Elucidation of aqueous interactions between fish gelatin and sodium alginate

Copper nanoparticles loaded gelatin/ polyvinyl alcohol/ guar gum-based 3D printable multimaterial hydrogel for tissue engineering applications

Hydrogels are becoming increasingly significant in tissue engineering because of their numerous benefits, including biocompatibility, biodegradability, and their ability to provide a supportive structure for cell proliferation. This study presents the synthesis and characterization of a new multimaterial hydrogel with 3D-printing capabilities composed of copper nanoparticle-reinforced gelatin, polyvinyl alcohol (PVA), and guar gum-based biomaterials intended for tissue engineering applications. Combining CuNPs aims to enhance the hydrogel's antibacterial properties, mechanical strength, and bioactivity, which are essential for successful tissue regeneration. Hydrogels are chemically cross-linked with glyoxal and analyzed through different assessments to examine the compressive behavior, surface morphology, sorbing capacity, biocompatibility, thermal stability, and degradation properties. The results demonstrated that including CuNPs significantly improved the hydrogel's compressive modulus (4.18 MPa) for the hydrogel with the CuNPs and provided better antibacterial activity against common pathogens with controlled degradation. All the hydrogels exhibited a lower coefficient of friction, which was below 0.1. In vitro cell culture studies using chondrocytes indicated that the CuNPs-loaded hydrogel supported cell proliferation and growth of chondrogenic genes such as collagen type II (COL2) and aggrecan (ACAN). The biocompatibility and enhanced mechanical properties of the multimaterial hydrogel make it a promising candidate for developing customized, patient-specific tissue engineering scaffolds.

Preparation, Optimization, and Characterization of Bovine Bone Gelatin/Sodium Carboxymethyl Cellulose Nanoemulsion Containing Thymol

The aim of this study is to produce a biodegradable food packaging material that reduces environmental pollution and protects food safety. The effects of total solids content, substrate ratio, polyphenol content, and magnetic stirring time on bovine bone gelatin/sodium carboxymethylcellulose nanoemulsion (BBG/SCMC-NE) were investigated using particle size, PDI, turbidity, rheological properties, and zeta potential as evaluation indexes. The micro, structural, antioxidant, encapsulation, and release properties were characterized after deriving its optimal preparation process. The results showed that the nanoemulsion was optimally prepared with a total solids content of 2%, a substrate ratio of 9:1, a polyphenol content of 0.2%, and a magnetic stirring time of 60 min. SEM showed that the nanoemulsion showed a dense and uniform reticulated structure. FTIR and XRD results showed that covalent cross-linking of proteins and polysaccharides altered the structure of gelatin molecular chains to a more compact form but did not change its semi-crystalline structure. DSC showed that the 9:1 BBG/SCMC-NE had a higher thermal denaturation temperature and greater thermal stability, and its DPPH scavenging rate could reach 79.25% and encapsulation rate up to 90.88%, with excellent slow-release performance. The results of the study provide basic guidance for the preparation of stable active food packaging with excellent properties.

Development of polysaccharide-complexed nano-sized rice protein dispersion

The objective of this study was to improve water solubility of the rice protein (RP) by forming complexes with anionic polysaccharides, such as sodium alginate (SA) and xanthan gum (XG). In addition, utilization of the RP complexes as an emulsifier was evaluated. The prepared RP-SA or RP-XG complexes were analyzed by measuring their particle size, ζ-potential, and water solubility as well as by confocal laser scanning microscopy. The formation of a complex between RP-SA and RP-XG improved the water solubility and dispersibility of RP over a wide range of pH values (3, 5, 7, and 9). Confocal fluorescence images showed that the aggregation of RP molecules was prevented by the formation of complexes between RP and polysaccharides. When soybean oil-in-water emulsions were prepared with complexes, RP-SA (ratio 4:1) and RP-XG(ratio 4:1) complex-stabilized emulsions were stable for 4 weeks of storage.

