Rheological elucidation of the viscoelastic properties and network interaction of mixed high-methoxyl pectin and kappa-carrageenan gels

Influence of alkali treatment and ultrasonication on the bioactivities and rheological properties of sulfated polysaccharides

The rheological, antioxidant and anticoagulant properties of 17 different structurally uniform and hybrid sulfated polysaccharides are presented in this study. Alkali treatment was used to modify carrageenan precursors, while ultrasonication was employed to partially depolymerize polysaccharide chains. Native and modified sulfated polysaccharides with well-resolved molecular structures were characterized by size exclusion chromatography and dynamic rheometry methods. Extensive ultrasonication (1-64 min) reduced the molecular weights of the samples from approximately 384-1156 kDa to 47-95 kDa. Their rheological properties showed strong dependence on molecular weight, with gelling ability decreasing in the order: furcellaran, kappa carrageenan > iota carrageenan, funoran > lambda carrageenan > theta carrageenan, sulfated chitosan. The anticoagulant activity, measured via aPTT assay, followed the order: lambda carrageenan > iota carrageenan, kappa/iota carrageenan, carrageenan mixture, sulfated chitosan > theta carrageenan > kappa carrageenan, funoran. Among the antioxidant properties determined using Folin-Ciocalteu, DPPH, ABTS, OH radical, and FRAP assays, OH radical scavenging activity was particularly noteworthy, being inherent to all polysaccharides and displaying a correlation with molecular weight. These results validate the interdependence of alkali treatment and the molecular weights of both natural and chemically sulfated polysaccharides in influencing their respective anticoagulant and antioxidant activities measured using in-vitro assays.

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.

High-concentration hydrogels of κ-carrageenan prepared using subcritical water

κ-Carrageenan hydrogels have been prepared at very high concentrations beyond the previous limit of conventional κ-carrageenan hydrogels. By dissolving κ-carrageenan using subcritical water at 150 °C, homogeneous translucent hydrogels have been obtained from 15 wt% to 40 wt%. The high-concentration hydrogels have exceptionally high Young's modulus (E0) ranging 106-107 Pa and exhibit an unknown concentration (c)-dependence of E0 ∝ c1.0-1.1. The distinctive mechanical properties of the high-concentration hydrogels are also demonstrated by modifying the stress (σ)-strain (ε) curves. Curves of σ / E0 versus ε for the high-concentration hydrogels seem to fall on a single curve that is remarkably different from that for the conventional 3 wt% hydrogel. The gel-to-sol transition temperature (Tm) proves high thermal resistance of the high-concentration hydrogels; Tm increases with c and exceeds 100 °C at 30 wt% and 40 wt%. It has been confirmed that separated pieces of high-concentration hydrogels are unified into a single disk above Tm. The endothermic enthalpy of the gel-to-sol transition per unit weight of κ-carrageenan is almost constant regardless of c among the high-concentration hydrogels, which is consistent with the claim that the high-concentration hydrogels have similar distinctive network structure.

Blending pectin and κ-carrageenan converted the liquid yogurt induced by pectin into the solid yogurt

Effects of 0.11 %-0.17 % pectin and the mixture of 0.03 % κ-carrageenan and 0.11 %-0.17 % pectin on texture and microstructure of yogurt were investigated in this work. Rheology analysis demonstrated that adding 0.11 %-0.17 % pectin before fermentation inhibited gelation of yogurt and liquid yogurt was formed. However, when the above κ-carrageenan/pectin mixture was added, yogurt was gelled and solid-like. It was demonstrated by CLSM that milk protein aggregated into separated particles in the liquid yogurt induced by pectin, while milk protein aggregated into a continuous network in the solid yogurt induced by the mixture. Adding 0.11 %-0.17 % pectin into the casein micelle suspension induced aggregation of casein micelles into separated particles, which was the same in the corresponding liquid yogurt samples. Moreover, casein micelles precipitated in the pectin/casein micelle mixtures after storage for 3 h. However, when the above mixture was added into the casein micelle suspension, tightly-connected casein micelle aggregates appeared and the resultant κ-carrageenan/pectin/casein micelle mixtures were stable after storage for 3 h. These results indicated that the pectin-casein micelle interaction played an essential role in formation of the liquid yogurt and κ-carrageenan altered this interaction. Thus, blending κ-carrageenan and pectin converted the liquid yogurt induced by pectin into the solid yogurt.

Structure formation mechanism of pectin-soy protein isolate gels: Unraveling the role of peach pectin fractions

This study investigated the macro & micro properties of the composite gels formed by soy protein isolate (SPI) and peach pectin fractions: water-soluble pectin (WSP), chelator-soluble pectin (CSP), and sodium carbonate soluble pectin (NSP). Specially, the interaction between pectin fractions and SPI was studied to explain the formation mechanism of the composite gels. WSP, as a high methoxyl pectin, exhibited rich branching (sugar ratio B = 3.10). CSP, as a low methoxyl pectin, depicted a high linearity. NSP, with low linearity (sugar ratio A = 6.14), contained numerous side chains. Due to the strong interaction between pectin fractions and SPI, the new composites with excellent dense network microstructures were formed, accompanied by increased apparent viscosity, higher G' and G'', and reduced particle size. XRD and FT-IR analysis highlighted the modifications in gel structures. SEM-dispersive X-ray spectroscopy observed elemental distribution and framework composition in pectin-SPI gels. Hydrophobic interaction was the most important chemical force in pectin-SPI binding. Molecular docking results indicated that galacturonic acid in pectin bound more strongly to 7S than to 11S, with tighter hydrogen bonds. Notably, WSP-SPI showed the lowest turbidity, indicating enhanced solubility and particle dispersion, which helped prevent aggregation. CSP-SPI demonstrated the highest G' and G'', ascribing to the high linearity and abundant carboxyl groups in CSP. NSP-SPI showed the highest apparent viscosity and irregular structure. Overall, the texture properties of pectin-SPI gels were driven by pectin's structure properties, which would provide new and valuable information for texture control in gel formulation.

