic resonance LF-NMR) and surface hydrophobicity to explore the mechanism that leads to changes in the water retention performance. The results of scanning electron microscopy showed that with the increase in the expansion rate, collagen molecules showed curling, shrinking, breaking and crosslinking, forming a loose and irregular pore-like denatured collagen structure. UV analysis showed that the maximum absorption wavelength of chicken claw collagen was blue shifted under different expansion rates, and the maximum absorption peak intensity increased first and then decreased with the increase in expansion rate. The FTIR results showed that collagen had obvious characteristic absorption peaks in the amide A, B, I, II and III regions under different expansion rates, and that the intensity and position of the characteristic absorption peaks changed with the expansion rate. The results of the CD analysis showed that collagen at different expansion rates had obvious positive absorption peaks at 222 nm, and that the position of negative absorption peaks was red shifted with the increase in expansion rate. This shows that the expansion treatment makes the collagen of chicken claw partially denatured, and that the triple helix structure becomes relaxed or unwound, which provides more space for the combination of water molecules, thus enhancing the water absorption capacity of boneless chicken claw. The results of the surface hydrophobicity test showed that the surface hydrophobicity of boneless chicken claw collagen increased with the increase in expansion rate and reached the maximum at a 30% expansion rate, and then decreased with the further increase in the expansion rate. The results of LF-NMR showed that the water content of boneless chicken claws increased significantly after the expansion treatment, and that the water retention performance of chicken claws was further enhanced with the increase in the expansion rate. In this study, boneless chicken claws were used as raw materials, and the expansion process of boneless chicken claws was optimized by acid combined with a water-retaining agent, which improved the expansion rate of boneless chicken claws and the quality of boneless chicken claws. The effects of the swelling degree on the collagen structure, water absorption and water retention properties of boneless chicken claws were revealed by structural characterization. These findings explain the changes in the water retention of boneless chicken claws after expansion. By optimizing the expansion treatment process, the water retention performance and market added value of chicken feet products can be significantly improved, which is of great economic significance.

A multifunctional soybean protein isolates crosslinked gelatins composite mulch film: Fabrication, characterization, and application

The development of sustainable agriculture has boosted an increase in demand for biodegradable and multifunctional biomass-based mulch films. Herein, a sort of eco-friendly and multifunctional soybean protein isolates crosslinked gelatins (SPI-c-Gel) composite mulch films were elaborately designed through the Schiff base reaction. The formation of physical entanglement and chemical cross-linking between the molecular chains of SPI and Gel could effectively dissipate the loading energy and thereby strengthen the resistance of the composite mulch films to water penetration. Specifically, the maximum tensile strain and tensile stress were observed to increase from 4.05 MPa at 73.3 % for pure SPI film to 14.7 MPa at 151 % for optimized SPI-c-Gel0.3 mulch film. The swelling rate in water declined from 280 % for pure SPI film to 141 % for SPI-c-Gel0.3 composite film. Furthermore, the fabricated composite mulch film exhibited satisfied water retention, urea slow-release properties, and biodegradability. The application experiments of SPI-c-Gel0.3 composite mulch have shown that the seeds grew faster when cabbage seeds were covered by such mulch film during seed germination. Our findings provide a novel strategy for regulating the physical and chemical properties of biopolymer-based multifunctional mulch films, which may be employed to promote the development of sustainable agriculture.

