Effects of γ-polyglutamic acid on the gelling properties and non-covalent interactions of fish gelatin

Thermal stability of γ-PGA modified fish gelatin emulsion

BACKGROUND

Emulsions are thermally unstable systems. This research aimed to investigate the thermal stability of fish gelatin (FG) oil-in-water emulsions in the presence of poly-γ-glutamic acid (γ-PGA) as an additive after heat treatment. The study assessed how γ-PGA influences the thermal stability of FG emulsions over time, focusing on their properties, structure, and food application potential.

RESULTS

The incorporation of γ-PGA significantly enhanced the thermal stability of FG emulsions, preserving their morphology after heating. Emulsions containing 0.1% γ-PGA showed no significant changes after 24 h at 90 °C, while emulsions without γ-PGA experienced noticeable delamination. Rheological evaluations revealed that the energy storage modulus and loss modulus of FG-γ-PGA emulsions remained consistently higher than those of FG emulsions, regardless of heating duration. Particle size analysis indicated minimal changes for FG-γ-PGA emulsions (413 nm after 24 h) compared to a substantial increase for FG emulsions (1598 nm). After heating, FG-γ-PGA emulsions demonstrated significantly higher emulsifying activity index (EAI) (74 m2 g-1 versus 22.7 m2 g-1) and emulsifying stability index (ESI) (97% versus 76%). Additionally, the texture properties of meat mince formulated with FG-γ-PGA emulsions were comparable to those containing fat, showcasing their potential as a fat replacement.

CONCLUSION

The study concludes that γ-PGA enhances the thermal stability of FG emulsions, maintaining their integrity and improving functional properties under heat treatment. These findings offer valuable insights for the formulation of thermally stable emulsions, presenting promising opportunities for innovative applications in the food industry. © 2024 Society of Chemical Industry.

Oxidative regulation and cytoprotective effects of γ-polyglutamic acid on surimi sol subjected to freeze-thaw process

Frozen surimi sol incline to protein oxidation, but the quality control strategies based on oxidation remain limited. Hence, the antioxidant and cryoprotective effects of γ-polyglutamic acid (γ-PGA) on freeze-thawed salt-dissolved myofibrillar protein (MP) sol were investigated. Results showed that γ-PGA could effectively regulate protein oxidation of MP sol during freeze-thawing with lower carbonyl contents and less oxidative cross-linking. Meanwhile, γ-PGA primely maintained sol protein structures, showing reduction of 15.28% of salt soluble protein contents at γ-PGA addition of 0.04% under unoxidized condition. Additionally, compared to the control group without oxidation treatment, cooking loss of heat-induced gel with 0.04% γ-PGA decreased by 47.19%, while gel strength obviously increased by 57.22% respectively. Overall, moderate γ-PGA addition (0.04%) could inhibit protein oxidation of sol, further improving frozen stability of sol through hydrogen bonds and hydrophobic interaction, but excessive γ-PGA was adverse to sol quality due to severe cross-linking between γ-PGA and MP.

Effects of Maillard reaction of different monosaccharide-modified on some functional properties of fish gelatin

In this work, the effects of Maillard reaction of different monosaccharide-modified fish gelatin were studied. The changes of gel properties, rheology and structure of fish gelatin before and after modification were compared and analyzed, and oil-in-woter emulsions were prepared. The results showed that the five-carbon monosaccharide had stronger modification ability than the six-carbon monosaccharide, which was mainly due to the different steric hindrance of the amino acids in the nuclear layer and the outer layer to the glycosylation reaction. With the progress of the Maillard reaction, the color of fish gelatin gradually became darker. The attachment of sugar chains inhibited the gelation process of fish gelatin, decreased the gelation rate, changed the secondary structure, increased the content of β-turn or α-helix, increased the degree of fluorescence quenching, and enhanced the emulsifying properties and emulsion stability. This study provides useful information for the preparation of different types of monosaccharide-modified proteins and emulsions.

