The synergistic gelation of okra polysaccharides with kappa-carrageenan and its influence on gel rheology, texture behaviour and microstructures

The texture and rheology properties of k-carrageenan and Artemisia sphaerocepdala krasch gum composite gel

This study aimed to improve the gel properties of k-carrageenan (KC). Texture analysis and dynamic rheology were used to evaluate the effects of Artemisia sphaerocepdala krasch gum (ASKG) on KC. The results indicated that ASKG formed thermo-reversible gels with enhanced properties. Rheological analysis showed that the sol-gel and gel-sol transition temperatures of the composite gel were 55.4 °C and 40.41 °C, respectively, both 6-7 °C higher than pure KC, demonstrating improved thermal stability. DSC analysis further confirmed the superior thermal stability of the composite gel, with the heat absorption peak shifting by approximately 7 °C compared to pure KC. The textural properties of pure KC showed a hardness of 225.84 g, springiness of 0.90, and gel strength of 51.87 g, while for the 7:3 KC to ASKG ratio, the hardness was 370.97 g, springiness 0.958, and gel strength 65.1 g. These values gradually decreased with increasing ASKG content. These findings suggest that intermolecular interactions between the polysaccharides improve gel stability. Additionally, the addition of low concentrations of salt ions, especially Ca2+, enhanced the texture and rheological properties. These results indicate that ASKG has significant potential to improve thermal stability and reduce brittleness in KC gels.

Curdlan inclusion modifies the rheological properties and the helix-coil transition behavior of gelatin and increases the flexibility of gelatin films

Gelatin, a natural and edible polymer, has attracted wide attention for use in food and edible packaging applications. However, its inadequate properties, especially poor flexibility, limit its broader utilization. Hybridizing different polymers is a promising strategy to achieve enhanced properties. Herein, the microstructure and characteristics of gelatin/curdlan film-forming solutions and the resulting films were systematically characterized. Effective interaction between curdlan and gelatin can be shown by a homogeneous phase morphology and increased helix-coil transition temperature. The strong interactions between gelatin and curdlan results in a well-integrated polymer network, significantly influence gelatin's properties. In particular, the samples containing higher proportion of curdlan exhibited increased elongation at break, suggesting enhanced flexibility. Overall, this research presents a promising way for improving gelatin's ductility, enhancing its potential for food-related and broader applications.

A green extraction method for agar with improved thermal stability and water holding capacity

The conventional agar extraction method has drawbacks such as high energy consumption, low yield, poor quality, and possible residual harmful factors, which greatly limit its application in high-end fields such as biomedicine and high-end materials. This work explored a new freezing-thawing-high-temperature coupling technique for agar extraction. It increased the yield and the strength of agar by 10.6 % and 13.7 %, respectively, as compared to direct high-temperature extraction of agar (HA). The greater molecular weight and lower sulfate content of agar obtained from freeze-thaw cycles combined with high temperature extraction (FA) may be attributed to the desulfurization effect caused by freeze-thaw cycles and the preservation of the molecular chain structure. The reduction in sulfate content decreases the steric hindrance resistance of the polysaccharide chains, enhances their interactions, and promotes the regularity and density of the agar structure, while also improving its water retention and thermal stability. In conclusion, this research can offer a theoretical basis and guidance for the eco-friendly extraction of agar with improved agar characteristics and expended its applications.

Removal of oxytetracycline from pharmaceutical wastewater using kappa carrageenan hydrogel

