Effects of pH, extrusion tip size and storage protocol on the structural properties of Ca(II)-alginate beads

Fabrication of food polysaccharide, protein, and polysaccharide-protein composite gels via calcium ion inducement: Gelation mechanisms, conditional factors, and applications

Food gel is a kind of macromolecular biopolymer with viscoelasticity, which has good water retention and gelling ability, especially gels formed by protein and/or polysaccharide. The addition of calcium ions triggers gelation by interacting with the gel matrix, enhancing gels' textural and rheological properties like hardness, viscosity and elasticity. Thus calcium ions enrich the range of applications of food gels. This review focuses on forming a calcium-induced gel and improving the texture properties. It summarizes the mechanisms of gelation induced by calcium ions in polysaccharide, protein, and polysaccharide-protein systems and their gel properties. The effects of influencing factors in calcium ion concentration, types and mixing ratios of matrices, acid, and alkaline environments, as well as treatment methods on calcium-induced gel characteristics, are presented. Additionally, the current applications of calcium-induced gels in food industries and challenges are presented.

Alginate-Bentonite Encapsulation of Extremophillic Bacterial Consortia Enhances Chenopodium quinoa Tolerance to Metal Stress

This study explores the encapsulation in alginate/bentonite beads of two metal(loid)-resistant bacterial consortia (consortium A: Pseudomonas sp. and Bacillus sp.; consortium B: Pseudomonas sp. and Bacillus sp.) from the Atacama Desert (northern Chile) and Antarctica, and their influence on physiological traits of Chenopodium quinoa growing in metal(loid)-contaminated soils. The metal(loid) sorption capacity of the consortia was determined. Bacteria were encapsulated using ionic gelation and were inoculated in soil of C. quinoa. The morphological variables, photosynthetic pigments, and lipid peroxidation in plants were evaluated. Consortium A showed a significantly higher biosorption capacity than consortium B, especially for As and Cu. The highest viability of consortia was achieved with matrices A1 (3% alginate and 2% bentonite) and A3 (3% alginate, 2% bentonite and 2.5% LB medium) at a drying temperature of 25 °C and storage at 4 °C. After 12 months, the highest viability was detected using matrix A1 with a concentration of 106 CFU g-1. Further, a greenhouse experiment using these consortia in C. quinoa plants showed that, 90 days after inoculation, the morphological traits of both consortia improved. Chemical analysis of metal(loid) contents in the leaves indicated that consortium B reduced the absorption of Cu to 32.1 mg kg-1 and that of Mn to 171.9 mg kg-1. Encapsulation resulted in a significant increase in bacterial survival. This highlights the benefits of using encapsulated microbial consortia from extreme environments, stimulating the growth of C. quinoa, especially in soils with metal(loid) levels that can be a serious constraint for plant growth.

Micellar Nanogels from Alginate-Based Diblock Copolysaccharides

Alginates are marine polysaccharides known for their ability to selectively bind calcium ions and form hydrogels. They are widely used in biomedical applications but are challenging to produce as nanogels. Here we introduce a self-assembly route to create stable alginate-based nanogels under near-equilibrium conditions. Guluronate (G) blocks, which interact with divalent cations such as Ca2+, Ba2+, and Sr2+, were extracted from alginates and covalently linked through their reducing end to the reducing end of dextran (Dex) chains, forming linear block copolymers that self-assemble into micellar nanogels with a core-corona structure in the presence of these ions. Real-time dynamic light scattering (DLS) and small-angle neutron scattering (SANS) were used to study the self-assembly mechanism of the copolymer during dialysis against divalent ions. For the G12-b-Dex51 copolymer, we achieved spherical micelles with an 8 nm radius and an aggregation number of around 20. Although the type of divalent cation affected micelle stability, it did not influence their size. Micellar nanogels are dynamic structures, capable of ion exchange, and can disassemble with chelating agents like ethylenediamine tetraacetic acid (EDTA).

