Function Of NaCl Concentration Research Articles

L version of the transformed Kedem-Katchalsky equations for membrane transport of electrolyte solutions and internal energy conversion.

One of the important formalisms of non-equilibrium thermodynamics is Peusner network thermodynamics. The description of the energy conversion in membrane processes, i.e., the conversion of the internal energy of the system into the dissipated energy and the free energy used for the work associated with the transport of solution components, allows us to describe the relationship between these energies and the thermodynamic forces acting in the membrane system. The aim of this study was to develop a procedure to transform the Kedem-Katchalsky equations for the transport of binary electrolytic solutions across a membrane into the Kedem-Katchalsky-Peusner equations based on Peusner network thermodynamics. The conversion of electrochemical energy to free energy in the membrane system was also determined. The nanobiocellulose biomembranes (Biofill) were the subject of the study with experimentally determined transport parameters for aqueous NaCl solutions. The research method is the Kedem-Katchalsky-Peusner formalism for binary electrolyte solutions with introduced Peusner coefficients. The coefficients of the L version of the membrane transport equations and the Peusner coupling coefficients were derived as functions of NaCl concentration in the membrane. Based on these coefficients, the fluxes of internal energy of the system, energy dissipated to the surroundings and free energy related to the transport of electrolyte across the membrane were calculated and presented as functions of the osmotic and electric forces on the membrane. The Peusner coefficients obtained from the transformations of the coefficients of the Kedem-Katchalsky formalism for the transport of electrolyte solutions through the Biofill membrane were used to calculate the coupling coefficients of the membrane processes and the dissipative energy flux. The dissipative energy flux takes the form of a quadratic form due to the thermodynamic forces on the membrane - second degree curves are obtained. Moreover, the dissipative energy flux as a function of thermodynamic forces allowed us to examine the energy conversion in transport processes in the membrane system.

Comparing polymer-surfactant complexes to polyelectrolytes

HypothesisUnderstanding the complex interactions between polymers and surfactants is required to optimise commercially relevant systems such as paint, toothpaste and detergent. Neutral polymers complex with surfactants, forming ‘pearl necklace’ structures that are often conceptualised as pseudo-polyelectrolytes. Here we pose two questions to test the limits of this analogy: Firstly, in the presence of salt, do these polymer-surfactant systems behave like polyelectrolytes? Secondly, do polymer-surfactant complexes resist geometric confinement like polyelectrolytes? ExperimentsWe test the limits of the pseudo-polyelectrolyte analogy through studying a poly(N-isopropylacrylamide) (PNIPAM) brush in the presence of sodium dodecylsulfate (SDS). Brushes are ideal for interrogating pseudo-polyelectrolytes, as neutral and polyelectrolyte brushes exhibit distinct and well understood behaviours. Spectroscopic ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and neutron reflectometry (NR) were used to monitor the behaviour and structure of the PNIPAM-SDS system as a function of NaCl concentration. The ability of the PNIPAM-SDS complex to resist geometric confinement was probed with NR. FindingsAt a fixed SDS concentration below the zero-salt CMC, increasing NaCl concentration <100 mM promoted brush swelling due to an increase in osmotic pressure, not dissimilar to a weak polyelectrolyte. At these salt concentrations, the swelling of the brush could be described by a single parameter: the effective CMC. However, at high NaCl concentrations (e.g., 500 mM) no brush collapse was observed at all (non-zero) concentrations of SDS studied, contrary to what is seen for many polyelectrolytes. Study of the polymer-surfactant system under confinement revealed that the physical volume of surfactant dominates the structure of the strongly confined system, which further differentiates it from the polyelectrolyte case.

Dynamic and Static Properties of Aqueous NaCl Solutions at 25°C as a Function of NaCl Concentration: A Molecular Dynamics Simulation Study

We present the result of molecular dynamics (MD) simulations to calculate the molar conductivity Λ m = λ N a + + λ C l − of NaCl in SPC/E water at 25°C as a function of NaCl concentration (c) using Ewald sums employing a velocity Verlet algorithm. It is found that the MD result for Λm with Ewald sum parameter κ = 0.10 Å−1 gives the closest one to the experimental data and that the obtained radial distribution functions g i i (r) with κ = 0.10 Å−1 show a dramatic change with a very deep minimum of g NaCl (r) and, as a result, sharp maxima of g NaNa (r) and g ClCl (r) at the distance 9.95 Å, which indicates a characteristic of ionic atmosphere, the basis of the Debye–Hückel theory of ionic solutions. The static and dynamic properties of NaCl (aq) solutions are analyzed in terms of radial distribution functions, hydration numbers, coordination numbers around Na+ and Cl−, residence times of water around Na+ and Cl−, water diffusion, and ion-ion electrostatic energies to explain the behavior of the molar conductivity Λm of NaCl obtained from our MD simulations.