Valorization of Seafood Waste for Food Packaging Development

Packaging plays a crucial role in protecting food by providing excellent mechanical properties as well as effectively blocking water vapor, oxygen, oil, and other contaminants. The low degradation of widely used petroleum-based plastics leads to environmental pollution and poses health risks. This has drawn interest in renewable biopolymers as sustainable alternatives. The seafood industry generates significant waste that is rich in bioactive substances like chitin, chitosan, gelatins, and alginate, which can replace synthetic polymers in food packaging. Although biopolymers offer biodegradability, biocompatibility, and non-toxicity, their films often lack mechanical and barrier properties compared with synthetic polymer films. This comprehensive review discusses the chemical structure, characteristics, and extraction methods of biopolymers derived from seafood waste and their usage in the packaging area as reinforcement or base materials to guide researchers toward successful plastics replacement and commercialization. Our review highlights recent advancements in improving the thermal durability, mechanical strength, and barrier properties of seafood waste-derived packaging, explores the mechanisms behind these improvements, and briefly mentions the antimicrobial activities and mechanisms gained from these biopolymers. In addition, the remaining challenges and future directions for using seafood waste-derived biopolymers for packaging are discussed. This review aims to guide ongoing efforts to develop seafood waste-derived biopolymer films that can ultimately replace traditional plastic packaging.

Effect of low-frequency ultrasound-assisted acid extraction on gel properties and structural characterization of sheep's hoof gelatin

In this study, we investigated the effects of various low-frequency ultrasound-assisted extraction processes, including ultrasound-assisted acid-soaked water bath extraction (UAW), ultrasound-assisted water bath extraction after acid soaking (AUW), acid-soaked water bath extraction followed by ultrasonics (AWU), and acid-soaked water bath extraction without ultrasound (CON), on the structural properties, thermal stability, gel properties, and microstructure of sheep's hoof gelatin. The results revealed that the primary components of sheep's hoof gelatin consisted of α1-chain, α2-chain (100-135 kDa), and β-chain. In addition, it was observed that among the three sonication groups, sheep's hoof gelatin extracted in the AUW group exhibited the highest yield (27.16 ± 0.41 %), the best gel strength (378.55 ± 7.34 g), and higher viscosity at the same shear rate. The gelling temperature (25.38 ± 0.45 °C) and melting temperature (32.28 ± 0.52 °C) of sheep's hoof gelatin in the AUW group were significantly higher than those in the other groups (p > 0.05). Moreover, our experiments revealed that the sequence of low-frequency ultrasonic pretreatment processes was a crucial factor influencing the gel properties and structural characteristics of sheep's hoof gelatin. Specifically, the acid treatment followed by the ultrasound-assisted approach in the AUW group yielded high-quality and high-yield sheep's hoof gelatin.

Construction and evaluation of environment-friendly POSS multi-crosslinked mulch film based on bone gelatin

The non-degradable traditional polyethylene (PE) mulch film has caused great harm to both the ecological environment as well as human health. Therefore, the biodegradable bone gelatin (B-Gel) was innovatively selected to build the mulch film. To further enhance the toughness of the B-Gel mulch films, a POSS star-shaped polymer/bone gelatin (P(POSS-AGE-HEA)/B-Gel) composite was prepared by introducing POSS star-shaped polymer into B-Gel via in situ polymerization using polyhedral oligomeric silsesquioxane (POSS), allyl glycidyl ether (AGE) and hydroxyethyl acrylate (HEA) as raw material, and then was cast to obtain the P(POSS-AGE-HEA)/B-Gel mulch film. The epoxy group of POSS star-shaped polymer with the -COOH and -NH2 of B-Gel forms a covalent bond, and the hydroxyl group with the active groups of B-Gel forms hydrogen bonds. Meanwhile, the multiple side chains of POSS star-shaped polymer are intertwined with B-Gel. These covalent and hydrogen bonds as sacrificial bonds for effective energy dissipation giving the bone gelatin-based film excellent mechanical properties with a tensile strength of 7.56 ± 0.64 MPa and elongation at break of 197.49 ± 17.63 %. Additionally, it also demonstrated sound water vapor barrier, surface hydrophobicity, light transmittance and the effect of facilitating the growth and germination ratio (93.75 %) of wheat.