In Vitro Digestion and Fermentation of Cowpea Pod Extracts and Proteins Loaded in Ca(II)-Alginate Hydrogels

Antioxidants derived from food by-products are known for their bioactive properties and impact on human health. However, the gastrointestinal behavior is often poor due to their degradation during digestion. The development of Ca(II)-alginate beads supplemented with biopolymers and enriched with cowpea (Vigna unguiculata) extract could represent a novel environmentally friendly technological solution to produce functional ingredients in the food industry. The present study evaluates the impact of in vitro digestion/fermentation by analyzing global antioxidant response (GAR), production of short-chain fatty acids (SCFAs) as a modulation of gut microbiota, and behavior of proton transverse relaxation times by low-field nuclear magnetic resonance (as an indicator of gelation state and characterization of microstructure). Results revealed that guar gum and cowpea protein preserved a high GAR of total phenolic compounds and antioxidant capacity by ABTS and FRAP methods after digestion/fermentation, promoting an adequate protection of the bioactives for their absorption. Alginate-based beads have great potential as prebiotics, with the guar gum-containing system contributing the most to SCFAs production. Finally, the overall higher mobility of protons observed in the intestinal phase agrees with structural changes that promote the release of phenolic compounds during this stage. Beads are excellent carriers of bioactive compounds (cowpea phenolic compounds and peptides) with potential capacities.

Probiotic Encapsulation: Bead Design Improves Bacterial Performance during In Vitro Digestion (Part 2: Operational Conditions of Vibrational Technology)

The development of functional foods is a viable alternative for the prevention of numerous diseases. However, the food industry faces significant challenges in producing functional foods based on probiotics due to their high sensitivity to various processing and gastrointestinal tract conditions. This study aimed to evaluate the effect of the operational conditions during the extrusion encapsulation process using vibrating technology on the viability of Lactobacillus fermentum K73, a lactic acid bacterium with hypocholesterolemia probiotic potential. An optimal experimental design approach was employed to produce sweet whey-sodium alginate (SW-SA) beads with high bacterial content and good morphological characteristics. In this study, the effects of frequency, voltage, and pumping rate were optimized for a 300 μm nozzle. The microspheres were characterized using RAMAN spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy. The optimal conditions for bead production were found: 70 Hz, 250 V, and 20 mL/min with a final cell count of 8.43 Log10 (CFU/mL). The mean particle diameter was 620 ± 5.3 µm, and the experimental encapsulation yield was 94.3 ± 0.8%. The INFOGEST model was used to evaluate the survival of probiotic beads under gastrointestinal tract conditions. Upon exposure to in vitro conditions of oral, gastric, and intestinal phases, the encapsulated viability of L. fermentum was 7.6 Log10 (CFU/mL) using the optimal encapsulation parameters, which significantly improved the survival of probiotic bacteria during both the encapsulation process and under gastrointestinal conditions compared to free cells.

Probiotic Encapsulation: Bead Design Improves Bacterial Performance during In Vitro Digestion

The stability and release properties of all bioactive capsules are strongly related to the composition of the wall material. This study aimed to evaluate the effect of the wall materials during the encapsulation process by ionotropic gelation on the viability of Lactobacillus fermentum K73, a lactic acid bacterium that has hypocholesterolemia probiotic potential. A response surface methodology experimental design was performed to improve bacterial survival during the synthesis process and under simulated gastrointestinal conditions by tuning the wall material composition (gelatin 25% w/v, sweet whey 8% v/v, and sodium alginate 1.5% w/v). An optimal mixture formulation determined that the optimal mixture must contain a volume ratio of 0.39/0.61 v/v sweet whey and sodium alginate, respectively, without gelatin, with a final bacterial concentration of 9.20 log10 CFU/mL. The mean particle diameter was 1.6 ± 0.2 mm, and the experimental encapsulation yield was 95 ± 3%. The INFOGEST model was used to evaluate the survival of probiotic beads in gastrointestinal tract conditions. Upon exposure to in the vitro conditions of oral, gastric, and intestinal phases, the encapsulated cells of L. fermentum decreased only by 0.32, 0.48, and 1.53 log10 CFU/mL, respectively, by employing the optimized formulation, thereby improving the survival of probiotic bacteria during both the encapsulation process and under gastrointestinal conditions compared to free cells. Beads were characterized using SEM and ATR-FTIR techniques.

