Alginate Complex Research Articles

Ion-Induced Polysaccharide Gelation: Peculiarities of Alginate Egg-Box Association with Different Divalent Cations.

Structural aspects of polysaccharide hydrogels based on sodium alginate and divalent cations Ba2+, Ca2+, Sr2+, Cu2+, Zn2+, Ni2+ and Mn2+ was studied using data on hydrogel elemental composition and combinatorial analysis of the primary structure of alginate chains. It was shown that the elemental composition of hydrogels in the form of freezing dried microspheres gives information on the structure of junction zones in the polysaccharide hydrogel network, the degree of filling of egg-box cells by cations, the type and magnitude of the interaction of cations with alginate chains, the most preferred types of alginate egg-box cells for cation binding and the nature of alginate dimers binding in junction zones. It was ascertained that metal-alginate complexes have more complicated organization than was previously desired. It was revealed that in metal-alginate hydrogels, the number of cations of various metals per C12 block may be less than the limiting theoretical value equal to 1 for completely filled cells. In the case of alkaline earth metals and zinc, this number is equal to 0.3 for calcium, 0.6 for barium and zinc and 0.65-0.7 for strontium. We have determined that in the presence of transition metals copper, nickel and manganese, a structure similar to an egg-box is formed with completely filled cells. It was determined that in nickel-alginate and copper-alginate microspheres, the cross-linking of alginate chains and formation of ordered egg-box structures with completely filled cells are carried out by hydrated metal complexes with complicated composition. It was found that an additional characteristic of complex formation with manganese cations is the partial destruction of alginate chains. It has been established that the existence of unequal binding sites of metal ions with alginate chains can lead to the appearance of ordered secondary structures due to the physical sorption of metal ions and their compounds from the environment. It was shown that hydrogels based on calcium alginate are most promising for absorbent engineering in environmental and other modern technologies.

Cruciferin improves stress resistance and simulated gastrointestinal survival of probiotic Limosilactobacillus reuteri in the model encapsulation system

Encapsulation is a viable strategy to improve the stability and survival of probiotics during processing, storage, and consumption. Cruciferin, a major canola protein with high denaturation temperature and resistance to gastric degradation, has potential for encapsulation and protection of probiotics against harsh conditions in processing and gastrointestinal tract. Cruciferin/alginate capsules were fabricated to encapsulate probiotics, and were characterized using confocal and scanning electron microscopy (SEM). The bacterial viability was studied during storage, processing, and gastro-intestinal transit. Limosilactobacillus reuteri TMW 1.656 was encapsulated in spherical cruciferin/alginate capsules (2.2 ± 0.1 mm) prepared using an extrusion method. SEM images of the capsules showed that the bacteria were entrapped within the porous structure which was formed by the complexation of cruciferin and alginate. The confocal microscopy images confirmed that cruciferin and alginate were homogeneously distributed throughout the capsules. The shelf life of the bacteria in the presence of cruciferin and alginate increased up to 8 weeks at 4 °C, while unencapsulated (free) bacteria lost their viability after 2 weeks storage. The heat resistance of encapsulated bacteria exposed to 65 °C and 70 °C was improved by up to ∼ 4 and 2 log cycles, respectively, compared to unencapsulated bacteria. Encapsulation also protected L. reuteri against gastric low pH and enzymes; the viability was 3 logs higher when compared to unencapsulated bacteria. The capsules were degraded in simulated intestinal fluid, leading to the release of the encapsulated bacteria, whereas the wall materials increased the resistance of released bacteria to bile salts. Comparison between the viability of unencapsulated bacteria in presence of cruciferin/alginate mixtures and bacteria encapsulated in the capsules revealed that capsule formation provided physical barriers to the harsh conditions and played a key role in the protection of bacteria. This study showed that cruciferin/alginate capsules are capable to improve stability and shelf life of Limosilactobacillus reuteri.