Rheology, physicochemical properties, and microstructure of fish gelatin emulsion gel modified by γ-polyglutamic acid

In this work, the effect of the addition of γ-polyglutamic acid (γ-PGA) on the rheology, physicochemical properties, and microstructure of fish gelatin (FG) emulsion gel was investigated. Samples of the emulsion gel were evaluated for rheological behavior and stability prior to gelation. The mechanical properties and water-holding capacity (WHC) of the emulsion were determined after gelation. The microstructure of the emulsion gel was further examined using confocal laser scanning microscopy (CLSM). The results indicated a gradual increase in the apparent viscosity and gelation temperature of the emulsion at a higher concentration of γ-PGA. Additionally, frequency scan results revealed that on the addition of γ-PGA, FG emulsion exhibited a stronger structure. The emulsion containing 0.1% γ-PGA exhibited higher stability than that of the control samples. The WHC and gel strength of the emulsion gel increased on increasing the γ-PGA concentration. CLSM images showed that the addition of γ-PGA modified the structure of the emulsion gel, and the droplets containing 0.1% γ-PGA were evenly distributed. Moreover, γ-PGA could regulate the droplet size of the FG emulsion and its size distribution. These findings suggest that the viscoelasticity and structure of FG emulsion gels could be regulated by adjusting the γ-PGA concentration. The γ-PGA-modified FG emulsion gel also exhibited improved rheology and physicochemical properties. The results showed that γ-PGA-modified FG emulsion gel may find potential applications in food, medicine, cosmetics, and other industries.

Discrimination and characterization of different ultrafine grinding times on the flavor characteristic of fish gelatin using E-nose, HS-SPME-GC-MS and HS-GC-IMS

Three different methods were used to identify and analyze the flavor of fish gelatin with different ultrafine grinding time (0, 2, 4 and 8 h). The results of electronic nose showed that overall flavor of the samples changed. HS-SPME-GC-MS identified 65 volatile compounds, including 18 aldehydes, 7 ketones, 7 alkanes, 11 alcohols, 8 esters, 7 phenols, and 7 acids. HS-GC-IMS identified 46 volatile compounds, including 21 aldehydes, 5 ketones, 5 alcohols, 6 esters, 7 acids, 1 ether, and 1 amine. The particle size analysis results indicate that the size distribution decreases from 918.97-1167.16 and 1388.81-1780.40 nm to 157.63-177.37 and 285.90-344.55 nm with the increased of grinding time. The SEM analysis results indicate that the change in flavor characteristics of FG is due to the different storage and release abilities of volatile compounds in FG with different particle sizes.

Gelatin Sponges with a Uniform Interoperable Pore Structure and Biodegradability for Liver Injury Hemostasis and Tissue Regeneration

Developing a hemostatic sponge that can effectively control bleeding from visceral injuries while guiding in situ tissue regeneration in incompressible wounds remains a challenge. Most of the existing hemostatic sponges degrade slowly, are relatively single-functioning, and cannot cope with complex environments. Herein, a biodegradable rapidly hemostatic sponge (GPZ) was created by dual-dynamic-bond cross-linking among Zn2+, protocatechualdehyde (PA)-containing catechol and aldehyde groups, and gelatin. GPZ had a uniformly distributed interconnected pore structure with excellent fluid absorption. It could effectively absorb the oozing blood and increase the blood concentration while stimulating platelet activation and accelerating blood coagulation. Compared to commercial hemostats, GPZ treatment significantly accelerated hemostasis in the rat liver defect model (∼0.33 min, ≥50% reduction in the hemostatic time) and in the rabbit liver defect model (∼1.02 min, ≥60% reduction in the hemostatic time). Additionally, GPZ had excellent antibacterial and antioxidant properties that effectively protected the wound from infection and excessive inflammation. In the liver regeneration model, GPZ significantly increased the rate of hepatic tissue repair and promoted rapid functional recovery without complications and adverse reactions. Overall, we designed a simple and effective biodegradable rapid hemostatic sponge with good clinical translational potential for treating lethal incompressible bleeding and promoting wound healing.