A Review of Chondroitin Sulfate's Preparation, Properties, Functions, and Applications

Chondroitin sulfate (CS) is a natural macromolecule polysaccharide that is extensively distributed in a wide variety of organisms. CS is of great interest to researchers due to its many in vitro and in vivo functions. CS production derives from a diverse number of sources, including but not limited to extraction from various animals or fish, bio-synthesis, and fermentation, and its purity and homogeneity can vary greatly. The structural diversity of CS with respect to sulfation and saccharide content endows this molecule with distinct complexity, allowing for functional modification. These multiple functions contribute to the application of CS in medicines, biomaterials, and functional foods. In this article, we discuss the preparation of CS from different sources, the structure of various forms of CS, and its binding to other relevant molecules. Moreover, for the creation of this article, the functions and applications of CS were reviewed, with an emphasis on drug discovery, hydrogel formation, delivery systems, and food supplements. We conclude that analyzing some perspectives on structural modifications and preparation methods could potentially influence future applications of CS in medical and biomaterial research.

Phase Behavior of Aqueous Mixtures of Sodium Alginate with Fish Gelatin: Effects of pH and Ionic Strength

The phase behavior of aqueous mixtures of fish gelatin (FG) and sodium alginate (SA) and complex coacervation phenomena depending on pH, ionic strength, and cation type (Na⁺, Ca²⁺) were studied by turbidimetric acid titration, UV spectrophotometry, dynamic light scattering, transmission electron microscopy and scanning electron microscopy for different mass ratios of sodium alginate and gelatin (Z = 0.01-1.00). The boundary pH values determining the formation and dissociation of SA-FG complexes were measured, and we found that the formation of soluble SA-FG complexes occurs in the transition from neutral (pH_c) to acidic (pH_φ1) conditions. Insoluble complexes formed below pH_φ1 separate into distinct phases, and the phenomenon of complex coacervation is thus observed. Formation of the highest number of insoluble SA-FG complexes, based on the value of the absorption maximum, is observed at рH_opt and results from strong electrostatic interactions. Then, visible aggregation occurs, and dissociation of the complexes is observed when the next boundary, pH_φ2, is reached. As Z increases in the range of SA-FG mass ratios from 0.01 to 1.00, the boundary values of рН_c, рH_φ1, рH_opt, and рH_φ2 become more acidic, shifting from 7.0 to 4.6, from 6.8 to 4.3, from 6.6 to 2.8, and from 6.0 to 2.7, respectively. An increase in ionic strength leads to suppression of the electrostatic interaction between the FG and SA molecules, and no complex coacervation is observed at NaCl and CaCl₂ concentrations of 50 to 200 mM.

Physicochemical and functional properties of capsaicin loaded cricket protein isolate and alginate complexes

As people become more aware of the health benefits of foods and their nutritional benefits for preventing diseases and promoting health, the demand for functional foods rich in proteins, fiber, and bioactives like capsaicin (CAP) is constantly rising. This study hypothesized that the electrostatic complexes developed by cricket protein isolate (CPI) and alginate (AL) could be utilized to encapsulate CAP, making it more water-soluble and protecting it at acidic pHs. Quantitative analysis revealed that CAP was efficiently encapsulated into the CPI-AL complexes with a maximum encapsulation efficiency of 91%, improving its aqueous solubility 45-fold. In vitro release tests showed that CAP was retained at acidic pHs (3.0 and 5.0) in CPI-AL complexes but released steadily at neutral pH (7.4), which will protect CAP in the stomach while enabling its release in the small intestine. Moreover, the antioxidant activity of CAP-CPI-AL complexes was superior to that of their individual bare equivalents. The complexes also demonstrated enhanced emulsifying capabilities and stability at acidic pHs (2.0-5.0) as the CPI fraction in the complexes increased. Our findings thus contribute to the growing body of knowledge that validates protein-polysaccharide complexation as a promising strategy for developing edible delivery systems.