This study investigated the adsorption of Oxytetracycline (OTC) from pharmaceutical wastewater using a kappa carrageenan based hydrogel (KPB). The aim of the present study was to explore the potential of KPB for long-term pharmaceutical wastewater treatment. A sustainable adsorbent was developed to address oxytetracycline (OTC) contamination. The hydrogel's structural and adsorption characteristics were examined using various techniques like Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), X-ray powder diffraction (XRD), and kinetic models. The results revealed considerable changes in the vibrational modes and adsorption bands of the hydrogel, suggesting the effective functionalization of Bentonite nano-clay. Kappa carrageenan based hydrogel achieved the maximum removal (98.5%) of OTC at concerntration of 40 mg/L, pH 8, cotact time of 140 min and adsorbent dose of 0.1 g (KPB-3). Adsorption of OTC increased up to 99% with increasing initial concentrations. The study achieved 95% adsorption capacity for OTC using a KPB film at a concentration of 20 mg/L and a 0.1 g adsorbent dose within 60 min. It also revealed that chemisorptions processes outperform physical adsorption. The Pseudo-Second-Order model, which emphasized the importance of chemical adsorption in the removal process, is better suited to represent the adsorption behavior. Excellent matches were found that R2 = 0.99 for KPB-3, R2 = 0.984 for KPB-2 and R2 = 0.989 for KPB-1 indicated strong chemical bonding interactions. Statisctical analysis (ANOVA) was performed using SPSS (version 25) and it was found that pH and concentration had significant influence on OTC adsorption by the hydrogel, with p-values less than 0.05. The study identified that a Kappa carrageenan-based hydrogel with bentonite nano-clay and polyvinyl alcohol (PVA) can efficiently remove OTC from pharmaceutical effluent, with a p-value of 0.054, but weak positive linear associations with pH, temperature, and contact time. This research contributed to sustainable wastewater treatment and environmental engineering.

Based on hydrogen and disulfide-mediated bonds, l-lysine and l-arginine enhanced the gel properties of low-salt mixed shrimp surimi (Antarctic krill and Pacific white shrimp)

This study delved into the effects of l-lysine (Lys) and l-arginine (Arg) on the gel properties and intermolecular interactions of low-salt (NaCl, 1 g/100 g) mixed shrimp surimi (Antarctic krill and Pacific white shrimp). The addition of Lys and Arg improved the gel strength and water holding capacity of low-salt gels, which were superior to the properties of STPP and high-salt (NaCl, 2.25 g/100 g) gels. These results can be attributed to the role of Lys and Arg in enhancing hydrogen and disulfide bonds within the low-salt gel system, promoting the solubilization of myofibrillar proteins (MP) and consequently increasing the number of MP molecules participating in gel formation. Antarctic krill MP did not show gel-forming ability and exerted a diluting effect on low-salt mixed shrimp surimi gels. Molecular docking analysis indicated the stable binding of Lys and Arg to myosin.

Development of 3D printed k-carrageenan-based gummy candies modified by fenugreek gum: Correlating 3D printing performance with sol-gel transition

Temperature-responsive inks were formulated using k-carrageenan, fenugreek gum (FG), rose extracts, and sugar, of which the first two were used as the gelling agents. The interactions among components in these mixed ink formulations were investigated. Sol-gel transition and rheological properties of these inks were also correlated with extrusion, shape formation, and self (shape)-supporting aspects of 3D printing. Results indicated that incorporating FG increased inks' gelation temperature from 39.7 °C to 44.7-49.6 °C, affecting the selection of printing temperature (e.g., 0 % FG: 40 °C, 0.15 % FG: 45 °C, 0.3 % FG-0.6 % FG: 50 °C). Inks in solution states with lower viscosity (<5 Pa·s) were amenable to ensure their smooth extrusion through the tip of the printing nozzle. A shorter sol-gel transition time (approximately 100 s) during the shape formation stage facilitated the solidification of inks after extrusion. The addition of FG significantly (p<0.05) improved the mechanical properties (elastic modulus, hardness, etc.) of the printed models, which facilitated their self-supporting behavior. Low field nuclear magnetic resonance indicated that the inclusion of FG progressively restricted water mobility, consequently reducing the water syneresis rate of the mixed inks by 0.86 %-3.6 %. FG enhanced hydrogen bonding interactions among the components of these mixed inks, and helped to form a denser network.

Effect of different NaCl concentration on the structure-function relationship of citrus peel pectins modified by electrochemistry

In this study, the modified citrus peel pectins (CPPs) were successfully produced by electrochemistry with varying NaCl concentrations of 0, 0.01 % and 0.1 % w/v using an H-type cell at 40 mA current. After 4 h, the pH and oxidation-reduction potential (ORP) of oxidized CPP solution in the anodic region were 2.00- 2.52 and 371.17- 564.45 mV, respectively, due to the electrolysis of water, whereas those of reduced CPP solution in cathodic region were 9.46- 10.84 and - 202.77 ~ -230.57 mV. The modified CPPs in the anodic region (A-0, A-0.01, and A-0.1) exhibited significantly higher weight-average molecular weights and methyl esterification degrees than those in the cathodic region (C-0, C-0.01 and C-0.1). In contrast, the K⁺, Mg²⁺, and Ca²⁺ contents of A-0, A-0.01, and A-0.1 were lower than those of C-0, C-0.01 and C-0.1 due to the electrophoretic migration. Furthermore, the antioxidant activities of A-0 and A-0.01 solutions were stronger than those of the C-0, C-0.01, and C-0.1, while rheological and texture properties of their hydrogels showed contradictory results. Finally, the potential structure-function relationships of CPPs were explored by combining PCA and correlation analysis. Overall, this study introduced a potential approach for pectin purification and functional low-methoxyl pectin manufacturing.