Tunable chitosan-alginate capsules for a controlled release of crystallisation inhibitors in mortars

Plasters and renders used in historic monuments are vulnerable to degradation caused by salt weathering. Crystallisation inhibitors (molecules/ions that alter salt crystallisation) mixed into mortars have shown promising results in mitigating salt damage by inhibiting salt crystallisation, promoting salt transport to the evaporating surface, and modifying crystal habit. However, past research suggests that inhibitors easily leach out from mortars, meaning their long-term positive effect is lost. Encapsulation of an inhibitor within a mortar is a potential solution to minimise leaching. Herein, capsules composed of a polyelectrolyte complex of calcium alginate coated in chitosan are investigated for the controlled diffusive release of sodium ferrocyanide, a known NaCl crystallisation inhibitor. Capsules with varying chitosan-calcium alginate ratios are prepared using the extrusion dripping technique. The release of the inhibitor from capsules in solutions of various pH values ranging from 7–13 is investigated. Results show that increasing the capsule’s chitosan to calcium alginate ratio reduces the inhibitor release for all studied solution pH values compared to pure calcium-alginate capsules. Therefore, a controlled inhibitor release can be obtained by tuning the chitosan-alginate ratio. In future, additional tests will be performed to find suitable capsule compositions for optimising their performance when mixed in mortars.

Microencapsulation of Rose Essential Oil Using Perilla Protein Isolate-Sodium Alginate Complex Coacervates and Application of Microcapsules to Preserve Ground Beef

Microencapsulation of Rose Essential Oil Using Perilla Protein Isolate-Sodium Alginate Complex Coacervates and Application of Microcapsules to Preserve Ground Beef

Interaction and phase behavior of whey protein and propylene glycol alginate complex condensates

Whey protein (WP) is ubiquitously applied in food products, but its sensitivity to food processing conditions has limited its application. Herein, we chose propylene glycol alginate (PGA) to combine with WP to enhance its stability. The ideal ratio of WP/PGA for coacervation was 3:1, and the soluble complex and insoluble complex were formed at pH 5.2 (pHc) and pH 4.4 (pHφ1) at this ratio, respectively. The UV absorption spectra, fluorescence spectra, and XRD results revealed that the interaction between PGA and WP changed the tertiary conformation of WP. The FTIR and molecular docking results suggested electrostatic interactions, hydrogen bonding and hydrophobic interactions were all involved in the formation of WP-PGA complexes, and the thermal stability of WP was improved based on the DSC results. These findings supported PGA to keep dairy products stable and transparent at the isoelectric point and WP-PGA complexes could be applied in encapsulating bioactive substances.

Physicochemical properties and formation mechanism of whey protein isolate-sodium alginate complexes: Experimental and computational study

The study explored the interaction mechanism between whey protein isolate and polysaccharide at the molecular level. Firstly, the effect of pH on the formation of whey protein isolate-sodium alginate complex was investigated. The particle size and turbidity were reduced in the presence of sodium alginate over a wide pH range. They were remarkably decreased (by 65% and 68.5%, respectively) at pH 5.0 (near the isoelectric point), which was confirmed by fluorescence microscopy. Raman spectroscopy results showed that the presence of sodium alginate resulted in more compact structure (α-helix content increased by 7.53% at pH 5.0) of whey protein isolate at pH 5.0. Then, the interaction and formation mechanism of the complex at the molecular level were explored by computational approaches. Molecular docking study showed that the amino acid residues of β-lactoglobulin formed a complex with –COOH and –OH of sodium alginate. Molecular dynamics simulation analysis illustrated that the binding energy (−338.17 kJ/mol) of the complex was relatively low at pH 5.0, indicating that β-lactoglobulin and sodium alginate had relatively strong binding capacity and stability. Electrostatic interactions which belong to non-bonding contribution played a major role in the formation of β-lactoglobulin-sodium alginate complex. This study provided theoretical basis for further research on the interactions between protein and polysaccharide, improving the stability of protein in acidic food. • Alginate inhibited the aggregation of whey protein isolate near the isoelectric point. • Spectroscopic and molecular dynamics simulation approaches were used. • Relatively strong binding of sodium alginate to whey protein at pH 5.0 • Electrostatic forces dominated the binding of sodium alginate to whey protein isolate.