Silver Solubility in Supercritical Fluids in a Wide Range of NaCl Concentration (0.6–50 wt %)—Experimental and Thermodynamic Description

The solubility of Agcr has been measured in a 0.1m (mol·(kg H2O)−1) solution of HCl at a fixed hydrogen content (∼0.5m) as a function of NaCl concentration from 0.1 to 18m at temperatures ranging f...

Salt accumulation and effects within foliage of Tilia × vulgaris trees from the street greenery of Riga, Latvia

Green infrastructures within sprawling cities provide essential ecosystem services, increasingly undermined by environmental stress. The main objective in this study was to relate the allocation patterns of NaCl contaminants to injury within foliage of lime trees mechanistically and distinguish between the effects of salt and other environmental stressors. Using field material representative of salt contamination levels in the street greenery of Riga, Latvia, the contribution of salt contaminants to structural and ultrastructural injury was analyzed, combining different microscopy techniques. On severely salt-polluted and dystrophic soils, the foliage of street lime trees showed foliar concentrations of Na/Cl up to 13,600/16,750 mg kg−1 but a still balanced nutrient content. The salt contaminants were allocated to all leaf blade tissues and accumulated in priority within mesophyll vacuoles, changing the vacuolar ionic composition at the expense of especially K and Ca. The size of mesophyll cells and vacuoles was increased as a function of NaCl concentration, suggesting impeded transpiration stream. In parallel, the cytoplasm showed degenerative changes, suggesting indirect stress effects. Hence, the lime trees in Riga showed tolerance to the dystrophic environmental conditions enhanced by salt pollution but their leaf physiology appeared directly impacted by the accumulation of contaminants within foliage.

Fungal spore adhesion on glycidoxypropyltrimethoxy silane modified silica nanoparticle surfaces as revealed by single cell force spectroscopy.

Thin film coatings prepared from commercially available glycidoxypropyltrimethoxysilane (GPS) modified silica nanoparticles (SiNPs) (Bindzil® CC301 and Bindzil® CC302) have previously shown excellent antifouling performance against a broad range of microbes [Molino et al., "Hydration layer structure of biofouling-resistant nanoparticles," ACS Nano 12, 11610 (2018)]. In this work, single cell force spectroscopy (SCFS) was used to measure the biological interactions between Epicoccum nigrum fungal spores and the same silica nanoparticle-based surfaces used in the aforementioned study, including a: glass coverslip, unmodified SiNP coatings, and both low (Bindzil® CC301) and high density (CC302) GPS functionalized SiNP coatings as a function of NaCl concentration. From the SCFS curves, the spore adhesion to the surface was greatest on the glass coverslip (20-80 nN) followed by the unmodified SiNP (3-5 nN) across all salt concentrations. Upon approach to both surfaces, the spores showed a long-range attraction generally with a profile characteristic of biointeractions and likely those of the outer cell wall structures or biological constituents. The attractive force allowed the spores to initially adhere to the surface and was found to be linearly proportional to the spore adhesion. In comparison, both high and low density GPS-SINP significantly reduced the spore adhesion (0.5-0.9 nN). In addition, the spore adhesion on high density GPS-SiNP occurred in only 14%-27% of SCFS curves (40%-48% for low density GPS-SiNP) compared to 83%-97% for the unmodified SiNP, indicating that in most cases the GPS functionalization completely prevented spore adhesion. The GPS-SiNP surfaces conversely showed a long-range electrostatic repulsion at low 1mM NaCl that was replaced by short-range repulsion at the higher salt concentrations. From the findings, it is proposed that the attractive force is a critical step in initial adhesion processes of the spore. The effective antifouling properties of the GPS are attributed to the ability to negate the attractive forces, either through electrostatic repulsion in low salt conditions and primarily from short-range repulsion correlating to the previously reported combined steric-hydration effect of the GPS functionalization on SiNP coatings.