Gelatin scaffold ameliorates proliferation & stem cell differentiation into the hepatic like cell and support liver regeneration in partial-hepatectomized mice model

Stem cell-based tissue engineering is an emerging tool for developing functional tissues of choice. To understand pluripotency and hepatic differentiation of mouse embryonic stem cells (mESCs) on a three-dimensional (3D) scaffold, we established an efficient approach for generating hepatocyte-like cells (HLCs) from hepatoblast cells. We developed porous and biodegradable scaffold, which was stimulated with exogenous growth factors and investigated stemness and differentiation capacity of mESCs into HLCs on the scaffoldin-vitro. In animal studies, we had cultured mESCs-derived hepatoblast-like cells on the scaffold and then, transplanted them into the partially hepatectomized C57BL/6 male mice model to evaluate the effect of gelatin scaffold on hepatic regeneration. The 3D culture system allowed maintenance of stemness properties in mESCs. The step-wise induction of mESCs with differentiation factors leads to the formation of HLCs and expressed liver-specific genes, including albumin, hepatocyte nucleic factor 4 alpha, and cytokeratin 18. In addition, cells also expressed Ki67, indicating cells are proliferating. The secretome showed expression of albumin, urea, creatinine, alanine transaminase, and aspartate aminotransferase. However, the volume of the excised liver which aids regeneration has not been studied. Our results indicate that hepatoblast cells on the scaffold implanted in PH mouse indicates that these cells efficiently differentiate into HLCs and cholangiocytes, forming hepatic lobules with central and portal veins, and bile duct-like structures with neovascularization. The gelatin scaffold provides an efficient microenvironment for liver differentiation and regeneration bothin-vitroandin-vivo. These hepatoblasts cells would be a valuable source for 3D liver tissue engineering/transplantation in liver diseases.

Biomineralization-Inspired Anti-Caries Strategy Based on Multifunctional Nanogels as Mineral Feedstock Carriers

Background

Dentin caries remains a significant public concern, with no clinically viable material that effectively combines remineralization and antimicrobial properties. To address this issue, this study focused on the development of a bio-inspired multifunctional nanogel with both antibacterial and biomineralization properties.

Methods

First, p(NIPAm-co-DMC) (PNPDC) copolymers were synthesized from N-isopropylacrylamide (NIPAm) and 2-methacryloyloxyethyl-trimethyl ammonium chloride (DMC). Subsequently, PNPDC was combined with γ-polyglutamic acid (γ-PGA) through physical cross-linking to form nanogels. These nanogels served as templates for the mineralization of calcium phosphate (Cap), resulting in Cap-loaded PNPDC/PGA nanogels. The nanogels were characterized using various techniques, including TEM, particle tracking analysis, XRD, and FTIR. The release properties of ions were also assessed. In addition, the antibacterial properties of the Cap-loaded PNPDC/PGA nanogels were evaluated using the broth microdilution method and a biofilm formation assay. The remineralization effects were examined on both demineralized dentin and type I collagen in vitro.

Results

PNPDC/PGA nanogels were successfully synthesized and loaded with Cap. The diameter of the Cap-loaded PNPDC/PGA nanogels was measured as 196.5 nm at 25°C and 162.3 nm at 37°C. These Cap-loaded nanogels released Ca2+ and PO43- ions quickly, effectively blocking dental tubules with a depth of 10 μm and promoting the remineralization of demineralized dentin within 7 days. Additionally, they facilitated the heavy intrafibrillar mineralization of type I collagen within 3 days. Moreover, the Cap-loaded nanogels exhibited MIC50 and MIC90 values of 12.5 and 50 mg/mL against Streptococcus mutans, respectively, with an MBC value of 100 mg/mL. At a concentration of 50 mg/mL, the Cap-loaded nanogels also demonstrated potent inhibitory effects on biofilm formation by Streptococcus mutans while maintaining good biocompatibility.

Conclusion

Cap-loaded PNPDC/PGA nanogels are a multifunctional biomimetic system with antibacterial and dentin remineralization effects. This strategy of using antibacterial nanogels as mineral feedstock carriers offered fresh insight into the clinical management of caries.

