Complex Coacervation of Milk Proteins with Sodium Alginate

Alginate binding enhances the structural stability and potentiates the lytic activity of bacteriophage endolysin's partially folded conformation

Polysaccharide polymers are increasingly being used as chaperon-like macromolecules in assisting protein folding of unfolded protein molecules. They interact with unfolded or partially folded proteins in a charge and conformation specific manner that results in the formation of stable protein-polysaccharide complexes. In most of the cases, the complex formation of protein-polysaccharide is driven via non-covalent interactions that have found to endorse the activity of proteins. T4L (18.7 kDa) and T7L (17 kDa) endolysins belong to the hydrolase and amidase class of peptidoglycan degrading enzymes. Both T4L and T7L exist in partially folded forms and are devoid of lytic activity at low pH conditions. In the current study, we assessed the binding of alginate with T4L and T7L at pH 7 and 3 using variety of biophysical and biochemical techniques. Spectroscopic studies revealed differential structural modulations of partially folded T4L and T7L upon their interaction with alginate. Further, the complex formation of alginate with partially folded T4L/T7L was confirmed by ITC and STEM. Additionally, the formed complexes of alginate with both T4L/T7L PF endolysins were found to be chemically and enzymatically stable. Moreover, such complexes were also marked with differential enhancement in their lytic activities at acidic pH conditions. This implied the potency of alginate as an excellent choice of matrix to preserve the structural and functional integrity of partially folded forms of T4L and T7L at highly acidic conditions.

Hazelnut Protein and Sodium Alginate Complex Coacervates: An Effective Tool for the Encapsulation of the Hydrophobic Polyphenol Quercetin

For valorization purposes of hazelnut byproducts, complex coacervation of hazelnut protein isolate (HPI) with sodium alginate (NaAlg) was investigated by turbidimetric analysis and zeta potential determination as a function of pH and protein/alginate mixing ratio. HPI-NaAlg complex coacervates were used as an encapsulating material of quercetin (QE) at different concentrations. The optimal pH and mixing ratio resulting in the highest turbidity and neutral charge were 3.5 and 6:1, respectively. The coacervation yield was 74.9% in empty capsules and up to 90.0% in the presence of QE. Under optimal conditions, HPI-NaAlg complex coacervates achieved an encapsulation efficiency higher than 99% in all coacervate/QE formulations. Fourier transform infrared spectroscopy (FTIR) results revealed the occurrence of electrostatic interactions between different functional groups within the ternary complex in addition to hydrogen and hydrophobic interactions between QE and HPI. HPI-NaAlg complex coacervates can serve as an alternative matrix for the microencapsulation of bioactive ingredients with low water solubility in food formulations, which adds an additional valorization of hazelnut byproducts.

Ratiometric Fluorescence Detection of Levofloxacin Based on a Cube-like Zn(II)-Eu(III) Nanocluster: Functionalized Sodium Alginate Film for the Detection in Serum and Medicine

A cube-like Zn(II)-Eu(III) nanocluster 1 (molecular sizes: 1.8 × 2.0 × 2.0 nm) was constructed by the use of a new long-chain Schiff base ligand. It shows a ratiometric fluorescence response to levofloxacin (LFX) with high sensitivity and selectivity, which can be expressed as I615 nm/I550 nm = A*[LFX]2 + B*[LFX] + C. It is used to quantitatively detect the LFX concentrations in fetal calf serum (FCS) and tablets sold in pharmacy. Filter paper strips bearing 1 can be used to qualitatively detect LFX by a color change to red under a UV lamp. 1 and its hybrid with sodium alginate (SA), 1@SA, display potential applications in the qualitative detection of LFX in FCS and the medicine. The limit of detection of 1 to LFX is as low as 2.1 × 10-2 nM.

Microencapsulation of Essential Oils Using Faba Bean Protein and Chia Seed Polysaccharides via Complex Coacervation Method

The aim of this study was to develop microcapsules containing juniper or black pepper essential oils, using a combination of faba bean protein and chia seed polysaccharides (in ratios of 1:1, 1:2, 2:1). By synergizing these two polymers, our goal was to enhance the efficiency of essential oil microencapsulation, opening up various applications in the food industry. Additionally, we aimed to investigate the influence of different polymer mixing ratios on the properties of the resulting microcapsules and the course of the complex coacervation process. To dissolve the essential oils and limit their evaporation, soybean and rapeseed oils were used. The powders resulting from the freeze-drying of coacervates underwent testing to assess microencapsulation efficiency (65.64-87.85%), density, flowability, water content, solubility, and hygroscopicity. Additionally, FT-IR and DSC analyses were conducted. FT-IR analysis confirmed the interactions between the components of the microcapsules, and these interactions were reflected in their high thermal resistance, especially at a protein-to-polysaccharide ratio of 2:1 (177.2 °C). The water content in the obtained powders was low (3.72-7.65%), but it contributed to their hygroscopicity (40.40-76.98%).