Tunable Dewatering Behavior of Montmorillonite Suspension by Adjusting Solution pH and Electrolyte Concentration

Montmorillonite is always a troublemaker for the dewatering in coal processing since its existence can decrease the rates of sedimentation and filtration of coal slurry. To eliminate the adverse effect of montmorillonite, adjusting the slurry pH and adding electrolytes are always the key methods. However, the underlying mechanism still needs to be further studied. The dewatering of Na-montmorillonite (Na-Mt) suspensions has been studied as a function of NaCl concentration (10−3, 10−2, and 10−1 M) at different pH values (6.0, 7.7, 8.1, 9.2). The point of zero charge of edge surface of Na-Mt (pHPZC,edge) appeared at the pH value of 6.8. The sedimentation and rheology experiments described the coagulation and flow behaviors of Na-Mt suspensions, respectively. The Na-Mt suspension coagulated spontaneously at low salt concentration with the pH ~ 6.0. For the pH &gt; pHPZC,edge, the height of the sediment bed reduced and apparent viscosity increased with the increase of the electrolyte concentration. The filtration properties were evaluated on the basis of Darcy’s law. The obtained result clearly demonstrated that the filtration rate was accelerated with the increase of pH and electrolyte concentration. The modes of particle association and its effect on filtration performance were discussed. Moreover, a comparison with related results from the literature was performed. At pH ~ 6 and low electrolyte concentration, the positively charged Edge surfaces and negatively charged Face surfaces coagulate rapidly to form a sealed structure by electrostatic attraction. Furthermore, inside this sealed structure, the water molecules cannot be removed in the filtration process easily. However, by increasing the electrolyte concentration at pH &gt; pHPZC,edge, the gradually formed Face/Face structure increases the filtration rate sharply because of the inhibiting effect of the electric double layer (EDL) and the osmotic expansion. Therefore, adjusting solution conditions of the aqueous suspension to tune the particle coagulation behavior is one of the effective methods to solve the problem of montmorillonite dewatering.

Improvement in the water resistance of MAPC coatings as a function of NaCl concentration

This study focused on the waterproofing effectiveness of magnesium ammonium phosphate cement (MAPC) coatings at different sodium chloride (NaCl) concentrations (0, 3, 5 and 7%). It included qualitative analyses and quantitative tests of the effect of sodium chloride on three characteristics: tensile strength, water absorption rate and thickness of coatings. The influence of the changes in the structure and composition of MAPC coatings on their water resistance performance was also analyzed. It was found that 3% sodium chloride concentration could remarkably improve the waterproofing effect of MAPC coatings. Another finding showed that tensile strength, water absorption rate and coating thickness increased at the very beginning but these decreased as the sodium chloride content increased. Moreover, compared with other concentrations, the structure and composition of MAPC coatings containing 3% sodium chloride were found to be stable in water. The coatings were bonded to the concrete more tightly, which resulted in a more compact structure and thus a higher water resistance effect.

Salt effects on the structural tailoring of layer-by-layer assembled polyelectrolyte complexes and salt-containing polyelectrolyte films

Structural tailoring of layer-by-layer (LbL) assembled polymeric films prepared by alternate deposition of polyelectrolyte-polyelectrolyte complexes (PECs) and oppositely charged salt-containing polyelectrolyte was systematically studied as a function of NaCl concentration in the polyelectrolyte solution. At pH 9.3, positively charged poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) complexes (denoted as PAH-PAA9.3) could be LbL assembled with poly(sodium 4-styrenesulfonate) (PSS) to produce PSS/PAH-PAA9.3 films even with high NaCl concentration in PSS solution. Moreover, both the thickness and structure of the films were strongly depended on the concentration of NaCl in PSS solution. The salt in PSS solution can influence the conformation of PSS chains, but cannot interfere with the interaction and structure of PAH-PAA complexes deposited on substrates. Therefore, at relatively high NaCl concentration, a rough surface with hierarchical micro- and nanostructures can be obtained due to the coiled conformation and increased rigidness of PSS when they were LbL deposited with PAH-PAA complexes. By contrast, LbL deposition of flexible and extended PSS with PAH-PAA complexes at low NaCl concentration can produce a thin film with smooth structure. The present study is meaningful in deeply understanding the salt effect on the deposition behavior and structural tailoring of LbL assembled PECs and salt-containing polyelectrolyte films.