Hydrophobic modified agar: Structural characterization and application in encapsulation and release of curcumin

In this study, three kinds of anhydrides with different structures were introduced into agar molecules to study the effects of varying degrees of substitution (DS) and anhydride structures on the physicochemical properties and curcumin (CUR) loading capacity. Increasing the carbon chain length and saturation of the anhydride affects the hydrophobic interaction and hydrogen bonding of the esterified agar, thereby changing the stable structure of the agar. Although the gel performance declined, the hydrophilic carboxyl group and the loose porous structure provide more binding sites for the adsorption of water molecules, hence providing excellent water retention (1700 %). Next, CUR was used as a hydrophobic active ingredient to study agar microspheres' drug encapsulation and in vitro release ability. Results showed that the excellent swelling and hydrophobic structure of esterified agar could promote the encapsulation of CUR (70.3 %). The release process is controlled by pH, and the release of CUR under weak alkaline conditions is significant, which can be explained by the pore structure, swelling characteristics, and carboxyl binding of agar. Therefore, this study shows the application potential of hydrogel microspheres in loading hydrophobic active ingredients and sustained release and provides the possibility for the application of agar in drug delivery systems.

Physicochemical properties and biological activities of Tremella hydrocolloids

In this paper, the physicochemical properties, antioxidant and anti-aging abilities of three new Tremella hydrocolloids were studied. The physicochemical properties were characterized by Fourier transform infrared spectroscopy, differential scanning calorimeter, X-ray diffractometry etc. The antioxidant activities of Tremella hydrocolloids were determined by ABTS radical, DPPH radical scavenging activity. The anti-aging ability of Tremella hydrocolloids was also investigated by using the organism model of Caenorhabditis elegans (C. elegans). The results showed that the ES-THD displayed the highest radical scavenging capacity and the best anti-aging abilities. The ability of ES-THD to scavenge ABTS radicals reached 100 % at 2 mg/mL, the ability of ES-THD to scavenge DPPH radicals reached 45.55 %. Compared with the control group, the average lifespan was 29.17 % longer fed with ES-THD. These results provide the evidence basis for the use of Tremella hydrocolloids as food texture modifiers, antioxidants, and anti-aging agents in the food industries.

Photo-Phytotherapeutic Gel Composed of Copaifera reticulata, Chlorophylls, and k-Carrageenan: A New Perspective for Topical Healing

Chronic wound healing represents an impactful financial burden on healthcare systems. In this context, the use of natural products as an alternative therapy reduces costs and maintains effectiveness. Phytotherapeutic gels applied in photodynamic therapy (PDT) have been developed to act as topical healing medicines and antibiotics. The bioactive system is composed of Spirulina sp. (source of chlorophylls) and Copaifera reticulata oil microdroplets, both incorporated into a polymeric blend constituted by kappa-carrageenan (k-car) and F127 copolymer, constituting a system in which all components are bioactive agents. The flow behavior and viscoelasticity of the formulations were investigated. The photodynamic activity was accessed from studies of the inactivation of Staphylococcus aureus bacteria, the main pathogen of hospital relevance. Furthermore, in vivo studies were conducted using eighteen rabbits with dermatitis (grade III and IV) in both paws. The gels showed significant antibiotic potential in vitro, eliminating up to 100% of S. aureus colonies in the presence or absence of light. The k-car reduced 41% of the viable cells; however, its benefits were enhanced by adding chlorophyll and copaiba oil. The animals treated with the phytotherapeutic medicine showed a reduction in lesion size, with healing and re-epithelialization verified in the histological analyses. The animals submitted to PDT displayed noticeable improvement, indicating this therapy's viability for ulcerative and infected wounds. This behavior was not observed in the iodine control treatment, which worsened the animals' condition. Therefore, gel formulations were a viable alternative for future pharmaceutical applications, aiming at topical healing.