Microencapsulation of green coffee oil by complex coacervation of soy protein isolate, sodium casinate and polysaccharides: Physicochemical properties, structural characterisation, and oxidation stability

This study developed a combination method between protein-polysaccharide complex coacervation and freezing drying for the preparation of green coffee oil (GCO) encapsulated powders. Different combinations of soy protein isolate, sodium caseinate, sodium carboxymethylcellulose, and sodium alginate were utilised as wall materials. The occurrence of complexation between the biopolymers were compared to the final emulsion of the individual protein and confirmed by fourier transform infrared spectrometry and X-ray diffraction. The mean diameter and estimated PDI of GCO microcapsules were 72.57-295.00 μm and 1.47-2.02, respectively. Furthermore, the encapsulation efficiency of GCO microcapsules was between 61.47 and 90.01 %. Finally, oxidation kinetics models of GCO and its microcapsules demonstrated that the zero-order model of GCO microcapsules was found to have a higher fit, which could better reflect the quality changes of GCO microcapsules during storage. Different combinations of proteins and polysaccharides exhibited effective oxidative stability against single proteins because of polysaccharide addition. This research revealed that soy protein isolate, sodium caseinate combined with polysaccharides can be used as a promising microencapsulating agent for microencapsulation of GCO, especially with sodium carboxymethylcellulose and sodium alginate, and provided useful information for the potential use of GCO in the development of powder food.

Formation and microstructural characterization of scallop (Patinopecten yessoensis) male gonad hydrolysates/sodium alginate coacervations as a function of pH

Studying the noncovalent interactions between proteins and polysaccharides is quite important mainly due to the wide number of applications such as developing pH-responsive complexes. Scallop Patinopecten yessoensis male gonad hydrolysates‑sodium alginate (SMGHs-SA) was investigated as noncovalent complexes at pH from 1 to 10. The critical pH values pHC (around 6) and pHφ (around 4) were independent of the SMGHs-SA ratio, indicating the formation of soluble and insoluble complexes. The pH response of SMGHs-SA complexes was evaluated by investigating the rheological behavior, moisture distribution, functional group change and microstructure. Compared to the co-soluble and soluble complexes phases, the SMGHs-SA complexes had a higher storage modulus and viscosity as well as a lower relaxation time (T23) in the insoluble complexes phase (pHφ>3). Additionally, the amide I band and COO- stretching vibration peaks were redshifted and the amide A band vibration peaks were blueshifted by acidification. Electrostatic interactions and intermolecular/intramolecular hydrogen bonding led to SMGHs-SA agglomeration at pH 3, forming a uniform and dense gel network structure with strong gel strength and water-retention capacity. This study provides a theoretical and methodological basis for the design of novel pH-responsive complexes by studying SMGHs-SA complex coacervation.

Fabrication and Characterization of Complex Coacervation: The Integration of Sesame Protein Isolate-Polysaccharides

The exceptional biocompatibility of emulsion systems that rely on stabilizing protein-polysaccharide particles presents extensive possibilities for the transportation of bioactive carriers, making them highly promising for various biological applications. The current work aimed to explore the phenomenon of complex coacervation between sesame protein isolate (SPI) and four distinct polysaccharides, namely, Arabic gum (GA), carrageenan (CAR), sodium carboxymethyl cellulose (CMC), and sodium alginate (SA). The study objective was achieved by fabricating emulsions through the blending of these polymers with oil at their maximum turbidity level (φ = 0.6), followed by the measurement of their rheological properties. The turbidity, ζ-potential, and particle size were among the techno-parameters analyzed to assess the emulsion stability. The microstructural characterization of the emulsions was conducted using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Furthermore, the functional properties were examined using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The SPI incorporated with SA, CMC, and CAR reached the maximum turbidity (0.2% w/v) at a ratio of 4:1, corresponding to the pH values of 4.5, 3, or 3.5, respectively. The SPI-GA mixture exhibited the maximum turbidity at a ratio of 10:1 and pH 4.5. Results from the FTIR and XRD analyses provided evidence of complex formation between SPI and the four polysaccharides, with the electrostatic and hydrogen bond interactions facilitating the binding of SPI to these polysaccharides. SPI was bound to the four polysaccharides through electrostatic and hydrogen bond interactions. The SPI-CMC and SPI-SA emulsions were more stable after two weeks of storage.

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.

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.

Tuning alginate β-lactoglobulin complex coacervation by modulating pH and temperature

The use of biomolecules in food matrices and encapsulation systems is, as in other areas, moving towards greener solutions and a center piece here is the complex coacervation between natural anionic polysaccharides and proteins. Both alginate and β-lactoglobulin (β-Lg) are used in different sectors and have been shown to coacervate at pH < 5.2. Albeit with increased interest, complex coacervation has almost exclusively been studied from a macromolecular perspective, and described as an interaction based on charge-charge attraction. Here, we show that through changes in pH and temperature, alginate β-Lg complex coacervation can be tuned to purpose. By detailed biophysical and chemical characterization of coacervation and coacervate particles, insights into the molecular interaction and effect of external factors are obtained. We find that carboxylate resonance stabilization causes a release of protons at pH < pK_a,alginate and an uptake of protons at pH > pK_a,alginate upon coacervation. Proton release and uptake were quantified at pH 2.65 and 4.00 by isothermal titration calorimetry to be 4 and 2 protons per β-Lg molecule, respectively. By increasing the temperature to 65 °C, we discovered a secondary β-Lg concentration dependent coacervation step, where the formed particles change into large assemblies driven by entropy. These findings bring new insights to complex coacervation and its applicability in microencapsulation and drug delivery.