Microencapsulation of Bacteriophages for the Delivery to and Modulation of the Human Gut Microbiota through Milk and Cereal Products

There is a bidirectional interaction between the gut microbiota and human health status. Disturbance of the microbiota increases the risk of pathogen infections and other diseases. The use of bacteriophages as antibacterial therapy or prophylaxis is intended to counteract intestinal disorders. To deliver bacteriophages unharmed into the gut, they must be protected from acidic conditions in the stomach. Therefore, an encapsulation method based on in situ complexation of alginate (2%), calcium ions (0.5%), and milk proteins (1%) by spray drying was investigated. Powdered capsules with particle sizes of ~10 µm and bacteriophage K5 titers of ~107 plaque-forming units (pfu) g−1 were obtained. They protected the bacteriophages from acid (pH 2.5) in the stomach for 2 h and released them within 30 min under intestinal conditions (in vitro). There was no loss of viability during storage over two months (4 °C). Instead of consuming bacteriophage capsules in pure form (i.e., as powder/tablets), they could be inserted into food matrices, as exemplary shown in this study using cereal cookies as a semi-solid food matrix. By consuming bacteriophages in combination with probiotic organisms (e.g., via yoghurt with cereal cookies), probiotics could directly repopulate the niches generated by bacteriophages and, thus, contribute to a healthier life.

PH-driven self-assembly of alcohol-free curcumin-loaded zein-propylene glycol alginate complex nanoparticles

This study aimed to prepare alcohol-free curcumin-loaded zein-propylene glycol alginate (zein-PGA-Cur) nanoparticles using the pH-driven method to enhance the bioavailability and physicochemical stability of curcumin. The prepared zein-PGA-Cur nanoparticles exhibited a small size (360 nm) and negative zeta-potential (−5.8 mV), as well as excellent physical stability, under storage conditions of pH 4.0 and temperature at 4 °C for 30 days. In addition, the Fourier transform infrared spectroscopy results demonstrated that the main interactions of pH-driven for the formation of zein-PGA-Cur nanoparticles were hydrogen bonding, hydrophobic, and electrostatic interactions. Fluorescence spectroscopy revealed that the curcumin-induced fluorescence quenching of zein was static. Circular Dichroism spectroscopy demonstrated that the pH-driven method mainly decreased the β-sheet structure of zein from 3.9 % to 1.4 %. Furthermore, the HT-29 colorectal adenocarcinoma cells viability experiments revealed that the prepared zein-PGA-Cur nanoparticles exhibited excellent biocompatibility. In vivo rat experiments also demonstrated that the prepared nanoparticles resulted in a higher plasma concentration of curcumin, representing a 7.2-fold enhancement in bioavailability compared with pure curcumin crystals. The findings of this study will provide a green and energy-saving method for the development of insoluble drug self-assembly systems and promote their wider applications in drug delivery.

Loadings of lycopene in emulsion and sodium alginate-K-carrageenan composite systems: Preparation, characterization, bioaccessibility, and kinetics.

This research aims to prepare capsules emulsion using gallic acid (GA), dextran (DEX), bovine serum albumin (BSA), sodium alginate, and K-carrageenan (K-Car) as the biological delivery system of lycopene. The stability and bioaccessibility of lycopene were further improved through encapsulation of covalent complex of sodium alginate and K-Car. The molecular weight distribution and secondary structure of the conjugates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR). The storage stability of the emulsion stabilized by conjugates was measured with Turbiscan stability index (TSI) and fluctuation of the particle size. The TSI value of ternary conjugates was 18.7 (37℃) with particle sizes ranging from 208 to 319nm. Then, the changes of three-dimensional reticulate structures and physical properties of sodium alginate-K were analyzed by scanning electron microscopy (SEM) and TPA. The thermal stability of the sodium alginate-K-Car composite systems was increased compared with sodium alginate. The bioaccessibility of lycopene was significantly improved under the dual embedding of BSA-DEX-GA conjugate emulsion and sodium alginate-K-Car composite systems.

