Complexation of κ-carrageenan with gelatin in the aqueous phase analysed by 1H NMR kinetics and relaxation

Development and characterization of semi-refined iota carrageenan/fish gelatin-based biocomposite film incorporated with SiO2/ZnO nanoparticles

Food packaging based on natural polymers from polysaccharides and proteins can be an alternative to replace conventional plastics. In the present study, semi-refined iota carrageenan (SRIC) and fish gelatin (FG) were used as polymer matrix film with different concentration ratios (0.5:1.5 %, 1.0:1.0 % and 1.5:0.5 % w/w) and SiO2-ZnO nanoparticles were incorporated as fillers with the same concentration in all formulas (0.5:1.5 % w/w carrageenan-fish gelatin). This study aimed to develop films for food packaging applications with desirable physical, mechanical, optical, chemical, and microbiological properties. The results showed that incorporating SiO2-ZnO nanoparticles significantly (p < 0.05) improved the films' elongation at break, UV-screening properties, and antimicrobial activity. Also, the films' thickness, degradability, and transparency significantly (p < 0.05) increased with the higher concentration of fish gelatin addition in the SRIC matrix polymer. The best formula was obtained on the SRIC-FG film at the ratio of 1.5:0.5 % w/w, which performed excellent antimicrobial activity. Thus, semi-refined iota carrageenan/fish gelatin-based biocomposite film incorporated with SiO2-ZnO nanoparticles can be potentially developed as eco-friendly and intelligent food packaging materials to resolve traditional plastic-related issues and prevent food waste.

Gelatine Blends Modified with Polysaccharides: A Potential Alternative to Non-Degradable Plastics

Non-degradable plastics of petrochemical origin are a contemporary problem of society. Due to the large amount of plastic waste, there are problems with their disposal or storage, where the most common types of plastic waste are disposable tableware, bags, packaging, bottles, and containers, and not all of them can be recycled. Due to growing ecological awareness, interest in the topics of biodegradable materials suitable for disposable items has begun to reduce the consumption of non-degradable plastics. An example of such materials are biodegradable biopolymers and their derivatives, which can be used to create the so-called bioplastics and biopolymer blends. In this article, gelatine blends modified with polysaccharides (e.g., agarose or carrageenan) were created and tested in order to obtain a stable biopolymer coating. Various techniques were used to characterize the resulting bioplastics, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), contact angle measurements, and surface energy characterization. The influence of thermal and microbiological degradation on the properties of the blends was also investigated. From the analysis, it can be observed that the addition of agarose increased the hardness of the mixture by 27% compared to the control sample without the addition of polysaccharides. In addition, there was an increase in the surface energy (24%), softening point (15%), and glass transition temperature (14%) compared to the control sample. The addition of starch to the gelatine matrix increased the softening point by 15% and the glass transition temperature by 6%. After aging, both compounds showed an increase in hardness of 26% and a decrease in tensile strength of 60%. This offers an opportunity as application materials in the form of biopolymer coatings, dietary supplements, skin care products, short-term and single-contact decorative elements, food, medical, floriculture, and decorative industries.

Effect of protein-polysaccharide hybrid gelator system on the material properties and 3D extrusion printability of mashed potatoes

Mashed potatoes (MP) are famous as ready-to-eat products due to their excellent taste and texture. Problems such as complex injection occur when MP is used as a 3D printing material. To improve the smoothness of MP loading into a 3D syringe barrel and its 3D extrusion printability, the effects of the protein-polysaccharide hybrid gelator developed with different gelatin-B (GB, 2%, 4%, 6%) and κ-carrageenan (KG, 1%) on the rheology and 3D extrusion printability of MP were studied. The rheological results showed that the MP developed a glass transition temperature by adding the hybrid gelator. Adding 1% KG+6% GB (w/w, dry base) to the hybrid gelator has good shear thinning and self-supporting properties and showed the best geometric accuracy. In the extrusion stage, the yield stress, the consistency index (K), and the flow behavior index (n) of MP were 470.69 Pa, 313.48 Pa·sn, and 0.159, respectively. In the recovery stage, the shear recovery time is 30 s. In the self-supporting stage, the storage modulus and loss modulus are significantly higher than those of other groups and have the strongest mechanical properties. Moreover, water distribution, Fourier transform infrared spectroscopy, X-ray diffraction analysis, and microstructure of printed MP with different hybrid gelators were observed. The addition of hybrid gelators reduced the content of free water in MP. Hybrid gelators did not produce new functional groups in the printed materials and did not change the structure of starch. These results provide new insights for applying protein and polysaccharide hybrid gelators in 3D printing.