Effets de la salinité et du stress hydrique sur la germination des graines de Hedysarum flexuosum (Fabaceae)

Effects of salt and water stress on seed germination of Hedysarum flexuosum (Fabaceae ).— Hedysarum flexuosum L ., commonly called Sulla has been the subject of numerous studies which have demonstrated its forage and pastoral potential . Previous researches on the biochemical composition of this species have revealed a high nutritional value and positioned it as an alternative to the imported food for goat and sheep raising . The authors mention the richness of Sulla in proteins (22.5 % g / Kg of dry matter ), lipids and minerals . They also note a digestibility rate very similar to those of other forage legumes grown such as alfalfa . The species H . flexuosum or Sulla is reported in Algeria and Morocco on marl and marl-limestone substrates in regions with average rainfall greater than 550 mm . This study consists of an ecophysiological evaluation of the seed germination phase of H . flexuosum through the effects of salt and water stress on the germination rate (GT ) of this species . H . flexuosum pods were collected at maturity at a station in Ouadhia commune in northern Algeria . The seeds extracted from the pods were treated with 5 % sodium hypochlorite for 5 minutes and then rinsed three times with distilled water . In order to avoid any integumentary dormancy , a slight scarification of the seed surfaces was carried out . They were then watered with increasing concentration NaCl solutions (2 , 4 , 6 , 8 , and 10 g / l ), for the salinity test and by solutions of polyethylene glycol 6000 (PEG -6000 ) corresponding to pressures of : -1 bar, -3 bars, -7 bars , -9.25 bars respectively for the water stress . A batch of control seeds was watered with distilled water . The results of the germination rate (GT ) and mean germination time (MGT ) were analysed by an ANOVA using the stat box software (one parameter analysis : NaCl concentration for salt stress and PEG concentration for water stress ). The ANOVA analysis was completed by the Newman and Keuls test when it reveals a significant variation . Results show that GT variation as a function of NaCl concentrations is highly significant (P &lt; 0.001 ). Seed GT decreases in response to increased NaCl concentration in the imbibitions substrate . The higher osmotic pressure is , the greater the rate of reduction of the germinative capacity increases . The influence of salinity is in fact significantly perceptible from 2 g / l with a GT of 74 % corresponding to a reduction rate of 18.7 %. The concentration inducing the reduction of the germination of 50 % (LD 50 ) is between 4 and 6 g / l of NaCl . The germination is practically inhibited at the highest concentration tested (10 g / l ). Analysis of the variance of the MGT factor of H . flexuosum shows that it increases significantly with elevated environmental salinity . In the controls , MGT is 2.37 days but extends to 8 days at the dose of 10 g / l of NaCl . The effect of salinity on germination kinetics is manifested by the germination retardation caused by the increasing concentrations of NaCl and PEG substrate (first phase of germination ). It could be explained by the prolongation of the latency phase corresponding to the time required for the imbibition of the seeds to trigger the germination process . Our results show that the highest GT is obtained in the control seeds (94 %). At the osmotic pressure of -1 bar , the germinative capacity is reduced by 60.63 % compared to the control . GT decreases with increasing osmotic pressure of the seed imbibitions substrate . At the pressure of -3 bars the germination drop reached 90.42 %. The germination is completely inhibited at the pressure of -9.25 bars . Like GT , the MGT required for H . flexuosum seeds increases with osmotic pressure . This is tripled at -7 bars pressure compared to the controls . H . flexuosum appears to be more sensitive to salinity compared to several Tunisian cultivars of H . coronarium (LD 50 to -2.11 bars for water stress ).

Electrolytes Related Dynamic Mechanical Properties of Nanoconfined Water

Charged surfaces and electrolytes play an important role in many scientific and technological applications such as molecular friction, transport through bio-membranes, and generation of electrochemical energy. Using a home-built ultra-sensitive atomic force microscope, we have measured the stiffness, damping coefficient, and Maxwell’s relaxation time of a few molecular layers thin film of electrolytic water against atomically smooth mica surface. Water containing NaCl and CsCl have been compared with ultrapure water. The viscoelastic properties of the nanoconfined film exhibit a strong dependence on the compression rate of the film as well as the type of electrolyte present. The increase in Maxwell’s relaxation time as a function of NaCl concentration gives rise to a solidlike dynamic mechanical response under quasi-static conditions (compression rate = 0.2 nm/s). In contrast, the CsCl containing electrolytic water seems to suppress the solidlike dynamic mechanical behavior, which results from an apparent jamming of the molecules during a squeeze-out, as suggested elsewhere (Khan et al., Phys. Rev. Lett. 2010). These results suggest that the size and hydration number of ions play an important role in nanoconfined water.