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

An emulsion delivery system for benzyl isothiocyanate (BITC) was prepared using fish skin gelatin (FSG) and sodium alginate (Alg). The effects of the FSG-Alg complex on the emulsion stability and BITC release pattern from the emulsion were investigated in vitro and in vivo. The storage stability and embedding rate of the 10g kg-1 FSG and 2.5g kg-1 Alg (FSG-Alg) emulsion were the highest among all samples. The FSG-Alg complex provided BITC a better protection during in vitro digestion. The microstructure of the FSG-Alg emulsions was more stable during in vitro digestion, and the bioaccessibility and retention rate of BITC were much higher compared to those of the FSG emulsion. The results of the ex vivo everted gut sac of rat intestine study showed that the FSG-Alg emulsion significantly increased the BITC absorption rate in the duodenum. The FSG-Alg emulsion delivery system is a highly stable system for the delivery of BITC that improves the bioaccessibility of BITC and promotes its absorption in the duodenum. © 2022 Society of Chemical Industry.

Structural Effects of pH Variation and Calcium Amount on the Microencapsulation of Glutathione in Alginate Polymers.

Reduced glutathione (GSH) has a high antioxidant capacity and is present in nearly every cell in the body, playing important roles in nutrient metabolism, antioxidant defense, and regulation of cellular events. Conversely, alginate is a macromolecule that has been widely used in the food, pharmaceutical, biomedical, and textile industries due to its biocompatibility, biodegradability, nontoxicity, and nonimmunogenicity as well as for its capabilities of retaining water and stabilizing emulsions. The primary goal of this study was to characterize and optimize the formation of a molecular complex of calcium alginate with GSH using a computational approach. As methods, we evaluated the influence of varying the amount of calcium cations at two different pHs on the structural stability of Ca2+-alginate complexes and thus on GSH liberation from these types of nanostructures. The results showed that complex stabilization depends on pH, with the system having a lower Ca2+ amount that produces the major GSH release. The systems at pH 2.5 retain more molecules within the calcium-alginate complex, which release GSH more slowly when embedded in more acidic media. In conclusions, this study demonstrates the dependence of the amount of calcium and the stabilizing effect of pH on the formation and subsequent maintenance of an alginate nanostructure. The results presented in this study can help to develop better methodological frameworks in industries where the release or capture of compounds, such as GSH in this case, depends on the conditions of the alginate nanoparticle.

Transglutaminase Cross-Linking of Whey Proteins Affects Alginate Complexation

Transglutaminase Cross-Linking of Whey Proteins Affects Alginate Complexation

Simulated gastrointestinal digestion of protein alginate complexes: effects of whey protein cross-linking and the composition and degradation of alginate.

Alginate and whey protein are common additives in food production improving storage stability, texture and nutritional value. Alginate forms complexes with whey protein and inhibits proteolysis by pepsin and trypsin, but the influence of alginate protein complexation on digestion is poorly understood. This study shows that whey protein cross-linking by microbial transglutaminase dramatically decreased particle size (2-fold) and viscosity of alginate protein complexes. The INFOGEST in vitro simulated gastrointestinal digestion of whey protein was increased by cross-linking (16%) and suppressed by alginate, most pronounced with high mannuronic acid and least with high guluronic acid content. Sizes of alginate whey protein particles increased during gastric digestion, whereas for cross-linked whey protein complexes the size initially increased, but returned to their initial size at the end of gastric digestion. While alginate is not degraded by human enzymes, a few gut bacteria were recently found to encode lyases and other enzymes metabolizing alginate. Alginate lyase added to the intestinal phase enhanced digestion (9%) as controlled by alginate composition and enzyme specificity. Thus we provide evidence that use of hydrocolloids and processing of protein strongly influence digestion and should be considered when using food additives.

A DFT study on Ca-Alginate interactions with divalent transition metals

Alginate is a naturally occurring linear polysaccharide that is extracted from brown algae. This is generally produced as water-soluble Na alginate which in turn is transformed into water-insoluble Ca-Alginate beads. These beads are potential adsorbents for the removal of heavy metal ions from water through ion exchange with calcium ions present in the Ca-Alginate matrix. To investigate the feasibility of ion exchange of various heavy metal ions, Density Functional Theory (DFT) calculations were carried out using the Gaussian-16 simulation package. The heavy transition metal ions with + 2 valence in the 4th, 5th, and 6th periods of d-block were considered for the study as most of the heavy metals (e.g., Cu, Cr, Ni, Co, Mn, etc.) are present in this block and significantly contribute to water pollution. The widely accepted egg-box molecular model representation of alginate structures is used for computation purposes. For computation purposes, one monomer attached from top and bottom to the metal center is considered. The computations were carried out in both vapor and aqueous solvent phases and the trends of binding energy were found to be invariant. The binding energies of the alginate complexes formed with Ni, Pd, and Pt metal ions of the 4th, 5th, and 6th series were the highest amongst all the metals considered in this work.