Synergistic adsorption of methylene blue with carrageenan/hydrochar-derived activated carbon hydrogel composites: Insights and optimization strategies

The study explores the use of hydrochar-derived activated carbon (AC) to improve the adsorption capacity and mechanical properties of carrageenan (CAR) hydrogel beads. Four distinct samples, with carrageenan to activated carbon ratios of 1:0 (CAR), 2:1 (CAC2), 4:1 (CAC4), and 10:1 (CAC10), were prepared. These polymeric beads underwent comprehensive evaluation for their methylene blue (MB) adsorption capacity, gel content (GC), and swelling ratio (SR). Increasing activated carbon content up to 50 % of carrageenan mass significantly enhanced GC and SR by 20.57 % and 429.24 %, respectively. Various analytical techniques were employed to characterize the composites, including FTIR, XRD, Raman Spectroscopy, BET, SEM, and EDS-Mapping. Batch adsorption tests investigated the effects of pH, contact time, dye concentration, and temperature on MB adsorption. Maximum adsorption capacities for CAR, CAC10, CAC4, and CAC2 were 475.48, 558.54, 635.93, and 552.35 mg/g, respectively, under optimal conditions. Kinetic models (Elovich and pseudo-second-order) and isotherm models (Temkin for CAR and Freundlich for CAC10, CAC4, and CAC2) fitted well with the experimental data. Thermodynamic analysis showed spontaneous, exothermic MB adsorption. Primary mechanisms include electrostatic attraction, hydrogen bonding, n-π, and π-π stacking. The study highlights enhanced adsorption capacity of carrageenan hydrogel via carrageenan/activated carbon composites, providing cost-effective wastewater treatment.

Polysaccharide-coated quercetin-loaded nanoliposomes mitigate bitterness: A comparison of carrageenan, pectin, and trehalose

The intense bitterness of quercetin poses a challenge to its utilization in the food industry. To address this issue, three anionic polysaccharides (carrageenan, pectin, and trehalose) were individually incorporated to fabricate polysaccharide-coated liposome nanocarriers. Electronic tongue analysis revealed a significant decreasing bitterness value (10.34 ± 0.07 mV, sensory score 1.8 ± 0.2, taste weak bitter) in quercetin-loaded nanoliposomes, compared with the bitterness value of quercetin aqueous solution (14 ± 0.01 mV, sensory score 7.3 ± 0.3, taste strong bitter). Furthermore, the polysaccharide-coated nanoliposomes exhibited an even greater capacity to mask the bitterness of quercetin, with carrageenan coated nanoliposomes demonstrating the most pronounced effect. The superior bitter masking ability of carrageenan coated nanoliposomes can be attributed to its high charge and viscosity. In sensory evaluations, gummy incorporated with carrageenan-coated nanoliposomes received the highest ratings, exhibiting enhanced overall palatability and antioxidant activity. This study offers insights into expanding the use of bitter nutrients in food applications and paves the way for more appealing and healthful food products.

Helicity degree of carrageenan conformation determines the polysaccharide and water interactions

The polysaccharide in solution at critical concentration, Cc (g/L), is assimilated to a nano hydrogel (nHG) made of a single polysaccharide chain. Taking as reference the characteristic temperature of 20 ± 2 °C at which kappa-carrageenan (κ-Car) nHG swelling is greater with a Cc = 0.55 ± 0.05 g/L, the temperature of the minimum deswelling in the presence of KCl was found at 30 ± 2 °C for 5 mM with a Cc = 1.15 ± 0.05 g/L but not measurable above 100 °C for 10 mM of which Cc = 1.3 ± 0.05 g/L. Lowering the temperature to 5 °C, contraction of the nHG and further coil-helix transition with self-assembly increases the sample's viscosity, which steadily evolves with time in a logarithmic scale. Accordingly, the relative increment of the viscosity per unit of concentration, R_v (L/g), should increase in agreement with increasing polysaccharide concentration. But the R_v decreases for κ-Car samples above 3.5 ± 0.5 g/L in the presence of 10 mM KCl under steady shear 15 s^-1. This reflects a decrease of κ-Car helicity degree knowing that the polysaccharide is rather hydrophilic when its helicity degree is the lowest.

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.