Structural and mechanical analysis on mannuronate-rich alginate gels and xerogels beads based on Calcium, Copper and Zinc as crosslinkers

Beads based on a mannuronate(M)-rich alginate (86 % M units) were prepared by adding the polysaccharide solution to a crosslinking bath containing different concentrations (0.5, 2 and 10 wt%) of XCl2 where X = Ca, Cu or Zn. Primarily focus was on Zn, due to its antioxidant, anti-inflammatory and anti-microbial capabilities. The beads were characterized by Field-Emission Scanning Electron Microscopy (FESEM), Fourier-Transform Infra-Red spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Small-Angle X-ray Scattering (SAXS) and compression tests. The crosslinking agent significantly influenced the properties of the resulting beads. Specifically, Ca-based beads exhibited a smoother surface, while Cu- and Zn-based beads appeared rougher. Interestingly, Zn-based beads displayed a core-shell structure. Young moduli ranged from 3500 and 7000 MPa, with the highest values observed for Zn-beads. SAXS investigation at 0.5 wt% XCl2 suggested increase in the densely packed domains amount in the order: Ca < Cu < Zn. Extended X-ray Absorption Fine Structure (EXAFS) showed that the coordination number was 4.3 ± 0.4 for Cu, and 4.0 ± 0.2 and 1.1 ± 0.1 for Zn in 0.5 wt% XCl2 alginate xerogels, in agreement with reported Density Functional Calculations on Cu2+- and Zn2+-MM complexes. The results from FT-IR, compositional analysis and EXAFS collectively suggested a bridging coordination for these systems.

Focusing on papain release in the intestine: The effects of Chitinous materials on alginate microsphere properties

Exogenous enzymes, accompanied by a function of assisting digestion, can be employed in therapeutic application which supplement the daily diet for the patients suffering from gastrointestinal diseases. To prevent the degradation of the enzymes in gastric fluid, papain was encapsulated into alginate microspheres with the external wrap of chitin nanocrystals. The protective effect of the assembled alginate microspheres (PAM‐ChNC) on papain was studied and compared with traditional chitosan‐coated alginate microspheres (PAM‐Ch). Scanning electron microscopy results showed that ChNC could form a dense structure on the surface of alginate microspheres. The swelling rate of PAM‐ChNC was lower than that of PAM‐Ch at pH 1.2. The effect of papain (encapsulated in microspheres) on the digestion of myofibrillar protein gels (MP) was investigated by in vitro digestion. The results showed that the degree of hydrolysis of MP + PAM‐ChNC was significantly higher than that of MP+ PAM‐Ch, indicating that PAM‐ChNC was expected to become a controlled release system for oral exogenous enzymes that assist digestion.

Binary Alginate-Whey Protein Hydrogels for Antioxidant Encapsulation

Encapsulation of antioxidants in hydrogels, i.e., three-dimensional networks that retain a significant fraction of water, is a strategy to increase their stability and bioaccessibility. In fact, low oxygen diffusivity in the viscous gelled phase decreases the rate of oxidation. Moreover, some hydrocolloids such as alginate and whey proteins provide a pH-dependent dissolution mechanism, allowing the retention of encapsulated compounds in the gastric environment and their release in the intestine, where they can be absorbed. This paper reviews the information on alginate-whey protein interactions and on the strategies to use binary mixtures of these polymers for antioxidant encapsulation. Results showed that alginate and whey proteins strongly interact, forming hydrogels that can be modulated by alginate molecular mass, mannuronic acid: guluronic acid ratio, pH, Ca2+ or transglutaminase addition. Hydrogels of alginate and whey proteins, in the forms of beads, microparticles, microcapsules, and nanocapsules, generally provide better encapsulation efficiency and release properties for antioxidants with respect to the hydrogel of alginate alone. The main challenges for future studies are to extend knowledge on the interactions among three components, namely alginate, whey proteins, and the encapsulated bioactive compounds, and to investigate the stability of these structures under food processing conditions. This knowledge will represent the rationale basis for the development of structures that can be tailored to specific food applications.