Effect of different dehydration methods on the properties of gelatin films

The properties of gelatin film fabricated by ethanol precipitation effect dehydration, Hofmeister effect dehydration and hot air drying dehydration were investigated. The results revealed that the mechanical properties were significantly improved by ethanol precipitation and Hofmeister effect. The tensile strength and elongation at break of the film prepared by ethanol precipitation were increased by 83.28% (20% gelatin concentration) and 122.42% (5% gelatin concentration) respectively compared with that of hot air-dried gelatin film. The water contact angle was increased and water solubility was reduced by ethanol precipitation, which could attribute to the formation of compact structure, more triple helix content, and non-covalent interactions. However, the water contact angle of Hofmeister effect fabricated films was decreased compared with that of hot air drying owing to the adhesion of ammonium sulfate. Moreover, ethanol precipitation effect improved the color difference and opacity due to the ethanol decolorization effect.

Distinct Retrotransposon Evolution Profile in the Genome of Rabbit (Oryctolagus cuniculus)

Although the rabbit genome has already been annotated, it is mobilome remains largely unknown. Here, multiple pipelines were used to de novo mine and annotate the mobilome in rabbit. Four families and 19 subfamilies of LINE1s, two families and nine subfamilies of SINEs, and 12 ERV families were defined in rabbit based on sequence identity, structural organization, and phylogenetic tree. The analysis of insertion age and polymerase chain reaction suggests that a number of families are very young and may remain active, such as L1B, L1D, OcuSINEA, and OcuERV1. RepeatMasker annotation revealed a distinct transposable element landscape within the genome, with approximately two million copies of SINEs, representing the greatest proportion of the genome (19.61%), followed by LINEs (15.44%), and LTRs (4.11%), respectively, considerably different from most other mammal mobilomes except hedgehog and tree shrew, in which LINEs have the highest proportion. Furthermore, a very high rate of insertion polymorphisms (>85%) for the youngest subfamily (OcuSINEA1) was identified by polymerase chain reaction. The majority of retrotransposon insertions overlapped with protein-coding regions (>80%) and lncRNA (90%) genes. Genomic distribution bias was observed for retrotransposons, with those immediately upstream (-1 kb) and downstream (1 kb) of genes significantly depleted. Local GC content in 50-kb widows had significantly negative correlations with LINE (rs=-0.996) and LTR (rs=-0.829) insertions. The current study revealed a distinct mobilome landscape in rabbit, which will assist in the elucidation of the evolution of the genome of lagomorphs, and even other mammals.

Effect of drying methods on the solubility and amphiphilicity of room temperature soluble gelatin extracted by microwave-rapid freezing-thawing coupling

The effect of three drying methods (hot air, freeze and spray drying) on the solubility and amphiphilicity of gelatin were investigated and compared. Results showed spray drying gelatin (SDG) and hot air drying gelatin (HDG) showed the lowest and best solubility, respectively. This phenomenon was attributed to the degree of subunits degradation and hydrophobicity. The HDG showed an obvious degradation during the hot air drying and displayed the strongest hydrophilicity, while SDG showed a slight degradation and strongest hydrophobicity. The results of wettability showed that SDG had a better amphiphilicity (92.48°) in comparison with HDG (57.7°) and freeze drying gelatin (VDG, 77.53°), which can effectively reduce the interfacial tension of gelatin, thus significantly improving the stability of foam and emulsion (p < 0.05). These results suggested the drying methods can adjust the amphiphilicity of gelatin, and the SDG displayed a better amphiphilicity, showing good potential applications in foam and emulsion.

Improved solubility and interface properties of pigskin gelatin by microwave irradiation

In this study, the microwave irradiation as a green approach was applied to improve the properties (mainly solubility and interface properties) of pigskin gelatin. The results showed that the solubility of pigskin gelatin was improved obviously at room temperature (25 °C) due to the destruction of polymer subunits. Furthermore, the exposure of more hydrophobic groups in microwave-irradiated gelatin increased its hydrophobicity, consequently improving the amphiphilic property and the interfacial properties of gelatin. The results of interface behavior showed that the interfacial tension of microwave-irradiated gelatin was reduced obviously with the extension of irradiation time (0-30 min), which is more beneficial to adsorption of gelatin molecules at the interface, thus resulting in a significant increase of adsorption rate (AP) from 56.13% (0 min) to 91.87% (30 min). Correspondingly, the foaming and emulsifying properties of gelatin were also improved significantly (p < 0.05). This study would promote the development of food-grade foam and emulsion based on pigskin gelatin by adjusting solubility and interface properties.