pH-induced complex coacervation of fish gelatin and carboxylated chitosan: phase behavior and structural properties

The aim of this study was to investigate the phase behavior and structural properties of fish gelatin complex coacervation with carboxylated chitosan as a function of pH by varying the amount of carboxylated chitosan added (0-0.25%, w/v) while keeping the fish gelatin concentration constant at 0.667% (w/v). Zeta potential indicated that electrostatic interaction drove the complex coalescence of fish gelatin and carboxylated chitosan to form soluble or insoluble complexes. The turbidity of the fish gelatin-carboxylated chitosan complex system was greatest at a carboxylated chitosan concentration of 0.2%. UV and fluorescence spectroscopy indicated that the carboxylated chitosan changed the tertiary conformation of fish gelatin. Circular dichroism showed that complexation of fish gelatin with carboxylated chitosan resulted in a shift from the α-helix to the β-sheet structure of fish gelatin. In particular, at pH 5, the fish gelatin complexed with carboxylated chitosan had a disordered structure. X-ray diffraction and scanning electron microscopy of the composite coacervates both investigated that electrostatic interaction between the two replaced molecular interaction within the carboxylated chitosan to form a new lamellar porous structure. These findings may in future enable the use of fish gelatin-carboxylated chitosan complex systems in the design of new food matrices.

Influence of fish skin gelatin-sodium alginate complex stabilized emulsion on benzyl isothiocyanate stability and digestibility in vitro and in vivo

BACKGROUND

An emulsion delivery system for benzyl isothiocyanate (BITC) was prepared using fish skin gelatin (FSG) and sodium alginate (Alg). The effects of the FSG-Alg complex on the emulsion stability and BITC release pattern from the emulsion were investigated in vitro and in vivo.

RESULTS

The storage stability and embedding rate of the 10 g kg^-1 FSG and 2.5 g kg^-1 Alg (FSG-Alg) emulsion were the highest among all samples. The FSG-Alg complex provided BITC a better protection during in vitro digestion. The microstructure of the FSG-Alg emulsions was more stable during in vitro digestion, and the bioaccessibility and retention rate of BITC were much higher compared to those of the FSG emulsion. The results of the ex vivo everted gut sac of rat intestine study showed that the FSG-Alg emulsion significantly increased the BITC absorption rate in the duodenum.

CONCLUSION

The FSG-Alg emulsion delivery system is a highly stable system for the delivery of BITC that improves the bioaccessibility of BITC and promotes its absorption in the duodenum. © 2022 Society of Chemical Industry.

Intermolecular Interactions in the Formation of Polysaccharide-Gelatin Complexes: A Spectroscopic Study

Gelatin, due to its gelling and stabilizing properties, is one of the widely used biopolymers in biotechnology, medicine, pharmaceuticals, and the food industry. One way to modify the characteristics of gelatin is molecular modification by forming non-covalent polyelectrolyte complexes with polysaccharides based on the self-organization of supramolecular structures. This review summarizes recent advances in the study of various types and the role of intermolecular interactions in the formation of polysaccharide-gelatin complexes, and conformational changes in gelatin, with the main focus on data obtained by spectroscopic methods: UV, FT-IR, and 1H NMR spectroscopy. In the discussion, the main focus is on the complexing polysaccharides of marine origin-sodium alginate, κ-carrageenan, and chitosan. The prospects for creating polysaccharide-gelatin complexes with desired physicochemical properties are outlined.