Quality Evaluation of Chicken Liver Pâté Affected by Algal Hydrocolloids Addition: A Textural and Rheological Approach

Hydrocolloids are used in spreadable meat or poultry products to improve consistency, emulsion stability and water retention, resulting in products with desired functional and organoleptic properties. The scope of the work was to evaluate the addition of three divergent algal hydrocolloids (κ-carrageenan, ι-carrageenan, furcellaran) at four different concentrations (0.25, 0.50, 0.75, and 1.00% w/w) on the physicochemical, textural, rheological and organoleptic properties of model chicken liver pâté (CLP) samples. Overall, the highest hardness and viscoelastic moduli values of the CLP samples were reported when κ-carrageenan and furcellaran were utilized at a concentration of 0.75% w/w (p < 0.05). Furthermore, increasing the concentrations of the utilized hydrocolloids led to increase in the viscoelastic moduli and hardness values of CLP. Compared to the control sample, an increase in spreadability was reported in the CLP samples with the addition of hydrocolloids. Finally, the use of algal hydrocolloids proved to be an effective way to modify the techno-functional properties of CLP.

Recent advances in 3D printing properties of natural food gels: Application of innovative food additives

Recent advances in 3D printing technology have provided a new avenue for food manufacturing. However, one challenge in 3D printing food is the limited availability of printable materials that can mimic the properties of real food. This review focused on the various 3DFP methodologies, as well as the reinforcement of natural food gel for improving printing features in 3D printed food. Also covered is the use of hydrogel-based 3D printing in the development of 3D printed food. Different 3D printing techniques can be employed to print hydrogel-based inks, each with its advantages and limitations. 3D printing of food using hydrogel-based inks has potential for customized food products development. In summary, the utilization of hydrogel-based inks in 3D printing offers a promising avenue for the development of customized food products. Although there are still challenges to overcome, such as improving the printability and mechanical properties of hydrogel-based inks, the potential benefits of this technology make it an exciting area of research.

Konjac glucomannan-based aerogels with excellent thermal stability and flame retardancy for thermal insulation application

Biomass aerogels are a promising kind of environment-friendly thermal insulation material. However, the flammability, poor water resistance, and thermal instability of biomass aerogels limit their applications. Herein, freeze-drying and thermal imidization were used to create konjac glucomannan (KGM), boron nitride (BN), and polyimide (PI)-based aerogels with a semi-interpenetrating network structure. The introduction of BN was beneficial to improve the mechanical properties and thermal stability of aerogels. The imidization process of PI improved the hydrophobicity, mechanical property, and flame retardancy of the aerogels. The synergistic effect of PI and BN reduced the peak heat release rate and total heat release rate of KGM-based aerogel by 55.8 % and 35 %, respectively, and endowed aerogel with good self-extinguishing performance. Moreover, the results of thermal conductivity and infrared thermal imaging demonstrated that the aerogels had excellent thermal insulation properties, and could effectively manage thermal energy over a wide range of temperatures. This study provides a simple method for the preparation of heat-insulating aerogel with high fire safety, which has broad application prospects in the field of energy saving and emission reduction.

Extraction and characterization of a pectin from sea buckthorn peel

Sea buckthorn peel is the by-product of the sea buckthorn processing, which contains many bioactive compounds. In this paper, sea buckthorn high methoxyl pectin (SBHMP) was obtained, with a yield of 8% and a light-colored. The SBHMP was a high methoxyl with a degree of esterification of 57.75% and uronic acid content of 65.35%. The structural and morphological characterization of SBHMP were analyzed by high-performance liquid chromatography, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Results showed that SBHMP presented a sheet and layered stacked morphological, and was mainly composed of galacturonic acid, arabinose, galactose, rhamnose, and mannose, which indicated that SBHMP mainly consisted of homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) type pectin polysaccharides. In addition, SBHMP also presented significant gel, thickening, and emulsifying properties. The results exhibited that SBHMP could form jelly-like gels under acid and high sucrose conditions, presenting a shear-thinning behavior and increasing apparent viscosity with the enhancement of pectin and sucrose contents. Besides, SBHMP could form oil-in-water emulsions with pectin concentrations of 1.0–3.0%. When the SBHMP concentrations were 2.0 and 3.0%, the emulsions were stable during 7 days of storage. Findings in this paper demonstrated the potential of SBHMP to be a food thickener and emulsifier and support the in-depth utilization of sea buckthorn by-products.

Effects of gelation concentration on cyclic deformation behavior of κ-carrageenan hydrogels

The aim of this study is to elucidate the relationship between the network structure of κ-carrageenan hydrogels and their mechanical properties. First κ-carrageenan hydrogels have been prepared at different gelation concentrations, and then the mechanical behavior during four cyclic deformations has been examined at the same κ-carrageenan concentration. Young's modulus is higher for the gel prepared at 5 gL^-1 (C05) compared to that for the gel prepared at 30 gL^-1 (C30). C30 shows almost linear relation between the stress and the strain like an ideal rubber, while a residual strain appears in each cyclic deformation for C05. The extent of the residual strain depends on the maximum strain and the deformation speed, indicating that C05 deforms plastically to some extent. The residual strain for C05 decreases gradually even after a cyclic deformation and disappears in the case of a small strain as if there were a memory of the structure. The effects of the gelation concentration on the mechanical properties have been explained based on the network structure specific to κ-carrageenan hydrogels. The higher modulus for C05 has been attributed to the higher helix content and the plastic deformation of C05 to the loosely-aggregated crosslinks.