Sustainable Rabbit Skin Glue to Produce Bioactive Nanofibers for Nonactive Wound Dressings

This paper assessed the collagen glue (Col) from rabbit skin for use as a raw material in combination with different water-based dispersants of antimicrobial agents such as ZnO NPs, TiO₂ NPs doped with nitrogen and Ag NPs (TiO₂-N-Ag NPs), and chitosan (CS) for the production of biocompatible and antimicrobial nanofibers. The electrospun nanofibers were investigated by scanning electron microscopy (SEM), attenuated total reflectance in conjunction with Fourier-transform infrared spectroscopy (ATR-FT-IR) analyses and antioxidant activity. The biocompatibility of electrospun nanofibers was investigated on cell lines of mouse fibroblast NCTC (clone L929) using MTT test assays. Antimicrobial activity was performed against Escherichia coli and Staphylococcus aureus bacteria and Candida albicans pathogenic fungus. Electrospun antimicrobial nanofibers based on collagen glue achieved reduction in the number of viable microorganisms against both fungi and bacteria and exhibited multiple inhibitory actions of fungal and bacterial strains. The electrospun nanofibers showed average dimension sizes in the range of 30–160 nm. The results indicated that both Col/TiO₂-N-Ag NPs and Col/CS formulations are suitable for cell proliferation and may be useful for producing of nonactive wound dressings.

The effects of enzymatically aided acid-swelling process on gelatin extracted from fish by-products

The objective of this study was to investigate the effects of the enzymatic aided acid-swelling process on gelatin obtained from fish by-products. For this purpose, gelatin was extracted by an acidic swelling procedure in the presence of protease extracted from Rainbow trout pyloric caeca. The yield of gelatin extraction and the most important physicochemical characteristics of the fish gelatin samples were investigated and compared with those of commercial bovine gelatin (CBG). The yields of gelatin from Epinephelus coioides skin (ESG) either with or without crude protease from pyloric caeca (15 units/g alkaline treated) were 14.98% and 50.89%, respectively. The yields of gelatin from Cyprinus carpio scales (CSG) with crude protease from pyloric caeca (15 units/g) were 49.97%. The gel strength of the CSG (259.66 g) was significantly higher than that of CBG (228.30 g) and ESG (187.75 g). Similarly, the gelling and melting points, foaming capacity and stability, and the SDS-PAGE pattern of gelatins were compared. The electrophoretic pattern confirmed the results of gel strength which was due to the narrower alpha and beta bands in fish skin and commercial bovine gelatins than that of fish scales gelatin. The results of this research showed that the production of high-quality gelatin can be achieved by the enzymatically aided acid-swelling procedure from fish scales and skin.

Food-Grade Gelatin Nanoparticles: Preparation, Characterization, and Preliminary Application for Stabilizing Pickering Emulsions

In this paper, the food-grade gelatin nanoparticles (GNPs) were prepared by a two-step desolvation method and using genipin as a cross-linker. The GNPs with narrow size distribution and good dispersion could be obtained only at pH 12. The effect of the genipin dosage (8-12 wt%) on the GNPs was systematically investigated. The results showed that the cross-linking degree of the GNPs increased with the increasing dosage of genipin, thus leading to a more obvious cross-linking morphology observed from scanning electron microscope (SEM). The obtained GNPs showed a good dispersibility with a size range of 386-438 nm. However, the GNPs cross-linked by 8 wt% genipin dosage revealed a relatively higher size because of the aggregation induced by hydrogen bond. The 10 wt% group had good thermal stability and storage stability. The optical microscopy results showed that the Pickering emulsions (30-50 vol% internal phase) stabilized by the GNPs had good uniformity and stability, even after 30 days of storage time, suggesting that the stable GNPs had great potential in food-grade Pickering emulsions.