Unraveling the phase behavior of cricket protein isolate and alginate in aqueous solution

The associative phase behavior of cricket protein isolate (CPI) and sodium alginate (AL) in aqueous solutions was explored using turbidimetry, methylene blue spectroscopy, zeta potentiometry, dynamic light scattering, and confocal microscopy as a function of pH, biopolymer ratio, total biopolymer concentration (C_T), and ionic strength. When both biopolymers had net-negative charges, soluble complexes formed between pH 6.0 and 8.0, however when both biopolymers had opposing net charges, insoluble complexes formed as complex coacervates below pH 5.5, defined as pH_φ1, followed by precipitates below another critical pH 3.0 (pH_p). Increasing the CPI:AL weight ratio or C_T facilitated complex formation, and the addition of salts (NaCl/KCl) had a salt-enhancement and salt-reduction impact at low and high salt concentrations, respectively. Ionic interactions between oppositely charged CPI and AL were mainly responsible for the formation of their insoluble complexes, while hydrogen bonding and hydrophobic interactions also played significant roles.

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.

Interaction between Negatively Charged Fish Gelatin and Cyclodextrin in Aqueous Solution: Characteristics and Formation Mechanism

The effect that ratios of fish gelatin (FG) to α/β/γ cyclodextrins (α, β, γCDs) had on the phase behavior of a concentrated biopolymer mixture were comparatively investigated. This showed that the formed biopolymer mixture had the highest gel strength at ratios of FG–CD = 90:10. FG could interact with CDs to form stable soluble complexes with lower values of turbidity, particle size and ζ-potential. All of the FG–CD mixture solutions exhibited pseudo-plastic behaviors, and FG–αCD samples had the highest viscosity values than others. The addition of CDs could unfold FG molecules and make conformation transitions of FG from a random coil to β-turn, leading to the environmental change of hydrophobic residues and presenting higher fluorescence intensity, especially for βCDs. FTIR results revealed that the formation of intermolecular hydrogen bonds between FG and CD could change the secondary structure of FG. These findings might help further apply FG–CD complexes in designing new food matrixes.

Fabrication and performance evaluation of pectin-fish gelatin-resveratrol preservative films

Resveratrol-loaded fish gelatin (FG)-low methoxyl pectin (LMP) composite films with different FG:LMP mass ratios were prepared and evaluated as food packaging materials. With increasing FG contents, the water solubility of the films decreased. Moreover, the UV (315-400 nm) blocking efficiency and opacity increased with increasing LMP contents. The elongation of the films at breaking and tensile strengths were adjusted using the ratio of FG and LMP. The lowest water vapour permeability was observed at an FG:LMP mass ratio of 2:1. All films exhibited good antioxidant properties and significantly delayed oil deterioration when used for beef tallow preservation. The release behaviour of resveratrol in 95% ethanol as a food simulant was determined by film composition. The fabricated films exhibit significant potential for beef tallow preservation applications. Furthermore, LMP can improve the stability of resveratrol-FG complexes and compete with resveratrol for binding FG to accelerate resveratrol release.

Engineered bone tissues using biomineralized gelatin methacryloyl/sodium alginate hydrogels

At present, the treatment of bone defect is one of the most concerned problems in biomedical fields. Despite the wide variety of scaffolds, there is a challenge to select materials that can mimic the structural integrity and biocompatibility of natural bone. In our study, gelatin methacryloyl (GelMA) and sodium alginate (Alg) were used to prepare three-dimensional (3D) GelMA/Alg hybrid hydrogel, which can simulate the structure and biological function of natural extracellular matrix due to their high water content and porous structure. The interconnected and homogeneous pores of the scaffold facilitate the transport of nutrients during the bone regeneration. Then hydroxyapatite (HA) coated GelMA/Alg (GelMA/Alg-HA) hydrogel was obtained by sequential mineralization. The mineralized hydrogel was obtained by immersing hydrogel alternately in a solution of calcium and phosphorus at 37 °C. The hydrogel was modified with a coating of HA under a mild condition. The calcium crosslinked Alg could provide nucleation sites for HA crystals. And the sequential mineralization will improve the physical properties and osteoinductivity of the hydrogels by introducing HA, which is similar to the mineral component of natural bone. Analytical results confirmed that the HA particles were uniformly distributed in the surface of the hydrogels and the mineral contents were about 40% after three cycles. The compressive strength was improved from 22.43 ± 6.39 to 131.03 ± 9.26 kPa. In addition, MC3T3-E1 cell co-culture experiments shown that the mineralized GelMA/Alg-HA hybrid hydrogel possess good biocompatibility, which is conducive to the growth of new bone tissue and bone repair.