The improvement of the physicochemical properties and bioaccessibility of lutein microparticles by electrostatic complexation

In this study, biopolymer microparticles were fabricated for the encapsulation and delivery of lutein by electrostatic complexation of sodium caseinate (NaCas) and sodium alginate (ALG) to improve its physicochemical stability and bioaccessibility. The lutein microparticles were determined by analysis of the particle size, zeta-potential, physical stability and microstructure. The formation mechanism of lutein microparticles was examined by Fourier transform infrared spectroscopy (FTIR) analysis. Moreover, the crystalline structure change of lutein was characterized by X-ray diffraction (XRD) and Differential scanning calorimetry (DSC). Bioaccessibility of lutein was also investigated in a simulated gastrointestinal tract (GIT) model. Lutein microparticles were rough irregular structures with larger mean particle size of 1750 ± 2.24 nm, higher physical stability and negative zeta-potential (−54.03 ± 0.38 mV) when the optimized concentration of NaCas and ALG were 2.0 wt%, respectively. FTIR analysis indicated the electrostatic interaction between the amino group of the caseinate and the carboxyl group of the alginate in the formation of microparticles. XRD and DSC analysis confirmed that lutein was encapsulated in microparticles as an amorphous state. Meanwhile, the microparticles effectively reduced the decomposition of lutein during 22 d storage at 37 °C. GIT studies showed that the microparticles presented higher free fatty acid (FFA) release and lutein bioaccessibility (51.27 ± 0.78%) than emulsions (12.83 ± 1.43%). This study provided a broad prospect for the formulation of lutein-fortified functional foods and beverages.

Preparation of iron-loaded water-in-oil-in-water (W1/O/W2) double emulsions: optimization using response surface methodology

Iron deficiency anemia is a major public health problem caused by low iron intake or bioavailability. To overcome the problem of anemia, iron fortification of a variety of food products is being tested worldwide. Ferric sodium EDTA is a desirable iron source for food fortification due to its high bioavailability and ability to prevent binding of iron to phytates during absorption. This study investigated the application of double emulsions for encapsulation and controlled delivery of ferric sodium EDTA stabilized by the lipophilic Span®80 and hydrophilic complex of sodium alginate and sodium caseinate emulsifiers. The influence of factors such as the ratio of internal water to the oil phase, concentrations of alginate or Span®80 and the ratio of water-in-oil emulsion to the external water on internal (din ) and external emulsion droplet sizes (dout ) was studied by response surface methodology. The feasible range for selection of factors for achieving target values of din and dout was proposed by the response optimizer confirmed by the results of experiments. The results indicate that double emulsion systems may be useful for iron fortification of food products.

Development, Physical-Chemical Characterization, and Molecular Docking Simulations of Ursolic Acid-Sodium Alginate Complexes.

The aim of this study was to fabricate ursolic acid (UA)-sodium alginate (SA) complexes to improve the dissolution rate and antioxidant abilities. The antioxidant activity was evaluated by the DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) assay and the pyrogallol auto-oxidation method. For the optimal composition ratio of UA:SA (1:5, w/w), the cumulative release of UA was about 101.22 ± 1.50% for 180 min. Powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analyses confirmed that the crystallinity of UA was significantly reduced by forming complexes with SA. By Fourier transform infrared spectroscopy (FTIR) and molecular docking simulations, it was observed that the hydroxyl group in UA formed hydrogen bonding with the carbonyl group in SA. The DPPH scavenger activities of the complexes were also increased compared with free UA. The results indicated that SA could serve as a promising carrier for lipophilic functional food ingredients due to improved solubility and antioxidant activity.