The improvement of texture properties and storage stability for kappa carrageenan in developing vegan gummy candies

BACKGROUND

As plant-based foods have become more mainstream in recent years, carrageenan has been used to replace animal-derived gelatin in confectionery products. However, texture defects and water seepage during storage limit the development of kappa carrageenan (KC) gummy candies.

RESULTS

This study evaluated the effects of hydrocolloids on the texture properties and storage stability of KC gummy candies. The results showed that 4 g kg^-1 carboxymethylcellulose (CMC) composited with 20 g kg^-1 KC formed a flexible gummy candy with low fragility and limited water seepage during storage. Further investigation revealed that 4 g kg^-1 CMC promoted side-by-side intermolecular aggregation of KC helices through hydrogen bonding, which stabilized a denser network structure compared to the pure KC hydrogel. However, high CMC proportions (8-12 g kg^-1 ) led to electrostatic repulsion that dominated in the system, inhibiting the gel-forming process and thus resulting in a weak gel structure with accelerated syneresis.

CONCLUSION

This study found that 4 g kg^-1 CMC was able to improve the flexibility and decrease unacceptable fragility of KC gummy candies, with water seepage decreased during storage significantly. It provided preliminary evidence for utilizing hydrocolloids to adjust texture and control water migration in KC gels, and has potential to promote wide development of vegan gummy candies. © 2021 Society of Chemical Industry.

Rheological and gelling properties of Nicandra physalodes (Linn.) Gaertn. pectin in acidic media

Nicandra physalodes (Linn.) Gaertn. polysaccharide (NPGP) was previously recognized as a pectic polysaccharide, with a high galacturonic acid content (87.8%) and a low methoxylation degree (28%). In the present study, it was found that NPGP can form self-supporting gels when cooling its heated solutions (2.0%, w/v) acidified by citric acid. It was demonstrated that the decrease in pH led to the suppression in electrostatic repulsions between the pectin chains, thereby promoting pectin chain-chain association mainly through hydrogen bonding. As the pH decreased from 3.2 to 2.4, the gel strength and gel thermal stability were continuously increased. Moreover, it was shown that sucrose addition slightly promoted the gelation and gel thermal stability of NPGP, but the effect of monovalent ions (Na⁺) and divalent ions (Ca²⁺) was not significant. Conclusively, our results indicate that NPGP is a new gelling polysaccharide that shows great potential in formulation of acidic gel foods.

Construction of Artemisia sphaerocephala Krasch. Polysaccharide based hydrogel complexed with pullulan and gelatin crosslinked by ferric ions

Artemisia sphaerocephala Krasch. polysaccharide (ASKP) was found to be crosslinked with ferric ions to form hydrogels in the previous study. In this work, it was demonstrated that ASKP-Fe³⁺ hydrogel complexed with pullulan or gelatin contributed to a significantly enhanced gel strength at 1.5% ASKP, 60 mM Fe²⁺, pH 4.0, and the mixing ratio of 9: 1. The complexed hydrogels presented a dense semi-interpenetrating network along with the delay of gelation time and the increase of water retention. ASKP based complexes exhibited good compatibility, probably because pullulan and gelatin could be entangled with ASKP chain under hydrogen bonding and electrostatic interaction, respectively. The interaction between ASKP and pullulan or gelatin contributed to the formation of complexed hydrogels with dense network and significantly enhanced gel strength. It is inferred that ASKP would have great potential to be a new gelling material as well as for the ferric ions delivery.

Synthesis and properties of maleic anhydride-modified agar with reversibly controlled gel strength

Agar is modified by chemical methods to improve its functional properties and meet the increasing demand of the market. Some of the functional properties of agar are improved after chemical modification, while other properties are reduced, especially gel strength. This study aimed to comprehensively improve the functional properties of agar through acylation and crosslinking by reacting with maleic anhydride. ¹³C NMR indicated the maleylation reaction was preferred at the C2 hydroxyl group of D-galactose, and the crosslinking reactions occurred at the C2 and C6 hydroxyl groups of D-galactose in different agar chains. Interestingly, the maleylated agar monoester had higher gel transparency (1.5%, w/v) of up to 76% than the native agar (58%). However, it showed a significant decrease in gel strength from 783 g/cm² to 403 g/cm², while crosslinking endowed agar with higher gel strength (845 g/cm²) and gel transparency (78.4%). The high transparency of the modified agar plate made colony observation and colony counting easy. Maleylation of agar further enhanced the freeze-thaw stability of agar gel (24.8%, 7th freeze-thaw cycles). Overall, the maleylated agar possessed superior functional properties, and it could be used as food, bacteriological, and biotechnological agar.