Ethanol-free Cross-Linking of Alginate Nanofibers Enables Controlled Release into a Simulated Gastrointestinal Tract Model

The use of alginate nanofibers in certain biomedical applications, including targeted delivery to the gut, is limited because an ethanol-free, biocompatible cross-linking method has not been demonstrated. Here, we developed water-stable, alginate-based nanofibers by systematically exploring post-electrospinning cross-linking approaches that used calcium ions dissolved in (1) a glycerol/water cosolvent system and (2) acidic, neutral, or basic aqueous solutions. Scanning electron microscopy proved that the fibers cross-linked in a glycerol cosolvent or pH-optimized solutions had maintained the same morphology as the ethanol-based literature control. Notably, cross-linked fibers were generally smaller in diameter than the as-spun fibers due to both chemical interactions and mass loss during cross-linking, which was supported by mass measurements, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. During stability tests wherein the cross-linked fibers were exposed to three aqueous solutions, the cross-linked fibers were stable in water and acid buffer yet swelled in phosphate buffer saline, making them useful scaffolds for pH-controlled release applications. Proof-of-concept release experiments were conducted using a simulated gastrointestinal tract model. As desired, the cargo remained encapsulated within the cross-linked nanofibers when exposed to an acidic solution that modeled the stomach. Upon exposure to a solution that mimicked the intestines, the cargo was released. We suggest that these cross-linked, alginate-based nanofiber mats hold the potential to be broadly used in biomedical and environmental applications.

Magnetic chitosan/calcium alginate double-network hydrogel beads: Preparation, adsorption of anionic and cationic surfactants, and reuse in the removal of methylene blue

Robust and reusable magnetic chitosan/calcium alginate double-network hydrogel beads (CSMAB) with an environmentally benign biocomposite material synthesis approach were used adsorption of surfactant and removal of methylene blue dye sequentially for the first time. Double network hydrogel structure with sodium alginate and chitosan and acidification of the surface with HCl provided the reusability of the beads at the pollutant removal in water. The CSMAB beads were characterized for structural analysis by FESEM, EDX, BET, VSM, and FTIR techniques. They were used for the adsorption of cationic hexadecylpyridinium chloride (HDPCl) and anionic sodium dodecyl sulfate (SDS) surfactants and reused in the removal of cationic methylene blue dye without any pretreatment. The effect of pH, adsorbent dose, and temperature on surfactant removal efficiency was analyzed and pH was found the statistical significance. The adsorption capacity of CSMAB beads with a surface area of 0.65 m² g^-1 was calculated as 1.9 mg g^-1 for HDPCl, and 1.2 mg g^-1 for SDS, respectively. The SDS and HDPCl adsorption followed the pseudo-second-order kinetic and Freundlich isotherm model. The thermodynamic results showed that the surfactant adsorption process is an exothermic and spontaneous process. SDS-reacted CSMAB beads showed higher efficiency with 61 % in the removal of methylene blue dye.