Fabrication of chitosan–alginate nanospheres for controlled release of cartap hydrochloride

Insecticide cartap hydrochloride (C) was fabricated as nanospheres by a two-step method of ionic gelification and polyelectrolyte complexation of alginate (ALG) and chitosan (CS) to undermine its adverse effects on environment. Nanospheres were characterized by field emission scanning electron microscope, Fourier transform infrared spectra and x-ray diffraction. The size of cartap hydrochloride entrapped chitosan alginate nanospheres (C-CS-ALG nps) was in range of 107.58–173.07 nm. Cartap hydrochloride nanospheres showed encapsulation efficiency of 76.19% and were stable for 30 d at ambient temperature. Release of cartap from nanospheres fitted best with first order linear kinetics followed by Hixson and Higuchi model suggesting super case II transport release. With the application of such control release nanoformulations, it is possible to reduce the frequency of field application of insecticide due to its slow release to the target organism, which is economical as well as environmentally safe.

A Study of Compressibility, Compactability and Mucoadhesivity of Tableting Materials for Matrix Systems Based on Chitosan.

The objective of the present research is to evaluate directly compressible chitosan-based tableting materials for the formulation of mucoadhesive matrix tablets intended for targeted drug release to distal segments of the GIT. The influence of sodium alginate, hypromellose, and silicified microcrystalline cellulose (P90) on compressibility, compactability and lubricant sensitivity ratio was tested. Furthermore, the rheological properties of the hydrated surface layer of the matrix tablets and the mucoadhesion to a mucin substrate were analysed. Compressibility was evaluated using the energy profile of the compression process, compactability by means of the tensile strength of tablets, and lubricant sensitivity ratio was calculated to assess the sensitivity to lubricant. Addition of P90 to chitosan improved compressibility, which is demonstrated by the increase in the energy of plastic deformation and the higher tensile strength of tablets. P90 also significantly reduced the high lubricant sensitivity of chitosan. Presence of retarding components led to a decrease in Emax. All tested matrix tablets revealed a good mucoadhesion without a negative effect of P90 content. The viscosity of a gel layer on the surface of matrix tablets containing hypromellose was higher compared to those with sodium alginate. This was not reflected in the adhesive strength of the tablets. The formulated tableting materials combining chitosan and P90 are a suitable matrix for incorporation of an active ingredient, whose delayed release in the intestine can be achieved by the functionality of the chitosan-sodium alginate complex.

Desalination of duck egg white by biocoagulation to obtain peptide-ferrous chelate as iron delivery system: Preparation, characterization, and Fe2+ release evaluation in vitro.

The annual output of salted duck egg white (SDEW) is estimated to be over 1.5 million tons in China, most of which is discarded due to high salt content. This has led to serious waste and environmental impact. Therefore, we developed an eco-friendly biocoagulation separation technology by combining chitosan and sodium alginate in order to produce a novel iron-binding peptide (DPs-Fe2+) from SDEW. The structure of DPs-Fe2+ was characterized by ultraviolet-visible spectroscopy, fluorescence spectroscopy, and Fourier transform infrared spectroscopy, followed by measuring DPs-Fe2+ response in a simulated digestion/Caco-2 cell model. Results showed that chitosan and sodium alginate complex could remove 91.21% of salt from SDEW, and the protein recovery rate reached 95.50%. Characterization results indicated that DPs bonded with Fe2+ to form a soluble chelate. Moreover, Caco-2 cell monolayer model indicated that the transport rate of Fe2+ was as high as 10.02% at 0.1mg/ml concentration of digested chelates. The results demonstrate the potential application of DPs as a novel carrier for enhancing iron absorption. This research contributes to the development of an effective industrial desalination method and highlights an opportunity for recycling an otherwise discarded processing byproduct. PRACTICAL APPLICATION: Salted duck egg whites (SDEW) are the primary byproduct of salted egg yolk production, most of which is discarded due to high salt content. Hence, efficient utilization of the high-value proteins in SDEW is an urgent problem that must be resolved. Herein, we developed an effective industrial desalination method by combining chitosan and sodium alginate, which achieved excellent SDEW desalination and protein recovery. Furthermore, we produced a novel iron-binding peptide (DPs-Fe2+), which enhanced the transportation and absorption of Fe2+ in Caco-2 cell model, suggesting its potential as an iron supplement.