Sodium Alginate and Chitosan as Components Modifying the Properties of Inulin Hydrogels

The aim of the study was to investigate the influence of addition of sodium alginate (SA) and chitosan (CH) on the properties of inulin hydrogels. Inulin hydrogels (20 g/100 g) containing various additions (0.0, 0.1, 0.3, and 0.5 g/100 g) of SA and CH were produced. The hydrogels' properties were assessed based on the volumetric gel index, microstructure, yield stress, texture, stability, and color parameters. According to the findings, the inclusion of these polysaccharides had no influence on the gelation ability of the inulin solution. The physical properties of the hydrogels containing SA or CH differed from hydrogels containing only inulin (INU). The obtained microstructural pictures revealed that the addition of SA and CH resulted in the formation of hydrogels with a more compact, smooth, and cohesive structure. Consequently, they had higher yield stress, strength, and spreadability values than INU hydrogels. The addition of chitosan in comparison with sodium alginate also had a greater effect in strengthening the structure of hydrogels, especially at the level of 0.5 g/100 g. For example, the addition of this amount of SA increased the yield stress on average from 195.0 Pa (INU) to 493.6 Pa, while the addition of CH increased it to 745.3 Pa. In the case of the strength parameter, the addition of SA increased the force from 0.24 N (INU) to 0.42 N and the addition of CH increased it to 1.29 N. In the case of spreadability this increase was from 2.89 N * s (INU) to 3.44 N * s (SA) and to 6.16 N * s (CH). Chitosan also caused an increase in the stability of inulin hydrogels, whereas such an effect was not observed with the addition of sodium alginate. The gels with the addition of SA and CH also had significantly different values of color parameters. Inulin-alginate hydrogels were characterized by higher values of the color parameter a *, lower values of the color parameter b *, and in most concentrations higher values of the color parameter L * compared to inulin-chitosan hydrogels. Based on the collected data, it can therefore be concluded that through the addition of sodium alginate and chitosan, there is a possibility to modify the properties of inulin hydrogels and, consequently, to better adapt them to the characteristics of the pro-health food products in which they will be used.

Effects and mechanism of sucrose on retrogradation, freeze-thaw stability, and texture of corn starch-tamarind seed polysaccharide complexes

In this work, we investigated the effects of sucrose (0%-30%, w/w) on the pasting properties, retrogradation, freeze-thaw stability, texture, and the possible interaction with corn starch-tamarind seed polysaccharide (CS-TSP) mixtures. Sucrose increased the gelatinization temperature (from 76.4 ± 0.1 to 87.6 ± 0.0°C), peak viscosity (from 3358.0 ± 1.4 to 7732.5 ± 44.5 cP), and final viscosity (from 3514.0 ± 31.1 to 7724.5 ± 142.1 cP) of CS-TSP mixtures. Further, sucrose limited the increase in the storage modulus of the mixture pastes, transfer of bound water to free water, and water syneresis during the freeze-thaw process. Additionally, sucrose resulted in a more complete gel structure with stronger resistance. Scanning electron microscope and fluorescence labeling analysis showed that the presence of sucrose helped in tight entanglement or cross-link between amylose or between amylose and TSP. Thus, these results in this study could help to improve physicochemical properties of starch-based products, such as glue pudding and other starch desserts.

Rheological and textural analysis as tools for investigation of drug-polymer and polymer-polymer interactions on the example of low-acyl gellan gum and mesalazine

PURPOSE

In the performed study, the rheological and textural parameters of gellan-based hydrogels were investigated and their dependence on three factors was taken into consideration: (i) The presence of the model drug, (ii) The presence and type of the ionic crosslinking agent, and (iii) the composition of the polymer network. The objective was to compare two analytical methods, regarded as complementary, and define to what extent the obtained results correlate with each other.