Ultrasonic-assisted glycosylation with κ-carrageenan on the functional and structural properties of fish gelatin

BACKGROUND

Fish gelatin (FG) has multifunctional properties similar to mammalian gelatin (MG), and it has been recognized as the optimal alternative to MG. While its poor surface-active and gelling properties significantly limit its application values, glycosylation has been successfully used to increase surface-active properties of FG, but the influence of ultrasonic-associated glycosylation (UAG) on the gelling and structural characteristics of FG is still rarely reported. This article explores UAG (100-200 W, 0.5-1 h) with κ-carrageenan (κC) on the functional properties (emulsifying, gelling and rheological properties) and structural characteristics of FG.

RESULTS

The longer time and higher power of ultrasonics accelerated the glycosylation reaction with an increase in glycosylation degree and browning index values. Compared with original FG, FG-κC mixture and bovine gelatin, UAG-modified FG possessed higher emulsification activity index, emulsion stability index, gel strength, hardness and melting temperature values. Among them, gelatin modified by appropriate ultrasonic conditions (200 W, 0.5 h) had the highest emulsifying and gelling properties. Rheological results showed that UAG contributed to the gelation process of gelatin with advanced gelation time and endowed it with high viscosity. Structural analysis indicated that UAG promoted κC to link with FG by the formation of covalent and hydrogen bonds, restricting more bound and immobilized water in the gels, exhibiting higher gelling properties.

CONCLUSION

This work showed that UAG with κC is a promising method to produce high gelling and emulsifying properties of FG that could replace MG. © 2023 Society of Chemical Industry.

Double-Reinforced Fish Gelatin Composite Scaffolds for Osteochondral Substitutes

Genipin crosslinked composite blends of fish gelatin/kappa-carrageenan (fG/κC) with different concentrations of graphene oxide (GO) for osteochondral substitutes were prepared by a simple solution-blending method. The resulting structures were examined by micro-computer tomography, swelling studies, enzymatic degradations, compressions tests, MTT, LDH, and LIVE/DEAD assays. The derived findings revealed that genipin crosslinked fG/κC blends reinforced with GO have a homogenous morphology with ideal pore dimensions of 200-500 µm for bones alternative. GO additivation with a concentration above 1.25% increased the blends' fluid absorption. The full degradation of the blends occurs in 10 days and the gel fraction stability increases with GO concentration. The blend compression modules decrease at first until fG/κC GO3, which has the least elastic behavior, then by raising the GO concentration the blends start to regain elasticity. The MC3T3-E1 cell viability reveals less viable cells with the increase of GO concentration. The LDH together with the LIVE/DEAD assays reports a high concentration of live and healthy cells in all types of composite blends and very few dead cells at the higher GO content.

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.

Modulation of Molecular Structure and Mechanical Properties of κ-Carrageenan-Gelatin Hydrogel with Multi-Walled Carbon Nanotubes

Hydrogels, three-dimensional hydrophilic water-insoluble polymer networks having mechanical properties inherent for solids, have attracted continuous research attention over a long time period. Here, we studied the structure and properties of hydrogel based on gelatin, κ-carrageenan and CNTs using the combination of SAXS, PXRD, AFM microscopy, SEM and rheology methods. We have shown that the integration of polysaccharide and protein in the composite hydrogel leads to suppression of their individual structural features and homogenization of two macromolecular components into a single structural formation. According to obtained SAXS results, we observed the supramolecular complex, which includes both polysaccharide and protein components associated with each other. It was determined that hydrogel structure formed in the initial solution state (dispersion) retains hydrogel supramolecular structure under its cooling up to gel state. The sizes of dense cores of these polyelectrolyte complexes (PEC) slightly decrease in the gel state in comparison with PEC water dispersion. The introduction of CNTs to hydrogel does not principally change the type of supramolecular structure and common structural tendencies observed for dispersion and gel states of the system. It was shown that carbon nanotubes embedded in hydrogel act as the supplementary template for formation of the three-dimensional net, giving additional mechanical strengthening to the studied system.

Algal Polysaccharides-Based Hydrogels: Extraction, Synthesis, Characterization, and Applications

Hydrogels are three-dimensional crosslinked hydrophilic polymer networks with great potential in drug delivery, tissue engineering, wound dressing, agrochemicals application, food packaging, and cosmetics. However, conventional synthetic polymer hydrogels may be hazardous and have poor biocompatibility and biodegradability. Algal polysaccharides are abundant natural products with biocompatible and biodegradable properties. Polysaccharides and their derivatives also possess unique features such as physicochemical properties, hydrophilicity, mechanical strength, and tunable functionality. As such, algal polysaccharides have been widely exploited as building blocks in the fabrication of polysaccharide-based hydrogels through physical and/or chemical crosslinking. In this review, we discuss the extraction and characterization of polysaccharides derived from algae. This review focuses on recent advances in synthesis and applications of algal polysaccharides-based hydrogels. Additionally, we discuss the techno-economic analyses of chitosan and acrylic acid-based hydrogels, drawing attention to the importance of such analyses for hydrogels. Finally, the future prospects of algal polysaccharides-based hydrogels are outlined.