Kappa-carrageenan enhances the gelation and structural changes of egg yolk via electrostatic interactions with yolk protein

The effect of κ-carrageenan (κ-C) on yolk over heat-induced gelation at natural yolk pH (6.2) and natural whole egg pH (7.5) was studied. The results showed the zeta potential values changed from -2.3 to -31.3 mV, from -8.6 to -28.6 mV for native pH yolk and pH 7.5 yolk because of the κ-C addition, respectively. These results indicated electrostatic interactions formed between protein and κ-C. The average area of holes formed by yolk gelation increased by κ-C addition. The addition of 1.0% κ-C decreased the gelling points from 62.1 to 54.4 °C, from 64.5 to 61. 6 °C for native pH and pH 7.5 yolk, respectively. A schematic model was established to show that κ-C enhances the yolk properties via electrostatic interactions. And the Fourier transform infrared (FTIR) spectroscopy verified the formation of κ-C-protein interactions. This study provides a guidance for designing novel food systems containing yolk and κ-C.

Rheological Properties of Fish Gelatin Modified with Sodium Alginate

Polyelectrolyte complexes of sodium alginate and gelatin obtained from cold-blooded fish were studied for potential application as structure-forming agents in food hydrogels. The mass ratio of sodium alginate to gelatin plays a decisive role in the sol-gel transition and rheological behavior of the complexes. Differences in the sol-gel transition temperature were observed upon heating and cooling, as is typical for such materials. We investigated the characteristics of this transition by measuring the isothermal changes in the elastic modulus over time at a constant frequency and the transition temperature at a range of frequencies. The kinetic nature of this transition depends on the composition of the complexes. A characteristic alginate-gelatin mass ratio is the ratio at which maximum transition temperature as well as elastic modulus and viscosity (rheological parameters) values are obtained; the characteristic mass ratio for these complexes was found to be 0.06. Calculation of the ionic group ratios in the biopolymers that form complexes and comparison of these data with the turbidimetric titration results clarified the origin of these maxima. Measuring the viscoelastic properties and the creep-elastic recoil of the samples allowed us to characterize these materials as viscoelastic media with a viscosity in the order of 103-104 Pa·s and an elastic modulus in the order of 102-103 Pa. These values drastically decrease at a certain stress threshold, which can be treated as the gel strength limit. Therefore, the observed rheological behavior of gels formed by fish gelatin modified with sodium alginate characterizes them as typical viscoelastic soft matter.

Modified Fish Gelatin as an Alternative to Mammalian Gelatin in Modern Food Technologies

This review considers the main properties of fish gelatin that determine its use in food technologies. A comparative analysis of the amino acid composition of gelatin from cold-water and warm-water fish species, in comparison with gelatin from mammals, which is traditionally used in the food industry, is presented. Fish gelatin is characterized by a reduced content of proline and hydroxyproline which are responsible for the formation of collagen-like triple helices. For this reason, fish gelatin gels are less durable and have lower gelation and melting temperatures than mammalian gelatin. These properties impose significant restrictions on the use of fish gelatin in the technology of gelled food as an alternative to porcine and bovine gelatin. This problem can be solved by modifying the functional characteristics of fish gelatin by adding natural ionic polysaccharides, which, under certain conditions, are capable of forming polyelectrolyte complexes with gelatin, creating additional nodes in the spatial network of the gel.