METHODS

The hydrogels contained low-acyl gellan gum or its mixtures with hydroxyethyl cellulose or κ-carrageenan. CaCl₂ and MgCl₂ were used as gelling agents. Mesalazine was used as a model drug. The rheological analysis included oscillatory stress and frequency sweeping. The texture profile analysis was performed to calculate texture parameters.

RESULTS

Placebo gels without the addition of gelling agents had the weakest structure. The drug had the strongest ability to increase the stiffness of the polymer network. The weakest structure revealed the placebo samples without the addition of gelling agents. Texture analysis revealed no significant influence of the drug on the strength of the gels, while rheological measurements indicated clear differences.

CONCLUSIONS

It can be concluded that in the case of some parameters methods correlate, that is, the effect related to gelling ions. However, the rheological analysis seems to be more precise and sensitive to some changes in the mechanical properties of the gels.

Fucoidan hydrogels induced by κ-carrageenan: Rheological, thermal and structural characterization

Fucoidan (FUC) is a non-gelling polysaccharide but could interact with κ-carrageenan (KC) to form a stable gel blend. However, their interaction mechanism is unclear. Herein, FUC and KC blended gels are prepared by mixing FUC (10 and 20 mg/mL) and KC (6, 7 and 8 mg/mL) solutions, and characterized through LF-NMR, rheology, DSC, Cryo-SEM, and FTIR. The FTIR analysis confirms the formation of hydrogen bonds between FUC and KC chains. The KC addition to FUC significantly improves the water retention and frost resistance. The viscoelastic measurements reveal higher gelling nature of the FUC-KC binary mixtures, and the DSC results confirm the higher thermal stability. The Cryo-SEM images clearly reveal the gel network structure. The outcome of this study deemed to further the FUC use in food and non-food applications.

A novel meat quality improver composed of carrageenan and superfine smashed okra powder and its application in chicken meatballs

The study investigated the effects of the addition of 0% (control group, CG), 0.25, 0.35, and 0.45% superfine smashed okra powder (SSOP) or carrageenan (CAR), and 0.25% SSOP – 0.35% CAR complex (OC) on the quality of chicken meatballs. Chicken meatballs fabricated with the SSOP-CAR complex showed better quality as compared to the other treatments. The lowest cooking loss was observed in the OC group, which corresponded to significantly decreased relaxation times of low-field nuclear magnetic resonance (LF-NMR) (T 21 and T 22) (P < 0.05). Compared to CG, The L* and a* values of chicken meatballs were significantly decreased due to the addition of SSOP (P < 0.05), and the additions of SSOP and CAR significantly increased the storage modulus (G′) and loss modulus of chicken meat batter upon heating (P < 0.05). Besides, the OC and 0.45% CAR groups showed the highest texture profile values for hardness and chewiness (P < 0.05). The sensory evaluation revealed that the chicken meatballs emulsified with the OC had the best overall acceptability. The results indicated that OC could be a great feasible and potential application in the meat industry, especially in the development of functional emulsified meat products.

Synergistic gelling mechanism of RG-I rich citrus pectic polysaccharide at different esterification degree in calcium-induced gelation

RG-I rich pectic polysaccharide is common in fruit and vegetable and possesses health benefits. However, it is removed during commercial pectin production because of poor gelling properties. Synergistic gelation can improve rheological properties of RG-I pectic polysaccharide and expand its application in functional food hydrocolloids. In the study, RG-I rich pectic polysaccharides at different degree of esterification was extracted from citrus membrane by sequential mild acidic (0.4% HCl, 28 °C) and alkaline (0.6% NaOH, 32 °C) treatment. The pectic polysaccharide from acid water (PA) composes of 41% RG-I and 44% HG with DM of 45%, while the pectic polysaccharide from basic water (PB) composed of 63% RG-I and 19% HG with DM of 15%. PA/PB blend gel under CaCO₃-glucono-δ-lactone system showed improved rheological properties compared with pure gels. Ca-bridges connected pectin aggregates and promoted the three-dimensional structure of PA/PB blend gels, while neutral sugar side-chains prompted hydrogen bonds and strengthened gel network.