Strong fish gelatin hydrogels double crosslinked by transglutaminase and carrageenan

Gelatin hydrogels are usually soft and thermally unstable. Here, strong fish gelatin hydrogels were successfully prepared by double crosslinking gelatin with transglutaminase (TGase) and κ-carrageenan, and the mechanical properties and thermal stability of the double crosslinked gelatin hydrogels were significantly improved. Results showed that the gel strength, compression fracture stress and storage modulus of the double crosslinked gelatin hydrogels all reached the largest value when the concentration of TGase was 20 U/g gelatin. The double crosslinked gelatin hydrogels were also thermally stable due to the existence of the covalent crosslinks. The effect of TGase concentration on the physical properties and microstructure of the double crosslinked hydrogels were analyzed, and the differences between double crosslinked gelatin hydrogels and gelatin hydrogels single crosslinked by TGase or carrageenan were also systematically compared. This article is of great significance for expanding the application of natural polymer-based hydrogels.

Morphology-controllable amphiphilic cellulose microgels made from self-assembly of hydrophobic long-chain bromide-alkylated-cellulose/gelatin copolymer

A cellulose-based microgel is firstly synthesized via chemically coupling gelatin and cellulose, and then amphiphilic cellulose copolymers (HMGC) are prepared by alkylated cellulose-based microgel from different long-chain alkyl groups. The long-chain alkyl group is mainly bonded onto the residual hydroxyl group at C₆ from the AGU of cellulose and the imino groups of gelatin, respectively. The results of self-assembly behavior of HMGC demonstrate that the critical aggregation concentrations of the microgels are in the range from 0.628 to 0.075 mg/mL, and the corresponding hydrodynamic diameters are between 104-1000 nm. Besides, the HMGC can self-assemble into microgels of various morphologies including cotton flocculence, sphere, rod-like, vesicle, flower-like cluster, snowflake-like, urchin-like, and coral shapes. These novel morphologies can be controlled by adjusting the degree of alkylation, the length of the alkyl chain, and the concentration of microgel. Furthermore, the possible formation mechanism of the multiform microgels is proposed from the chain conformation.

Recovery of Gelatin from Bovine Skin with the Aid of Pepsin and Its Effects on the Characteristics of the Extracted Gelatin

Pepsin enzyme was used to pretreat the bovine skin at the rate of 5, 15, and 25 units of enzyme/g of skin to recover gelatin, and the recovered gelatins were referred to as Pe5, Pe15, and Pe25, respectively. The gelatin yield increased significantly (p < 0.05) from 18.17% for Pe5 to 24.67% for Pe25 as the level of pepsin increased, but the corresponding gel strength and viscosity decreased significantly (p < 0.05) from 215.49 to 56.06 g and 9.17 to 8.17 mPa·s for Pe5 and Pe25, respectively. β- and α1- and α2-chains were degraded entirely in all the gelatins samples as observed in protein pattern elaborated by gel electrophoresis. ¹H nuclear magnetic resonance (¹H NMR) analysis indicated the coiled structure of gelatin protein chains. The lowest amide III amplitude of Pe25 as found by Fourier transform infrared (FTIR) spectroscopy indicated that α-helix structure of protein chains were lost to more irregular coiled structure. Thus, it could be summarized that pepsin might be used at the lower level (5 units/g of wet skin) to extract gelatin from bovine skin with good functional properties and at higher level (15/25 units/g of wet skin) to obtain gelatin of industrial grade with high yield.

Textural and structural properties of a κ-carrageenan-konjac gum mixed gel: effects of κ-carrageenan concentration, mixing ratio, sucrose and Ca2+ concentrations and its application in milk pudding

BACKGROUND

Mixtures of carrageenan and konjac gum are useful for specific applications in gel-based foods. Focusing on the changes of textural and structural properties, the effects of κ-carrageenan and konjac ratio and sucrose and Ca²⁺ concentrations on mixed gels were studied in this research. Furthermore, application of κ-carrageenan-konjac gum mixed gel to milk puddings was investigated.