Molecular insights into alginate β-lactoglobulin A multivalencies-The foundation for their amorphous aggregates and coacervation

For improved control of biomaterial property design, a better understanding of complex coacervation involving anionic polysaccharides and proteins is needed. Here, we address the initial steps in condensate formation of β-lactoglobulin A (β-LgA) with nine defined alginate oligosaccharides (AOSs) and describe their multivalent interactions in structural detail. Binding of AOSs containing four, five, or six uronic acid residues (UARs), either all mannuronate (M), all guluronate (G), or alternating M and G embodying the block structural components of alginates, was characterized by isothermal titration calorimetry, nuclear magnetic resonance spectroscopy (NMR), and molecular docking. β-LgA was highly multivalent exhibiting binding stoichiometries decreasing from five to two AOSs with increasing degree of polymerization (DP) and similar affinities in the mid micromolar range. The different AOS binding sites on β-LgA were identified by NMR chemical shift perturbation analyses and showed diverse compositions of charged, polar and hydrophobic residues. Distinct sites for the shorter AOSs merged to accommodate longer AOSs. The AOSs bound dynamically to β-LgA, as concluded from saturation transfer difference and 1 H-ligand-targeted NMR analyses. Molecular docking using Glide within the Schrödinger suite 2016-1 revealed the orientation of AOSs to only vary slightly at the preferred β-LgA binding site resulting in similar XP glide scores. The multivalency coupled with highly dynamic AOS binding with lack of confined conformations in the β-LgA complexes may help explain the first steps toward disordered β-LgA alginate coacervate structures.

Unaided efficient transglutaminase cross-linking of whey proteins strongly impacts the formation and structure of protein alginate particles

•

Microbial transglutaminase (MTG) cross-linked >70% β-lactoglobulin (β-Lg) at pH 8.5.

•

Initial MTG catalyzed isopeptide bond formation caused partial unfolding of β-Lg.

•

>75% of whey protein cross-linked, forming hetero-polymers containing β-Lg.

•

50% less alginate is needed to form particles with cross-linked than with native β-Lg.

•

Cross-linked β-Lg and alginate formed suspendable hydrophobically driven particles.

There is a dogma within whey protein modification, which dictates the necessity of pretreatment to enzymatic cross-linking of β-lactoglobulin (β-Lg). Here microbial transglutaminase (MTG) cross-linked whey proteins and β-Lg effectively in 50 mM NaHCO₃, pH 8.5, without pretreatment. Cross-linked β-Lg spanned 18 to >240 kDa, where 6 of 9 glutamines reacted with 8 of 15 lysines. The initial isopeptide bond formation caused loss of β-Lg native structure with t_1/2 = 3 h, while the polymerization occurred with t_1/2 = 10 h. Further, cross-linking effects on protein carbohydrate interaction have been overlooked, leaving a gap in understanding of these complex food matrices. Complexation with alginate showed that β-Lg cross-linking decreased onset of particle formation, hydrodynamic diameter, stoichiometry (β-Lg/alginate) and dissociation constant. The complexation was favored at higher temperatures (40 °C), suggesting that hydrophobic interactions were important. Thus, β-Lg was cross-linked without pretreatment and the resulting polymers gave rise to altered complexation with alginate.

Physicochemical properties of kashk supplemented with encapsulated lemongrass extract

Kashk is a perishable fermented dairy product. Since chemical preservatives are harmful for human health, we aimed to study lemongrass (Cymbopogon citratus L.) as a natural preservative. First, we assessed the phytochemical properties of lemongrass extract. Then, we added lemongrass extract and microencapsulated lemongrass extract to kashk samples. Finally, we analyzed their physicochemical and sensorial properties during 60 days of storage. Catechin (419.04 ± 0.07 mg/L), gallic acid (319.67 ± 0.03 mg/L), and chloregenic acid (4.190 ± 0.002 mg/L) were found to be the predominant phenolic constituents in lemongrass. Total phenolics, total flavonoids, and antioxidant activity (IC50) values of the lemongrass extract were 26.73 mg GA/g, 8.06 mg Quercetin/g, and 2751.331 mg/L, respectively. The beads were spherical in shape with a 35.03-nm average particle diameter and 47.81% microencapsulation efficiency. The pH of the supplemented kashks decreased during the storage time. They showed lower acid degree values than the control at the end of storage. The peroxide, p-anisidine, and thiobarbituric acid values of the sample fortified with microencapsulated lemongrass extract were 6.15, 4.76, and 44.12%, respectively, being the lowest among the samples. This kashk sample had the highest hardness (570.62 ± 21.87 g), adhesiveness (18.10 ± 4.36 mJ), and cohesiveness (0.56 ± 0.25) but the lowest chewiness (72.66 ± 3.08 mJ) among the samples. It also had a better sensory profile than the control samples. Our results indicated that microencapsulated lemongrass extract could be incorporated into kashk to ensure suitable sensorial and textural properties. Furthermore, it may delay fat oxidation and lipolysis during storage.