Structure and physicochemical properties of amphiphilic agar modified with octenyl succinic anhydride

A novel amphiphilic agar with high transparency and freeze-thaw stability was prepared using octenyl succinic anhydride (OSA). Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy confirmed that the hydrophobic OS groups were successfully introduced in OSA-modified agar (OSAR) backbone. The OSAR showed higher emulsion stability and oil loading capacity than the native agar (NA). Compared with gel transparency (47.1 %), syneresis (42.1 %) of NA, OSAR exhibited high gel transparency (80 %) and low syneresis (3.3 %) when the degree of substitution (DS) was 0.06 and 0.12, respectively. Meanwhile, the OSAR showed a decreased interface tension and average molecular weight after modification. Thermogravimetric analysis indicated the thermal stability of OSAR was decreased, while texture profile analysis showed the springiness of the OSAR gel was enhanced. Dynamic rheology measurements revealed the OSAR with low gel strength displayed more liquid-like properties. Moreover, the OSAR exhibited lower turbidity and melting temperatures than the NA.

Influence of two functional dextrins on the gel properties of kappa-carrageenan

The physicochemical properties of κ-carrageenan (KC) can be improved by incorporation with small-molecule cosolvents. The texture and rheological properties, micromorphology, and crystallinity of KC incorporating indigestible dextrin (IDD) and beta-limit dextrin (BLD) were investigated. The rheological properties and sol-gel transition temperatures of the gels were slightly improved and the hardness of KC gels was significantly increased after the two dextrins were mixed in. Fourier transform infrared spectroscopy results indicated hydrogen-bonding interactions were strengthened in the presence of the dextrins. Confocal laser scanning microscope images revealed that a more homogenous structure was formed of the KC gel after the addition of dextrins. Moreover, X-ray diffraction patterns indicated the crystallinity of KC gel decreased upon dextrin addition. At the same dextrin content, IDD exerted a greater influence than BLD. IDD contents exceeding 3% (w/w) led to undesirable effects, whereas up to 5% (w/w) of BLD could be added. The two dextrins affected the rearrangement of the KC random coils in the sol state, and facilitated aggregation of the KC chains during cooling to form gel network structures after gelation. Therefore, the appropriate addition of these two dextrins can improve the texture and stability of KC gels and expand their application in functional foods.

Structural Properties, Bioactivities, and Applications of Polysaccharides from Okra [Abelmoschus esculentus (L.) Moench]: A Review

Okra [Abelmoschus esculentus (L.) Moench], as a kind of nutritive vegetable, is rich in flavonoids, polyphenols, polysaccharides, amino acids, and other bioactive substances and has various biological activities. As one of main bioactive components, okra polysaccharides (OPs), mainly comprising pectic polysaccharides, have various biological activities. OPs have been extensively investigated in recent years. Many studies characterized structures of OPs obtained by different extraction methods, which were confirmed to be rhamnogalacturonan-I-type polysaccharides in most cases. OPs have a thick and slimy texture, suggesting that they can be a promising source of texture modifiers for complex food matrices. They have various biological activities, such as antioxidant activity, immunomodulatory activity, hypoglycaemic activity, and improving intestinal function. Therefore, OPs may potentially serve as novel immunomodulators or an adjuvant for diabetic nephropathy. Up to now, there is no specific summary on the research progress of OPs. In this paper, the latest research progress on the extraction, purification, characterization, rheological properties, biological activities, and applications of OPs is reviewed, to provide the reference for the processing and comprehensive utilization of OPs in the future.

Okra polysaccharides/gelatin complex coacervate as pH-responsive and intestine-targeting delivery protects isoquercitin bioactivity

Okra polysaccharides (OPs) belong to RG I pectin branched with neutral saccharide side chains, which possesses distinctive structure and physicochemical properties from the commonly used HG pectin. Until now, the application of RG I pectin as wall material of microcapsule remains unclear. Here, we obtained OPs/gelatin complex coacervate at the maximum yield of 86.8% (pH 3.5, gelatin/OPs ratio 9:1 and 2% (w/v) total polymer concentration) by response surface methodology. Isoquercitin (IQ)-loaded OPs/gelatin complex coacervate (OGIQ) showed porous spongy-like surface structure with average particle size, encapsulation efficiency and surface porosity at 334 nm, 81.6% and 31.9%, respectively. OGIQ was found to be pH-responsive and intestine-targeting. The IQ-release rate of OGIQ was assayed to be 89.4% in intestine fluid and below 2% in acidic and simulated gastric digestion, respectively. Accordingly, embedding in OGIQ protected IQ in digestion and improved its postdigestive α-glucosidase inhibitory rate by 88.7%. The differential scanning calorimetry curves showed that OGIQ effectively prevented IQ from thermal decomposition. The XRD, FT-IR and CD spectra indicated that IQ was embedded in OGIQ in amorphous state by hydrogen bonds and electrostatic interaction. Compared with HG, the neutral saccharide side chains of OPs could induce different secondary conformation change of gelatin during complex coacervation.