RESULTS

There was a better synergistic effect when the ratio of κ-carrageenan and konjac was 7:3. The mixed gel containing 10 g kg^-1 κ-carrageenan-konjac gum was characterized by higher hardness, chewiness, adhesiveness and resilience and denser network structure. Besides, the addition of 5-10 wt% sucrose or 0.02 wt% Ca²⁺ could enhance the hardness, chewiness and adhesiveness of the mixed gel, as well as affording a denser network structure. For milk pudding, moderate hardness, chewiness and resilience could be obtained by adding 1.5 g kg^-1 κ-carrageenan-konjac gum mixture.

CONCLUSIONS

This research provides useful information for the formation of κ-carrageenan-konjac gum gel and its application in milk pudding. © 2020 Society of Chemical Industry.

Studying the "Rigid-Flexible" Properties of Polymeric Micelle Core-Forming Segments with a Hydrophobic Phthalocyanine Probe Using NMR and UV Spectroscopy

The aim of the performed studies was to thoroughly examine the internal structure of self-assembled nanocarriers (i.e., polymeric micelles-PMs) by means of a hydrophobic phthalocyanine probe in order to identify the crucial features that are required to enhance the photoactive probe stability and reactivity. PMs of hydrophilic poly(ethylene glycol) and hydrophobic poly(ε-caprolactone) (PCL) or poly(d,l-lactide) (PDLLA) were fabricated and loaded with tetra tert-butyl zinc(II) phthalocyanine (ZnPc-t-but₄), a multifunctional spectroscopic probe with a profound ability to generate singlet oxygen upon irradiation. The presence of subdomains, comprising "rigid" and "flexible" regions, in the studied block copolymers' micelles as well as their interactions with the probe molecules, were assessed by various high-resolution NMR measurements [e.g., through-space magnetic interactions by the 1D NOE effect, pulsed field gradient spin-echo, and spin-lattice relaxation time (T₁) techniques]. The studies of the impact of the core-type microenvironment on the ZnPc-t-but₄ photochemical performance also included photobleaching and reactive oxygen species measurements. ZnPc-t-but₄ molecules were found to exhibit spatial proximity effects with both (PCL and PDLLA) hydrophobic polymer chains and interact with both subdomains, which are characterized by different rigidities. It was deduced that the interfaces between particular subdomains constitute an optimal host space for probe molecules, especially in the context of photochemical stability, photoactivity (i.e., for significant enhancement of singlet oxygen generation rates), and aggregation prevention. The present contribution proves that the combination of an appropriate probe, high-resolution NMR techniques, and UV-vis spectroscopy enables one to gain complex information about the subtle structure of PMs essential for their application as nanocarriers for photoactive compounds, for example, in photodynamic therapy, nanotheranostics, combination therapy, or photocatalysis, where the micelles constitute the optimal microenvironment for the desired photoreactions.

A review of NMR analysis in polysaccharide structure and conformation: Progress, challenge and perspective

Nuclear magnetic resonance (NMR) has been widely used as an analytical chemistry technique to investigate the molecular structure and conformation of polysaccharides. Combined with 1D spectra, chemical shifts and coupling constants in both homo- and heteronuclear 2D NMR spectra are able to infer the linkage and sequence of sugar residues. Besides, NMR has also been applied in conformation, quantitative analysis, cell wall in situ, degradation, polysaccharide mixture interaction analysis, as well as carbohydrates impurities profiling. This review summarizes the principle and development of NMR in polysaccharides analysis, and provides NMR spectra data collections of some common polysaccharides. It will help to promote the application of NMR in complex polysaccharides of biochemical interest, and provide valuable information on commercial polysaccharide products.

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.

Microwave-initiated rapid synthesis of phthalated cashew gum for drug delivery systems

Chemical modification of polysaccharides is an important approach for their transformation into customized matrices that suit different applications. Microwave irradiation (MW) has been used to catalyze chemical reactions. This study developed a method of MW-initiated synthesis for the production of phthalated cashew gum (Phat-CG). The structural characteristics and physicochemical properties of the modified biopolymers were investigated by FTIR, GPC, ¹H NMR, relaxometry, elemental analysis, thermal analysis, XRD, degree of substitution, and solubility. Phat-CG was used as a matrix for drug delivery systems using benznidazole (BNZ) as a model drug. BNZ is used in the pharmacotherapy of Chagas disease. The nanoparticles were characterized by size, PDI, zeta potential, AFM, and in vitro release. The nanoparticles had a size of 288.8 nm, PDI of 0.27, and zeta potential of -31.8 mV. The results showed that Phat-CG has interesting and promising properties as a new alternative for improving the treatment of Chagas disease.