Study on the mechanism of non-covalent interaction between rose anthocyanin extracts and whey protein isolate under different pH conditions

The non-covalent interaction between anthocyanin and dietary protein had an impact on their physicochemical property. The purpose of this study was to study the non-covalent interaction mechanism between rose anthocyanin extract (RAEs) and whey protein isolate (WPI), and further compare the interaction mechanism with pure anthocyanin (PC) and WPI. At pH 3.0 and pH 7.0, RAEs and WPI had non-covalent interactions in the two systems with two types of unequal and mutually influencing binding sites, and the interaction forces were both hydrogen bonds and van der Waals forces. Interestingly, PC and WPI also had non-covalent interactions in both systems, the number of which binding sites was about one type, and the forces were hydrogen bonds and van der Waals forces. In addition, a variety of spectral combination techniques indicated that RAEs and PC caused similar changes in the secondary structure of WPI.

The non-covalent interactions between whey protein and various food functional ingredients

In daily diet, Whey protein (WP) is often coexisted with various Food functional ingredients (FFI) such as proteins, polyphenols, polysaccharides and vitamins, which inevitably affect or interact with each other. Generally speaking, they may be interact by two different mechanisms: non-covalent and covalent interactions, of which the former is more common. We reviewed the non-covalent interactions between WP and various FFI, explained the effect of each WP-FFI interaction, and provided possible applications of WP-FFI complex in the food industry. The biological activity, physical and chemical stability of FFI, and the structure and functionalities of WP were enhanced through the non-covalent interactions. The development of non-covalent interactions between WP and FFI provides opportunities for the design of new ingredients and biopolymer complex, which can be applied in different fields. Future research will further focus on the influence of external or environmental factors in the food system and processing methods on interactions.

A solar-heated antibacterial sodium alginate aerogel for highly efficient cleanup of viscous oil spills

HYPOTHESIS

Major oil spills highlight the need for environmentally responsible and cost-effective recovery technologies. However, challenges remain for heavy oil spill recovery because of its high viscosity and low fluidity. To achieve this goal, an ecofriendly bio-based aerogel with efficient photothermal conversion ability was developed as a novel absorbent to achieve the fast removal of heavy oil spill by reducing the oil viscosity.

EXPERIMENTS

From the renewable and abundant raw material sodium alginate (SA), hydrophobic and antibacterial SA/graphene oxide/ZIF-8 aerogel (SAGZM) was successfully fabricated via freezing-drying and chemical vapor deposition (CVD) technique. A series of characterization and tests, including aerogel structure, selective wettability, photothermal conversion ability, crude oil removal capability, and antibacterial ability, have been investigated in detail. SAGZM aerogels have rich pore structure, high porosity, excellent mechanical properties, and better photothermal conversion efficiency.

FINDINGS

Under sunlight illumination, the recovery ability of SAGZM for heavy crude oil was investigated through infrared thermal imaging, oil permeability behavior analysis, and the continuous absorption for crude oil. In addition, these results are well supported by the theoretical liquid absorption coefficient. This study indicates that SAGZM is highly efficient in in situ regulating oil viscosity through its remarkably photothermal conversion capability. Importantly, SAGZM possesses an excellent antibacterial ability that is often neglected in the design of environmentally friendly materials in extending its service life. The findings of this work not only provide an eco-friendly bio-based aerogel material but also demonstrate that the photo-responsive SAGZM is efficient in heavy crude oil absorption. The proposed solar-heated SA-based aerogel provides a sustainable approach and material to solve the recovery problem of viscous crude oil spills.

Soy Protein Isolate/Sodium Alginate Microparticles under Different pH Conditions: Formation Mechanism and Physicochemical Properties

The effects of sodium alginate (SA) and pH value on the formation, structural properties, microscopic morphology, and physicochemical properties of soybean protein isolate (SPI)/SA microparticles were investigated. The results of ζ-potential and free sulfhydryl (SH) content showed electrostatic interactions between SPI and SA, which promoted the conversion of free SH into disulfide bonds within the protein. The surface hydrophobicity, fluorescence spectra, and Fourier transform infrared spectroscopy data suggested that the secondary structure and microenvironment of the internal hydrophobic groups of the protein in the SPI/SA microparticles were changed. Compared with SPI microparticles, the surface of SPI/SA microparticles was smoother, the degree of collapse was reduced, and the thermal stability was improved. In addition, under the condition of pH 9.0, the average particle size of SPI/SA microparticles was only 15.92 ± 0.66 μm, and the distribution was uniform. Rheological tests indicated that SA significantly increased the apparent viscosity of SPI/SA microparticles at pH 9.0. The maximum protein solubility (67.32%), foaming ability (91.53 ± 1.12%), and emulsion activity (200.29 ± 3.38 m²/g) of SPI/SA microparticles occurred at pH 9.0. The application of SPI/SA microparticles as ingredients in high-protein foods is expected to be of great significance in the food industry.