Comparative investigations of various modification methods on the gelling, rheological properties and mechanism of fish gelatin

In this study, κ-carrageenan(κC) and Transglutaminase (TG) were used to modify fish gelatin (FG). Three types of modified gelatin groups FG-κC, FG-TG and FG-κC-TG were prepared. The results showed that the gel strength and textural properties of FG gels were greatly enhanced by κC modification and κC-TG complex modification, whilst pure TG modification weakened the gelling properties. And the pure 0.1 % κC modified FG had the highest gel strength and hardness, respectively. Rheological behavior showed that the complex modified FG samples had the highest viscosity, gelling points, melting points and G'∞. Fourier infrared spectra and LF-NMR analysis showed that κC and κC-TG modification respectively improved the contents of hydrogen and isopeptide that decreased the water mobility but stabilized the helical structure of gelatin gels. Fluorescence intensity showed that three types of modification decreased fluorescence intensity. While, the formation of aggregates and denser gel networks decreased in vitro digestibility of FG.

Repurposing fish waste into gelatin as a potential alternative for mammalian sources: A review

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, film-forming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13-19°C to 23-25°C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30°C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.

3D Printing of Shiitake Mushroom Incorporated with Gums as Dysphagia Diet

With the speeding tendency of aging society, the population experienced dysphagia is increasing quickly. Desirable dysphagic diets should be safe, visually appealing and nutritious. 3D printing allows for creation of personalized nutritious foods with regular-like appearance. Shiitake mushroom, rich in protein and bioactive compounds, is suitable for elderly, but its hard texture was not friendly to the elderly with dysphagia. This study investigated the feasibility of production of dysphagic product using shiitake mushroom by 3D printing with various gums addition, including arabic gum (AG), xanthan gum (XG) and k-carrageenan gum (KG) at concentrations of 0.3%, 0.6% and 0.9% (w/w). Data suggested that XG and KG incorporation significantly increased inks’ mechanical strength by decreasing water mobility and promoting the formation of hydrogen bond, enabling 3D printed objects with great self-supporting capacity. The XG containing and KG-0.3% samples were categorized into level 5—minced and moist dysphagia diet within international dysphagia diet standardization initiative (IDDSI) framework. AG addition decreased mechanical strength and viscosity, hardness and self-supporting capacity of 3D printed constructions. AG-0.3% and AG-0.6% samples could not be classified as dysphagia diets based on IDDSI tests. This study provides useful information for dysphagia diet development with appealing appearance by 3D printing.

Reversibility of the gel, rheological, and structural properties of alcohol pretreated fish gelatin: Effect of alcohol types

The reversibility of gel property of alcohol (methanol, ethanol)-pretreated fish gelatin (FG) were investigated through removing alcohol solutions by freeze drying. Results showed that the gel strength and the hardness of FG could be retained (1%, 40%) or even improved (1% methanol) using low or high concentration alcohol solutions, while decreased in medium concentration alcohol solutions. Compared with untreated FG, rheology results showed that, all alcohol solutions pretreated FG had lower apparent viscosity, while higher alcohol solutions pretreated ones decreased the gel and melt points and shorten the gelation time. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis showed that methanol pretreated FG had the higher α contents than those of ethanol pretreated. Circular dichroism spectra results indicated that β-sheet could be decreased after removing ethanol solutions, whereas the β-sheet increased after removing the methanol solutions. Moreover, low field nuclear magnetic resonance relaxation test showed that pretreated FG had lower transverse relaxation times of internal water (T₂₁ and T₂₂ ) compared to that of the untreated FG. Overall, FG still retains higher gel properties after removing the low or high alcohol concentrations.

Microbial transglutaminase (MTGase) modified fish gelatin-γ-polyglutamic acid (γ-PGA): Rheological behavior, gelling properties, and structure

Fish gelatin (FG) has been extensively studied as a potential substitute for mammal gelatin. However, FG often requires different modification methods to change its physical and chemical properties due to its low gelling properties. Here, γ-polyglutamic acid (γ-PGA) and microbial transglutaminase (MTGase) were combined to modify FG to improve its gelling properties. The γ-PGA at 0.04% (w/v) and MTGase of different concentrations (0.02-0.08%, w/v) were used to modify FG, and the effects of complex modification on the gelling properties and structure of FG were studied. When the MTGase content was 0.08% (w/v), FG had the best gelling properties. In addition, the complex modification of MTGase and γ-PGA hindered the formation of the triple helix during the FG gel process. This reduced the gel rate, but significantly increased its viscosity. A schematic model was also proposed to illustrate the complex modifications of FG by MTGase and γ-PGA.