Bioaccessibility assay, antioxidant activity and consumer-oriented sensory analysis of Beta vulgaris by-product encapsulated in Ca(II)-alginate beads for different foods

Bioaccessibility analysis and antioxidant activity along in vitro digestion and a consumer-oriented sensory analysis were conducted in three potential functional foods based on Ca(II)-alginate beads containing bioactive compounds extracted from beet stems. Ca(II)-alginate beads per se, and two selected products (cookies and turkish delights supplemented with the beads) were prepared. Regarding the beads, among the attributes rated by consumers, visual appreciation predominates, being color in the just-as-right (JAR) category and in the like preference. Instead, both flavor and sweet taste were attributes highly penalized and should be improved in beads to be accepted as food per se. A higher percentage of customers preferred cookies and turkish delights instead of only beads, considering global satisfaction. Regarding in vitro digestion, there was a significant content of phenolic compounds in the products with beads, showing a bioaccessibility greater than 80% (for cookies) and 26% (for turkish delights). Also, the antioxidant capacity measured by ABTS ranged between 50 and 109% for cookies and turkish delights, being lower when measured by FRAP (between 20 and 30%, respectively). Thus, including the beads with beet stem extract in both products leads to a significant increase in the content of phenolic compounds and in the antioxidant capacity compared to their counterparts, protecting the compound during oral and gastric phases. These results allow the generation of improved Ca(II)-alginate systems with promising functional properties for the development of ingredients and functional foods.

Optimization of Encapsulation by Ionic Gelation Technique of Cryoconcentrated Solution: A Response Surface Methodology and Evaluation of Physicochemical Characteristics Study

The objective of this study was to evaluate the optimal conditions to encapsulate cryoconcentrate solutions via ionic gelation technique. Hydrogel beads were prepared using alginate (1%, 2% and 3% (w/w)) and cornstarch (0.5%, 1% and 2% (w/w)). Later, a sucrose/acid gallic solution was concentrated through block freeze concentration (BFC) at three cycles. Thus, each solution was a mixture with the respective combination of alginate/cornstarch. The final solution was added drop-wise on a CaCl₂ solution, allowing the formation of calcium alginate-cornstarch hydrogel beads filled with sucrose/acid gallic solution or cryoconcentrated solution. The results showed that alginate at 2% (w/w) and cornstarch at 2% (w/w) had the best efficiency to encapsulate any solution, with values close to 63.3%, 90.2%, 97.7%, and 75.1%, and particle sizes of approximately 3.09, 2.82, 2.73, and 2.64 mm, for initial solution, cycle 1, cycle 2, and cycle 3, respectively. Moreover, all the samples presented spherical shape. Therefore, the appropriate content of alginate and cornstarch allows for increasing the amount of model cryoconcentrated solution inside of the hydrogel beads. Furthermore, the physicochemical and morphological characteristics of hydrogel beads can be focused for future food and/or pharmaceutical applications, utilizing juice or extract concentrated by BFC as the solution encapsulated.

Encapsulation of Lactobacillus gasseri: Characterization, Probiotic Survival, In Vitro Evaluation and Viability in Apple Juice

The development of functional foods containing probiotic bacteria has become increasingly relevant to improve and maintain health. However, this is often limited to dairy food matrices given the complexity involved in maintaining a stable system together with high microbial viability in matrices such as juices. The objective of this study was to develop and characterize sodium alginate capsules loaded with Lactobacillus gasseri ATCC® 19992 ™ (LG). Cell viability under in vitro gastrointestinal conditions and during storage in apple juice were evaluated. The capsules were prepared by ionic gelation and an emulsification process was performed as pretreatment using two homogenization methods: magnetic stirring (AM) and Ultraturrax® rotor-stator homogenizer (UT). Cell viability after encapsulation was similar in the two processes: 65%. At the end of the in vitro gastrointestinal evaluation, the non-encapsulated probiotic cells did not show any viability, while the AM system was able to retain 100% of its viability and the UT retained 79.14%. The morphology of the capsules consisted of a continuous and homogeneous surface. Cell viability of LG encapsulated in apple juice stored at 4 °C for 21 days was 77% for AM, 55.43% for UT, and 63.10% for free LG.