High-strength carrageenan fibers with compactly packed chain structure induced by combination of Ba2+ and ethanol

Carrageenan fibers have attractive applications in textile, but their low strength remains a problem that needs to be urgently addressed. In this work, a novel facile, environmental friendly method for fabricate high-strength carrageenan fibers is proposed. It involves the crosslinking of a small amount of Ba²⁺ ions in the carrageenan solution, followed by using recyclable alcohol in coagulation and stretching baths. Carrageenan molecular chains were allowed to first sufficiently interact with metal barium ions, and then were stretched and dehydrated with alcohol to increase the hydrogen bonding interaction between the molecular chains. As a result, the carrageenan fibers with high-strength ionic and hydrogen bonds were obtained. The fibers obtained by the novel method had high tensile strength at 1.63 cN/dtex, which is two times higher than that of those obtained by the traditional process.

Angelica Essential Oil Loaded Electrospun Gelatin Nanofibers for Active Food Packaging Application

The development of food packaging possessing bioactivities which could extend the shelf life of food has gained increased interest in recent years. In this study, gelatin nanofibers with encapsulated angelica essential oil (AEO) were fabricated via electrospinning. The morphology of gelatin/AEO nanofibers was examined by scanning electron microscopy (SEM) and the addition of AEO resulted in the increase of fiber diameter. The proton nuclear magnetic resonance (1H-NMR) spectra were measured to confirm the presence of AEO in nanofibers. The hydrophobic property of gelatin nanofibers was also found to be improved with the addition of AEO. The nanofibers incorporated with AEO showed significant antioxidant activity and inhibitory effect against both Gram-negative and Gram-positive bacteria in a concentration dependent manner. Furthermore, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay demonstrated that the developed gelatin/AEO nanofibers revealed no cytotoxicity effect. Thus, gelatin nanofibers incorporated with AEO can be used as potential food packaging.

κ-Carrageenan/Sodium alginate double-network hydrogel with enhanced mechanical properties, anti-swelling, and adsorption capacity

The abuse of antibiotics is becoming increasingly serious, particularly in offshore aquaculture areas. Double-network polymer gel has good prospects for environmental application for the removal of antibiotics. In this work, κ-Carrageenan/Sodium Alginate (κ-car/SA) double-network hydrogels were designed and synthesized with enhanced mechanical properties, anti-swelling, and adsorption capacity. It was found that the intermolecular interaction and viscosity tend to increase with the increasing concentration of κ-carrageenan. The swelling degree of the composite hydrogel in NaCl solution presented a decreasing trend with the increase of carrageenan. SA can effectively improve the mechanical properties of κ-carrageenan composite gel and enhance its compressive resistance and elasticity. Ciprofloxacin (CIP) was used as the model pollutant for testing the adsorption performance. The results show that the Langmuir-Freundlich isotherm model is more suitable for fitting the adsorption isotherm data of CIP on gel beads, which indicates that κ-car/SA hydrogels have heterogeneous surface and different binding sites. κ-car/SA composite double-network hydrogels exhibit excellent adsorption properties for CIP (229 mg/g). The optimal adsorption capacity of κ-car/SA composite hydrogels was obtained at pH 4, and the adsorption capacity of the hydrogels increased with increasing ion concentration. FTIR spectroscopy and the Zeta potential test analyses showed that the adsorption mechanism may be explained by hydrogen bonding and the electrostatic interactions between κ-car/SA composite hydrogels and CIP. The formation of the new double-network hydrogel provided good properties and development potential for the adsorption of antibiotic in water.

Self-assembled gelatin-ι-carrageenan encapsulation structures for intestinal-targeted release applications

In this work, natural biopolymeric encapsulation structures were developed through the self-assembly of gelatin and ι-carrageenan in aqueous solutions. The interactions of this binary system and of a ternary system containing a polyphenol-rich extract were deeply explored for the development of intestinal delivery systems. The processing of the structures (extrusion vs. freeze-drying) greatly influenced release properties, explained by the specific interactions between gelatin and polyphenols, thus allowing for tuning the processing conditions depending on the desired target application. Release was further controlled by incorporating a divalent salt, giving raise to extract-loaded ι-carrageenan/gelatin capsules with adequate release profiles for intestinal targeted delivery. These results demonstrate the potential of exploiting biopolymer interactions for designing bioactive delivery systems using environmentally friendly processes which do not involve the use of toxic or harsh solvents or cross-linkers.