Maillard-Type Protein-Polysaccharide Conjugates and Electrostatic Protein-Polysaccharide Complexes as Delivery Vehicles for Food Bioactive Ingredients: Formation, Types, and Applications

Due to their combination of featured properties, protein and polysaccharide-based carriers show promising potential in food bioactive ingredient encapsulation, protection, and delivery. The formation of protein–polysaccharide complexes and conjugates involves non-covalent interactions and covalent interaction, respectively. The common types of protein–polysaccharide complex/conjugate-based bioactive ingredient delivery systems include emulsion (conventional emulsion, nanoemulsion, multiple emulsion, multilayered emulsion, and Pickering emulsion), microcapsule, hydrogel, and nanoparticle-based delivery systems. This review highlights the applications of protein–polysaccharide-based delivery vehicles in common bioactive ingredients including polyphenols, food proteins, bioactive peptides, carotenoids, vitamins, and minerals. The loaded food bioactive ingredients exhibited enhanced physicochemical stability, bioaccessibility, and sustained release in simulated gastrointestinal digestion. However, limited research has been conducted in determining the in vivo oral bioavailability of encapsulated bioactive compounds. An in vitro simulated gastrointestinal digestion model incorporating gut microbiota and a mucus layer is suggested for future studies.

Whole Wheat Crackers Fortified with Mixed Shrimp Oil and Tea Seed Oil Microcapsules Prepared from Mung Bean Protein Isolate and Sodium Alginate

Shrimp oil (SO) rich in n-3 fatty acids and astaxanthin, mixed with antioxidant-rich tea seed oil (TSO), was microencapsulated using mung bean protein isolate and sodium alginate and fortified into whole wheat crackers. SO and TSO mixed in equal proportions were emulsified in a solution containing mung bean protein isolate (MBPI) and sodium alginate (SA) at varied ratios. The emulsions were spray-dried to entrap SO-TSO in MBPI-SA microcapsules. MBPI-SA microcapsules loaded with SO-TSO showed low to moderately high encapsulation efficiencies (EE) of 32.26–72.09% and had a fair flowability index. Two selected microcapsules with high EE possessed the particle sizes of 1.592 and 1.796 µm with moderate PDI of 0.372 and 0.403, respectively. Zeta potential values were −54.81 mV and −53.41 mV. Scanning electron microscopic (SEM) images indicated that microcapsules were spherical in shape with some shrinkage on the surface and aggregation took place to some extent. Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) analyses of samples empirically validated the presence of SO-TSO in the microcapsules. Encapsulated SO-TSO showed superior oxidative stability and retention of polyunsaturated fatty acids (PUFAs) to unencapsulated counterparts during storage of 6 weeks. When SO-TSO microcapsules were fortified in whole wheat crackers at varying levels (0–10%), the crackers showed sensorial acceptability with no perceivable fishy odor. Thus, microencapsulation of SO-TSO using MBPI-SA as wall materials could be used as an alternative carrier system, in which microcapsules loaded with PUFAs could be fortified in a wide range of foods.

Formulation of infant formula with different casein fractions and their effects on physical properties and digestion characteristics

This study investigated whether casein (CN) fractions exhibit better physical properties and digestibility than native casein micelles presently used in the production of infant formula. The structural performance of native casein micelles (micellar casein concentrates, MCC), β-CN, κ-CN and β + κ-CN were explored, and physical properties and digestion characteristics (i.e., digestibility, particle size, zeta potential and microscopic morphology) of the infant formula with MCC, β-CN, κ-CN or β + κ-CN were determined to elucidate the applicability of these casein types in infant formula. Results indicated that the β + κ-CN infant formula solution had the largest particle size with the most unstable potential. Moreover, both β-CN and κ-CN infant formula showed high solubility, while κ-CN displayed the lowest foaming capacity and high foaming stability. β-CN infant formula expressed an effective digestibility property, however, it possessed the largest particle size after gastrointestinal digestion. Therefore, β-CN fraction infant formula showed better digestibility than casein infant formula, and thus this work provides a theoretical basis for the development of infant formula.

Effects of Radiation sterilization Dose on the Molecular Weight and Gelling Properties of Commercial Alginate Samples

To estimate the molecular weight (Mw) and gelling properties, a total of 26 alginate samples consisting of control (n = 13) and 15 kGy γ-irradiated (n = 13) samples were characterized through viscometric and gel permeation chromatography (GPC-MALLS) methods. Based on the observations, a remarkable decrease in the intrinsic viscosity of all samples of alginates was evident due to the effects of radiation, with a linear relationship between viscosity and concentration in 0.01 M NaCl solution. The correlation among the Mw, percentage mass recovery, radii of gyration (Rz/Rg), and percentage reduction of Mw assessed by GPC was significant. The Mw decreased dramatically (from 3.1 × 105 to 0.49 × 105 mole/g in sample no. 12) by the effect of radiation with momentous relation to the % reduction of the molecular weight. The highest molecular weight reduction (84%), which is the most sensitive to γ-radiation, and the average reduction rate was ≥50%. The mass recovery was 100% obtained from samples no. 1,3,4,5,7,12, and 13, while the rest of the samples’ recovery rate was significantly higher. The reduction rate of mass molecular weight (Mw) is higher than the average molecular weight (Mv), but they showed a sensitivity towards radiation, consequently their performance are different from each other. The stability test was performed as a critical behaviour in the control, recurrently same as in the irradiated samples. Thus, the sterilization dose of 15 kGy for the Mw distribution, and subsequently for the characterization, was significantly effective.