Encapsulation of Lacticaseibacillus rhamnosus GG: Probiotic Survival, In Vitro Digestion and Viability in Apple Juice and Yogurt

This study was aimed to prepare and characterize capsules loaded with Lacticaseibacillus rhamnosus GG (LGG), evaluating cell viability under gastrointestinal in vitro conditions and during storage in yogurt and apple juice, an alternative to traditional probiotic foods for people who are lactose intolerant. The capsules were prepared by ionic gelation, with an emulsification process as pretreatment. Cell viability of encapsulated LGG was evaluated after two different homogenization processes: magnetic stirring (AM) and Ultraturrax® homogenizer (UT). The system with the best relationship between viability and morphology was UT, which produced a viability of 85.80%. During in vitro evaluation, the capsules provided higher protection than free cells, up to 100% of cell viability. The morphology of capsules of both systems displayed a continuous and homogeneous surface. The cell viability of the encapsulated probiotics added in apple juice stored for 22 days at 4 °C was 86.16% for AM and 100% for UT, while the viability of free cells was 80.50%. In natural yogurt, the cell viability of the probiotics encapsulated stored 30 days at 4 °C was 100% for AM, 100% for UT, and 92.68% for free cells. This study suggests an alternative to preserve probiotic bacteria in a potential functional food.

Evaluation of calcium alginate bead formation kinetics: An integrated analysis through light microscopy, rheology and microstructural SAXS

Ca(II)-alginate beads are being produced for a broad spectrum of biotechnological uses. Despite the simplicity of their manufacturing process, in these highly complex arrangements, the final properties of the material strongly depend on the supramolecular scaffolding. Here we present a cost-effective automatized Optical Video Microscopy approach for in situ evaluation of the kinetics of alginate bead formation. With simple mathematic modeling of the acquired data, we obtained key parameters that reveal valuable information on the system: the time course of gel-front migration correlates with the plateau of the storage module, and total volume shrinkage is highly related to the stabilization of shear strain and shear stress at the yield point. Our results provide feasible and reproducible tools, which allow for a better interpretation of bead formation kinetics and a rapid screening technique to use while designing gelling materials with specific properties for technological applications.

Release of encapsulated bioactives influenced by alginate viscosity under in-vitro gastrointestinal model

The physicochemical properties of alginate can affect the release profile of encapsulated bioactives, but this is poorly understood. The influence of alginate viscosity (low- A1, medium- A2 and high- A3) and molecular weight (kDa) on the release of encapsulated bioactives (seaweed and spirulina powder) was investigated in an in-vitro gastrointestinal (GSI) model. Beads encapsulated with A2 at 1% (w/v) have overall higher release of bioactives (protein, phlorotannins and antioxidants) but A3 at 0.5% (w/v) was able to release and absorb similar amount of bioactives with ~10% difference with A2. The relative release of protein, phlorotannins and antioxidant was 96%, 111% and 43% respectively from A2 in gastric digestion. In contrast, protein (165%) and phlorotannins (234%) release was highest from A3 in intestinal phase. These results establish the importance of physicochemical properties of the encapsulating matrix on water retention capacity and their interaction with bioactive material to release into the system.

High-intensity ultrasound-assisted extraction of phenolic compounds from cowpea pods and its encapsulation in hydrogels

Currently and according to the growing worldwide interest in the revaluation of agricultural by-products, the use of legumes waste presents great potential to obtain bioactive compounds. In this context, an extract rich in phenolic compounds was obtained from Vigna unguiculata (cowpea) pods by optimizing the high-intensity ultrasound conditions (10 min and 36% of amplitude) using response surface methodology. Then, the extract was encapsulated in Ca(II)-alginate beads with the addition of arabic or guar gums or cowpea isolated proteins. A complete morphological study by image analysis and microstructural evaluation by SAXS has been carried out. Results showed that beads containing alginate and alginate-guar gum have the highest loading efficiency of total phenolic compounds (47 ± 5%) and antioxidant activity (44 ± 3%). However, the coupled effect of the cowpea extract and the isolated proteins (at it higher concentration) increased the antioxidant capacity of the beads due to the contribution of the phenolic compounds and the amino acids with anti-radical activity, reaching a value of 67 ± 3 % of inhibition of ABTS.+. Finally, the microstructural analyses revealed that cowpea pod extract increased the interconnectivity of the rods due to the presence of trivalent cations, conferring versatility, and larger coordination to the network. Also, it was observed that the addition of cowpea proteins produced more interconnected bigger and fewer compacts rods than beads containing only alginate, increasing 12 and 49 % the interconnection and the size, respectively, and decreasing 10 % their compactness. This research demonstrated the use of cowpea sub-products as a source of bioactive compounds that further modulate the microstructure of the hydrogel network, and the outstanding potential for being incorporated in techno-functional foods by using Ca(II)-alginate as a carrier.