The degree of compactness of the incipient High Methoxyl Pectin networks. A rheological insight at the sol-gel transition

Fractal analysis can be properly applied to complex structures, like physical and chemical networks formed by particles or polymers, when they exhibit self-similarity over an extended range of length scales and, hence, can be profitably used not only for their morphological characterization but also for individuating possible relationships between morphology and mechanisms of aggregation and crosslinking, as well as between morphology and physical properties. Several experimental methods are available to determine the fractal dimension of gel networks, including various scattering techniques and microscopies, permeability measurements and rheology. The present study regards the self-assembly kinetics of High Methoxyl Pectin (HMP) solutions with different pectin and sucrose concentrations investigated by rheological measurements to highlight the effects of pectin and sucrose concentrations on the gel point and to evaluate the degree of compactness of the incipient gel networks through an interpretation of the viscoelastic response at the sol-gel transition.

Green Synthesis of Mg0.99 Zn0.01O Nanoparticles for the Fabrication of κ-Carrageenan/NaCMC Hydrogel in order to Deliver Catechin

Currently, the role of the nanoparticles in the structure of the composites and their benefits for the health of the body is valuable. In this study, the effects of the doping on the structural and morphological properties of the hydrogels using a Mg co-doped ZnO hydrogel, which has been fabricated by the sol–gel process, have been investigated. Then, a hydrogel containing nanoparticle and a hydrogel without any nanoparticles was produced as a control. The hydrogels were loaded with catechin and the related characterization was evolved based on the new structure of the matrices. The Mg_0.99Zn_0.01O nanoparticles were synthesized using a green synthesis method. To investigate the properties of the nanoparticles, zeta potential and XRD were studied. The field emission scanning electron microscopy (FESEM), FTIR, TGA, swelling Ratio, and compression tests were investigated for the hydrogels. Based on the results, FESEM showed a more compressed structure for hydrogels including nanoparticles rather than the hydrogels without a nanoparticle. The TGA showed a higher decomposition temperature in the hydrogels including nanoparticles. The swelling ratio of hydrogels containing a nanoparticle was higher than the control hydrogel. κ-Carrageenan/ Mg_0.99Zn_0.01O/NaCMC/Catechin had the highest swelling ratio (44.15%) rather than the κ-Carrageenan/NaCMC (33.22%). Mg_0.99Zn_0.01O nanoparticles presented a stronger structure of hydrogels in the compression test. It is concluded that the role of the synthesized nanoparticle is critical in the structure of the hydrogel.

Extraction, purification, characterization, and rheological properties of a glycoprotein from Cynomorium songaricum Rupr

Cynomorium songaricum Rupr is widely known in China as a traditional herbal medicine. In this study, single-factor experiments and response surface methodology were used to optimize the extraction of Cynomorium songaricum Rupr glycoprotein (CSG). The results show that a maximum glycoprotein yield of 6.39 ± 0.32% was achieved at a ratio of solid to liquid 32:1 for 4.2 H at 52 °C. Then, the IR, monosaccharide composition, amino acid composition, type of glycopeptide linkage, and average molecular weight of CSG-1 purified from CSG were characterized. The results indicate that CSG-1 presented the characteristic absorption peak of polysaccharide and protein, including four monosaccharides and 17 amino acids, had O-linked glycopeptide bonds, M_w , W_n , M_w /M_n , M_p , and the z-average were 5.343 × 10⁶ , 3.203 × 10⁶ , 1.668, 8.911 × 10⁶ , and 6.948 × 10⁶ , respectively. Besides, CSG-1 solution was described by the Herschel-Bulkley model and it behaved as a shear-thinning fluid. Also, under a frequency sweep the moduli G' and G″ both increased with increasing CSG-1 concentration and the CSG-1 dispersions had weak thermal stability over the temperature sweep. These results provide a scientific basis for the further study of Cynomorium songaricum Rupr.