The interaction between sodium alginate and myofibrillar proteins: The rheological and emulsifying properties of their mixture

The interaction between sodium alginate (SA) and turbot myofibrillar proteins (TMP) and the effects of SA concentration (0.1%-0.5%) on the rheological and emulsifying properties of the mixture at neutral pH were investigated. TMP and SA formed complexes through electrostatic repulsion and hydrophobic interaction. The FT-IR analysis indicated that hydrogen bonding was also related to the interaction. With the addition of SA, the electrostatic repulsion between molecules enhanced, which prevented protein aggregation and improved the stability of dispersions. The TMP/SA mixture showed non-Newtonian shear-thinning behavior. The viscosity gradually increased with the increasing SA concentration. TMP and SA formed an interconnected gel-like network structure with a predominant elastic behavior. The strength of network increased due to the strong repulsion between the two biopolymers. Both EAI and ESI of TMP significantly increased after SA addition. The addition of SA reduced droplet size of emulsions. The emulsions also showed pseudoplastic behavior. Addition of SA increased stability of emulsions by increasing viscosity of continuous phase. Complexation with SA effectively improved the rheological and emulsifying properties of fish myofibrillar proteins. These results contributed to the efficient utilization of marine fish proteins as functional ingredients in food products.

Bromelain Kinetics and Mechanism on Myofibril from Golden Pomfret (Trachinotus blochii)

Bromelain was used to tenderize golden pomfrets (Trachinotus blochii). The enzyme kinetic model was x=2.447×ln[1+(1332.21×E0S0-1.74)t], which indicated that the degree of hydrolysis (DH, x) was dependent on hydrolysis time (t), the initial concentration of myofibril (S₀ ) and bromelain (E₀ ). The relationship between the overall hydrolysis rate (v), S₀ , E₀ , and t is demonstrated as: v=(16.50(E0S0)-1.33)S0 exp {-2.447ln[1+(1332.21E0S0-1.74)t2]}. Sample of 0.40% E₀ /S₀ was further used to study the effects of hydrolysis time on the changes of proteins, peptides, free amino acids (FAA), and protein nanostructure. SDS-PAGE result showed that myosin heavy chain was degraded dramatically from 22.88% before treatment to 12.03% after 2 min bromelain treatment. Meanwhile, bromelain did not exhibit activity towards actin, trypomyosin, myosin light chain, and troponin C. A general increase of amino acids indicated the increased DH and the preferential cleavage sites of bromelain in the descending order of lysine, glutamic acid, glycine, ornithine, methionine sulfoxide, and alanine. Atomic force microscope images showed that the strip-like structure of myofibril was considerably degraded by bromelain, and the granulation of protein after 20 min indicated possible self-assembling of protein hydrolysate. Confocal laser scanning microscopy further confirmed the degradation of myofibril proteins and formation of protein aggregates.

PRACTICAL APPLICATION

Meat of golden pomfrets is tough, thus not idea for fish balls or fish cakes. Tenderization is essential to achieve desired texture and consumer acceptance, especially for this fish meat with intrinsic hard texture. Bromelain can be extracted from pineapple processing waste. Enzymatic kinetics was studied to instruct industry to control the tenderness of the processed fish meat. The microstructural and mechanism study elucidate the process, thus could be applied to improve the quality of the seafood products correspondingly.

Structural Modification of Fish Gelatin by the Addition of Gellan, κ-Carrageenan, and Salts Mimics the Critical Physicochemical Properties of Pork Gelatin