Evaluation of sodium alginate for encapsulation-vitrification of testicular Leydig cells

This study reports encapsulation-vitrification of Leydig cells. The Leydig cells were encapsulated in sodium alginate beads of different sizes and cryopreserved by vitrification or slow freezing. Physico-chemical characterization of beads was done by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Fluorescence Recovery after Photobleaching (FRAP) and in vitro biodegradation study. Surface morphology of cryopreserved cell-encapsulated beads was evaluated by Environmental Scanning Electron Microscopy (E-SEM), encapsulation efficiency and viability of cells were assessed by Trypan blue assay, mitochondrial activity (MTT assay) and cytoplasmic esterase enzyme activity (FDA assay), respectively. Results showed that vitrification gives better results than slow freezing with respect to surface morphology as well as cell viability of the cell-encapsulated beads (86.94 ± 2.20% vs. 67.94 ± 2.30%; p < 0.05). Encapsulation of cells in small diameter beads (1.8 mm) gave a better cell proliferation rate than large (2.1 mm and 2.7 mm). There was a significant difference in the population doubling time (47.9 ± 1.7 h vs. 67.1 ± 2.5 h) and cell proliferation rate (0.50 ± 0.24 vs. 0.36 ± 0.24 per day) of vitrified-warmed cell encapsulated beads with different diameter (p < 0.05). Encapsualtion in sodium alginate beads is a promising method for cryopreservation of Leydig cells by slow freezing as well as vitrification.

Egg-box model-based gelation of alginate and pectin: A review

Alginate and pectin are emblematic natural polyuronates that have been widely used in food, cosmetics and medicine. Ca-dependent gelation is one of their most important functional properties. The gelation mechanisms of alginate and pectin, known as egg-box model, were believed to be basically the same, because their Ca-binding sites show a mirror symmetric conformation. However, studies have found that the formation and the structure of egg-box dimmers between alginate and pectin were different. Very few studies have reviewed those differences. Therefore, this study was proposed to first summarize the intrinsic and extrinsic factors that can influence the gelation of alginate and pectin. The differences in the effect of these factors on the gelation of alginate and pectin were then discussed. Meanwhile, the similarity and difference in their gelation mechanism was also summarized. The knowledge gained in this review would provide useful information for the practical applications of alginate and pectin.

Structure-rheology relationships of composite gels: Alginate and Basil seed gum/guar gum

Structure-rheology relationship of binary composite gel (BCG) systems of alginate/guar gum and basil seed gum/guar gum at ratio 2:1 at different Ca²⁺ levels (2-10%) were evaluated. The highest value of structural strength was obtained at 2 % of Ca²⁺, which can be attributed to its stronger network as assessed by rheological experiments. Mechanical spectra of the alginate/guar gels explained pseudoplastic behavior with a highly interconnected elastic gel structure. The mechanical strength as well as other textural properties of the alginate and basil seed gum network was functions of its stoichiometry with calcium ions. Whereas alginate/guar gels showed an elongated globular denser structure as determined by SEM, the BSG/guar gels showed a rigid cubic as the pieces of a puzzle, presenting a softer and weaker gel structure. The alginate/guar gels showed less porosity without syneresis or shrinkage during storage as supported by its high elasticity and rigidity.