Study of biological activities and physicochemical properties of Yamú (Brycon siebenthalae) viscera hydrolysates in sodium alginate-based edible coating solutions

The fishing industry produces waste such as viscera, which is an environmental problem for many countries. Obtaining protein from these wastes are useful for the food industry. In this study, the chemical composition, amino acid profile, solubility, digestibility and thermal properties of Yamú protein isolate (PI) and its hydrolysates obtained by enzymatic hydrolysis were characterized. The hydrolysates (0.05, 0.1, 0.5, 1 and 2% w/v) were mixed with a sodium alginate-based solution to form an edible coating solution (ECS). Antioxidant capacity antimicrobial activity, Zeta potential (ζ) and adsorption kinetics properties were determined. PI contains 88% (w/w) protein showing better solubility, digestibility and thermal stability properties. The hydrolysate concentrations with DPPH inhibitory ECS were 0.1 and 0.5% (w/v). The kinetic properties of ECS showed good stability and excellent adsorption. These results suggest that this Yamú protein has high nutritional potential as an ingredient for the production of functional foods.

Organic Fouling Impact in a Direct Contact Membrane Distillation System Treating Wastewater: Experimental Observations and Modeling Approach

This study aims to investigate the effect of operational conditions on organic fouling occurring in a direct contact membrane distillation (DCMD) system used to treat wastewater. A mixed solution of sodium alginate (SA) and bovine serum albumin (BSA) was used as a feed solution to simulate polysaccharides and proteins, respectively, assumed as the main organic foulants. The permeate flux was observed at two feed temperatures 35 and 50 °C, as well as three feed solution pH 4, 6, and 8. Higher permeate flux was observed for higher feed temperature, which allows higher vapor pressure. At higher pH, a smaller particle size was detected with lower permeate flux. A mathematical model based on mass balance was developed to simulate permeate flux with time by assuming (i) the cake formation controlled by attachment and detachment of foulant materials and (ii) the increase in specific cake resistance, the function of the cake porosity, as the main mechanisms controlling membrane fouling to investigate the fouling mechanism responsible of permeate flux decline. The model fitted well with the experimental data with R² superior to 0.9. High specific cake resistance fostered by small particle size would be responsible for the low permeate flux observed at pH 8.

Effect of heat treatment on the structure and stability of Grass pea (Lathyrus sativus) protein isolate/Alyssum homolocarpum seed gum nanoparticles

In the present study, Grass pea protein isolate (GPPI)- Alyssum homolocarpum seed gum (AHSG) complex nanoparticles were formed through two fabrication methods and their physicochemical properties, structure and stability against sodium chloride and different pHs were investigated. Type 1 particles were formed by creating GPPI nanoparticles, and then coating them with AHSG; while Type 2 particles were fabricated through the heat treatment of GPPI-AHSG complexes at 85 °C for 15 min. The preparation methods did not influence the magnitude of electrical charges on biopolymer particles. The particle size analysis revealed that Type 2 particles had lower mean diameter (d = 360.20 nm) compared to Type 1 particles (d = 463.22 nm). Structural properties of Type 1 and Type 2 particles were determined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), Differential scanning calorimetry (DSC), Atomic force microscopy (AFM), and transmission electron microscopy (TEM). Hydrogen bonding, electrostatic and hydrophobic interactions were the main driving forces contributed to the formation of both GPPI-AHSG complex particles. Assessments of morphological and structural properties also indicated that both Type 1 and 2 particles had spherical shapes and heat treatment increased the ordered intermolecular structures in biopolymer particles. Type 2 particles had higher denaturation temperature and better pH and salt stability when compared to Type 1 particles. These results indicate that thermal treatment was effective for the fabrication of stable GPPI-AHSG complex nanoparticles.

Short communication: The effect of pectin and sodium alginate on labans made from camel milk and bovine milk

Camel milk (CM) is gaining scientific attention due to its potential health and therapeutic benefits. Fermented drinkable yogurts (labans) were prepared from CM and bovine milk (BM) using mixed Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus bacteria supplemented with 1 of 2 hydrocolloids: pectin (0.1-0.3%) or sodium alginate (0.1-0.5%). The different labans were compared by studying their acidity and rheology as well as their structural and sensory properties. The CM and BM labans had titratable acidity values that ranged from 0.85 to 1.27 and 0.61 to 0.93%, respectively. Pectin at 0.2% enhanced the rheological properties of BM labans, but had no effect in CM labans. Sodium alginate at 0.3% and 0.5% increased viscosity, elastic or storage modulus (G'), and viscous or loss modulus (G″) values for both types of laban. Scanning electron microscopy indicated that the CM laban contained lower levels of "spike-like structures" than BM laban, and that the addition of hydrocolloids improved this effect. Quantitative descriptive sensory analysis showed that CM labans fortified with either 0.2% pectin or 0.3% sodium alginate were comparable to commercial BM laban in viscous mouthfeel. Fortified CM labans were more acidic and had stronger flavors than unfortified samples. Overall, this study demonstrated that the addition of sodium alginate or pectin at intermediate levels permits production of palatable CM labans of a satisfactory viscous consistency.