Pork gelatin is not suitable for halal and kosher application; however, fish gelatin (FG) can be modified for use as a pork gelatin (PG) mimetic. Herein, low-acyl gellan (GE), κ-carrageenan (KC), and salts (CaCl₂ or KCl) were combined with a 180 Bloom tilapia FG. A formulation comprising 5.925% (w/v) FG + 0.025% (w/v) GE + 3mM CaCl₂ best matched the physicochemical properties of PG. The modification increased the FG gel strength from 115 ± 2 to 149 ± 2 g (matching the 148 ± 2 of PG), while the T_m increased from 27.9 ± 1.0 to 32.4 ± 0.8 °C (matching the 33.1 ± 0.3 °C of PG). Nanoaggregates (diameter between 150 and 300 nm) could be an important structural factor affecting the physicochemical properties, as both PG and GE-modified FG showed a similar frequency distribution in this size group (57.4 ± 1.6% (PG) compared with 56.3 ± 2.2% (modified FG)). To further explore the differences between KC and GE in modifying of FG's structure, the FG-KC and FG-GE gels were compared. The zeta potential and Fourier transform infrared (FTIR) spectroscopy results for the FG-KC gel supported an associative interaction with complex formation, as indicated from the large aggregates and amorphous phase under atomic force microscopy (AFM). Contrastingly, a segregative FG-GE interaction took place in presence of CaCl₂ . These structures and interaction differences between FG-GE and FG-KC influenced the macro-properties of FG, possibly explaining the differences in the modification of the melting temperature of FG. A diagram representing the interaction-structure-physicochemical properties was proposed to explain the differences between the FG-GE and FG-KC gels.

PRACTICAL APPLICATION

Certain people cannot consume any pork product or derivatives for religious reasons, thus it is essential to find a pork gelatin (PG) substitute for food product development. The commonly used polysaccharides, gellan and carrageenan, together with salt, can be added to fish gelatin (FG) to match the textural properties of PG, representing a promising substitute for PG. The difference in the mechanism of gellan and carrageenan to improve properties of FG has been revealed from nanostructure level. The use of food grade ingredients and simple mixing process are favorable in the food industry.

Gelation kinetics and characterization of enzymatically enhanced fish scale gelatin-pectin coacervate

BACKGROUND

Protein-polysaccharide complex coacervations have been considered extensively for the development of functional foods. The main problem of the complex coacervates is that they are highly unstable under different conditions and that cross-linking is necessary to stabilize them. In this study, the effects of pectin at different concentrations on the gel and structural properties of fish scale gelatin (FSG)-high methoxyl citrus pectin (HMP) coacervate enhanced by microbial transglutaminase (MTGase) were studied.

RESULTS

The gelation rates and gel strength of the MTGase-enhanced FSG-HMP coacervate gels decreased with increasing HMP concentration. However, the enhanced coacervate gels exhibited better thermal behavior and mechanical properties compared with the original gels. Also, TG-P₈ exhibited the highest melting point (27.15 ± 0.12 °C), gelation point (15.65 ± 0.01 °C) and stress (15.36 ± 0.48 kPa) as HMP was 8 g kg^-1 . Particle size distribution, fluorescence emission and UV absorbance spectra indicated that MTGase and HMP could make FSG form large aggregates. Moreover, confocal laser scanning microscopy of treated coacervate gels showed a continuous protein phase at low HMP concentrations.

CONCLUSION

FSG and HMP could form soluble coacervate, and MTGase could improve the thermal and mechanical properties of coacervate gels. © 2017 Society of Chemical Industry.

Deciphering the interactions of fish gelatine and hyaluronic acid in aqueous solutions

The interactions of fish gelatine (FG) with hyaluronic acid (HA) are studied in an aqueous environment at 25°C by turbidimetric titration, confocal scanning laser microscopy, dynamic light scattering, zeta potentiometry, spectrophotometry with methylene blue, and construction of state diagrams. FG forms soluble complexes with HA above a boundary pH (pH_φ1), where both biopolymers are net-negatively charged, but develop insoluble complexes as liquid-state complex coacervates below pH_φ1, where the two biopolymers are oppositely charged. The insoluble complexes are continuously aggregated with further acid titration, followed by immediate visible phase-separation when another boundary pH (pH_p) is reached. The complex formation is mainly driven by electrostatic attractions rather than hydrogen bonding or hydrophobic interactions. The complex formation is promoted by increasing FG-to-HA weight ratio or total biopolymer concentration, or at a low ionic strength, but significantly suppressed in the presence of high ionic strength.