Construction of a Superhydrophobic Sodium Alginate Aerogel for Efficient Oil Absorption and Emulsion Separation

Bio-based aerogels serve as potential materials in separation of oil/water mixtures. Nevertheless, there remain some key challenges, including expensive/toxic organic cross-linkers, unpromising reusability, and poor performance in emulsion separation. Hereby, a novel, robust, and superhydrophobic sodium alginate/graphene oxide/silicon oxide aerogel (SA/GO/SiO₂-M) was fabricated by simple calcium ion cross-linking self-assembly, freeze-drying, and chemical vapor deposition methods based on the renewable and abundant raw materials. The as-prepared SA-based aerogel possesses high absorbency for varieties of organic solvents and oils. Importantly, it shows high efficiency in the separation of surfactant-stabilized water-in-oil emulsions. SA/GO/SiO₂-M aerogels display excellent reusability in both absorption and separation because of their good mechanical properties in the air and oil phase, and the mechanism in emulsion separation is discussed. This study shows that SA/GO/SiO₂-M aerogels are a promising material in treating oil contaminants from different fields.

Impact of Alginate Mannuronic-Guluronic Acid Contents and pH on Protein Binding Capacity and Complex Size

Alginates, serving as hydrocolloids in the food and pharma industries, form particles at pH < 4.5 with positively charged proteins, such as β-lactoglobulin (β-Lg). Alginates are linear anionic polysaccharides composed of 1,4-linked β-d-mannuronate (M) and α-l-guluronate (G) residues. The impact of M and G contents and pH is investigated to correlate with the formation and size of β-Lg alginate complexes under relevant ionic strength. It is concluded, using three alginates of M/G ratios 0.6, 1.1, and 1.8 and similar molecular mass, that β-Lg binding capacity is higher at pH 4.0 than at pH 2.65 and for high M content. By contrast, the largest particles are obtained at pH 2.65 and with high G content. At pH 4.0 and 2.65, the stoichiometry was 28-48 and 3-10 β-Lg molecules bound per alginate, respectively, increasing with higher M content. The findings will contribute to the design of formation of the desired alginate-protein particles in the acidic pH range.

Preparation of aminated fish scale collagen and oxidized sodium alginate hybrid hydrogel for enhanced full-thickness wound healing

Acute full-thickness wounds require a more extended healing period, thus increasing the risk of infection. Severe infection frequently resulted in wound ulceration, necrosis, and even life-threatening complications. Here, a hybrid hydrogel comprising aminated collagen (AC), oxidized sodium alginate (OSA), and antimicrobial peptides (polymyxin B sulfate and bacitracin) was developed to enhance full-thickness wound healing. The AC with low immunogenicity and high biocompatibility was made from marine fish scales, which are eco-friendly, low-cost, and sustainable. The cross-linked hydrogel was formed by a Schiff base reaction without any catalysts and additional procedures. As expected, the presented hybrid hydrogel can effectively against E. coli and S. aureus, as well as promote cell growth and angiogenesis in vitro. In addition, the hydrogel can promote full-thickness wound healing in a rat model through accelerating reepithelialization, collagen deposition, and angiogenesis. Our work demonstrated that the hybrid hydrogel has promising applications in the field of wound healing, which would prompt the utilization of marine fish resources during food processing.

Protein Encapsulation Using Complex Coacervates: What Nature Has to Teach Us

Protein encapsulation is a growing area of interest, particularly in the fields of food science and medicine. The sequestration of protein cargoes is achieved using a variety of methods, each with benefits and drawbacks. One of the most significant challenges associated with protein encapsulation is achieving high loading while maintaining protein viability. This difficulty is exacerbated because many encapsulant systems require the use of organic solvents. By contrast, nature has optimized strategies to compartmentalize and protect proteins inside the cell-a purely aqueous environment. Although the mechanisms whereby aspects of the cytosol is able to stabilize proteins are unknown, the crowded nature of many newly discovered, liquid phase separated "membraneless organelles" that achieve protein compartmentalization suggests that the material environment surrounding the protein may be critical in determining stability. Here, encapsulation strategies based on liquid-liquid phase separation, and complex coacervation in particular, which has many of the key features of the cytoplasm as a material, are reviewed. The literature on protein encapsulation via coacervation is also reviewed and the parameters relevant to creating protein-containing coacervate formulations are discussed. Additionally, potential opportunities associated with the creation of tailored materials to better facilitate protein encapsulation and stabilization are highlighted.

Aqueous self-assembly of arginine and K8SiW11O39: fine-tuning the formation of a coacervate intended for sprayable anticorrosive coatings

Coacervates are commonly thought to be formed from the liquid-liquid phase separation of macromolecules, such as oppositely charged polyelectrolytes, proteins or peptides. Unlike conventional systems, we here show an entirely novel coacervate obtained from the self-assembly of arginine (Arg) and K₈[α-SiW₁₁O₃₉] (SiW₁₁) in water. The formation of the coacervate Arg/SiW₁₁ is confirmed by combined techniques, including turbidity, rheology, optical microscopy, and scanning and transmission electron microscopy. Assessment of the rheological response reveals that the complex coacervate exhibits shear thinning behaviour. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, elemental analysis and thermogravimetric analysis are used to characterize the coacervate. The thermodynamic parameters of the coacervation are monitored by isothermal titration calorimetry (ITC), which identifies that the formation of the coacervate by mixing of Arg and SiW₁₁ is driven by a combination of entropic and enthalpic effects. The resultant coacervate shows a typical upper critical solution temperature (UCST) phenomenon, which is strongly dependent on the concentration of the species. Furthermore, we demonstrate that the coacervation could be tuned by stoichiometry and pH. A phase diagram for the complexation of Arg and SiW₁₁ thus has been constructed using turbidity measurements. Such a phase diagram is a very useful tool for the preparation of coacervates from a specific combination of Arg and SiW₁₁. Finally, the acid induced gelation of the coacervate has been explored to fabricate an anticorrosive coating to protect a copper plate from exposure to acid vapour.

Effects of Molecular Weight and Guluronic Acid/Mannuronic Acid Ratio on the Rheological Behavior and Stabilizing Property of Sodium Alginate

The aim of this study was to prepare sodium alginates (SAs) with different molecular weight and G/M ratio, and characterize their rheological behaviors and emulsifying properties. The result of Fourier transform infrared (FTIR) showed that the chemical bonds among the β-d-mannuronic acid- (M-), α-l-guluronic acid- (G-), and MG-sequential blocks in the SA chains were not changed significantly by acid treatment. Meanwhile, the molecular weight and G/M ratio of the SA exhibited drastic variation after acid modification. The result of rheological analysis suggesting that the apparent viscosity of SA reduced from 30 to 16.4 mPa.s with the increase of shear rate, reveals that SA solution belongs to pseudoplastic liquid. Also, the apparent viscosity of acid-modified SA solution dropped rapidly with the decrease of the molecular weight. The properties of emulsions stabilized by SA, SA-Ms, and commercial SAs were evaluated via the interface tensiometry and determination of the zeta potential, droplet size, creaming index (CI), and Turbiscan stability index (TSI). Compared with the SA-stabilized emulsion, the interfacial tension of the emulsion stabilized by SA-M increased with the decrease of the molecular weight reduced at the similar M/G ratio. The decrease in zeta potential and the increase in TSI of the emulsion were observed with the decrease of molecular weight, indicating that molecular weight plays an important role on the emulsifying ability of SA. In addition, the SA with low G/M ratio can form emulsions with stable and fine droplets.

Quantitative analysis of binding affinities and characterization of β-lactoglobulin and λ-carrageenan as a function of pH

λ-Carrageenan (λcar) interacted with β-lactoglobulin (βlg) immediately to form βlg-λcar complexes when used as an additive in milk. The formation of complexes is the key process through which to explore the bioapplication of λcar, which is a complicated process and influenced by many factors. In this study, the formation process and effect of pH were ascertained by the binding affinity, hydrodynamic diameter, and secondary structure. Results showed that the interaction was spontaneously exothermic and the complexes were soluble. The binding affinities (Ka) decreased from 9.0 ± 1.3 × 10⁵ to 1.3 ± 0.8 × 10⁵  M^-1 , and the stoichiometry also decreased as the pH was increased from 4 to 7. Furthermore, DLS showed a larger hydrodynamic diameter of the complexes at lower pH. Moreover, the complexes induced a change in the secondary structural components of βlg at lower pH. PRACTICAL APPLICATIONS: The secondary structure of βlg was changed by the interaction of λcar, which resulted in βlg-λcar complexes under acidic conditions. The soluble βlg-λcar complexes showed a good stability against aggregation. Thus, they can enhance the textural properties and stability of acidic dairy drinks, and can be used to accurately formulate ingredients in the food ingredient industry.

Formation of Nanocomplexes between Carboxymethyl Inulin and Bovine Serum Albumin via pH-Induced Electrostatic Interaction

As a functional polysaccharide, inulin was carboxymethylated and it formed nanocomplexes with bovine serum albumin (BSA). The success of obtaining carboxymethyl inulin (CMI) was confirmed by a combination of Fourier transform Infrared (FT-IR), Raman spectroscopy, gel permeation chromatography (GPC), and titration. The effects of pH and ionic strength on the formation of CMI/BSA nanocomplexes were investigated. Our results showed that the formation of complex coacervate (pHφ1) and dissolution of CMI/BSA insoluble complexes (pHφ2) appeared in pH near 4.85 and 2.00 respectively. FT-IR and Raman data confirmed the existence of electrostatic interaction and hydrogen bonding between CMI and BSA. The isothermal titration calorimetry (ITC) results suggested that the process of complex formation was spontaneous and exothermic. The complexation was dominated by enthalpy changes (∆Η < 0, ∆S < 0) at pH 4.00, while it was contributed by enthalpic and entropic changes (∆Η < 0, ∆S > 0) at pH 2.60. Irregularly shaped insoluble complexes and globular soluble nanocomplexes (about 150 nm) were observed in CMI/BSA complexes at pH 4.00 and 2.60 while using optical microscopy and atomic force microscopy, respectively. The sodium chloride suppression effect on CMI/BSA complexes was confirmed by the decrease of incipient pH for soluble complex formation (or pHc) and pHφ1 under different sodium chloride concentrations. This research presents a new functional system with the potential for delivering bioactive food ingredients.