Electrolytes Related Dynamic Mechanical Properties of Nanoconfined Water

Charged surfaces and electrolytes play an important role in many scientific and technological applications such as molecular friction, transport through bio-membranes, and generation of electrochemical energy. Using a home-built ultra-sensitive atomic force microscope, we have measured the stiffness, damping coefficient, and Maxwell’s relaxation time of a few molecular layers thin film of electrolytic water against atomically smooth mica surface. Water containing NaCl and CsCl have been compared with ultrapure water. The viscoelastic properties of the nanoconfined film exhibit a strong dependence on the compression rate of the film as well as the type of electrolyte present. The increase in Maxwell’s relaxation time as a function of NaCl concentration gives rise to a solidlike dynamic mechanical response under quasi-static conditions (compression rate = 0.2 nm/s). In contrast, the CsCl containing electrolytic water seems to suppress the solidlike dynamic mechanical behavior, which results from an apparent jamming of the molecules during a squeeze-out, as suggested elsewhere (Khan et al., Phys. Rev. Lett. 2010). These results suggest that the size and hydration number of ions play an important role in nanoconfined water.

The Charge Properties of Phospholipid Nanodiscs

Phospholipids (PLs) are a major, diverse constituent of cell membranes. PL diversity arises from the nature of the fatty acid chains, as well as the headgroup structure. The headgroup charge is thought to contribute to both the strength and specificity of protein-membrane interactions. Because it has been difficult to measure membrane charge, ascertaining the role charge plays in these interactions has been challenging. Presented here are charge measurements on lipid Nanodiscs at 20°C in 100 mM NaCl, 50 mM Tris, at pH 7.4. Values are also reported for measurements made in the presence of Ca2+ and Mg2+ as a function of NaCl concentration, pH, and temperature, and in solvents containing other types of cations and anions. Measurements were made for neutral (phosphatidylcholine and phosphatidylethanolamine) and anionic (phosphatidylserine, phosphatidic acid, cardiolipin, and phosphatidylinositol 4,5-bisphosphate (PIP2)) PLs containing palmitoyl-oleoyl and dimyristoyl fatty acid chains. In addition, charge measurements were made on Nanodiscs containing an Escherichia coli lipid extract. The data collected reveal that 1) POPE is anionic and not neutral at pH 7.4; 2) high-anionic-content Nanodiscs exhibit polyelectrolyte behavior; 3) 3 mM Ca2+ neutralizes a constant fraction of the charge, but not a constant amount of charge, for POPS and POPC Nanodiscs; 4) in contrast to some previous work, POPC only interacts weakly with Ca2+; 5) divalent cations interact with lipids in a lipid- and ion-specific manner for POPA and PIP2 lipids; and 6) the monovalent anion type has little influence on the lipid charge. These results should help eliminate inconsistencies among data obtained using different techniques, membrane systems, and experimental conditions, and they provide foundational data for developing an accurate view of membranes and membrane-protein interactions.

Kinetic Behavior of Salmonella on Low NaNO2 Sausages during Aerobic and Vacuum Storage.

This study evaluated the growth kinetics of Salmonella spp. in processed meat products formulated with low sodium nitrite (NaNO2). A 5-strain mixture of Salmonella spp. was inoculated on 25-g samples of sausages formulated with sodium chloride (NaCl) (1.0%, 1.25%, and 1.5%) and NaNO2 (0 and 10 ppm) followed by aerobic or vacuum storage at 10℃ and 15℃ for up to 816 h or 408 h, respectively. The bacterial cell counts were enumerated on xylose lysine deoxycholate agar, and the modified Gompertz model was fitted to the Salmonella cell counts to calculate the kinetic parameters as a function of NaCl concentration on the growth rate (GR; Log CFU/g/h) and lag phase duration (LPD; h). A linear equation was then fitted to the parameters to evaluate the effect of NaCl concentration on the kinetic parameters. The GR values of Salmonella on sausages were higher (p<0.05) with 10 ppm NaNO2 concentration than with 0 ppm NaNO2. The GR values of Salmonella decreased (p<0.05) as NaCl concentration increased, especially at 10℃. This result indicates that 10 ppm NaNO2 may increase Salmonella growth at low NaCl concentrations, and that NaCl plays an important role in inhibiting Salmonella growth in sausages with low NaNO2.

Effect of Electrolyte Concentration on the Stern Layer Thickness at a Charged Interface.

The chemistry and physics of charged interfaces is regulated by the structure of the electrical double layer (EDL). Herein we quantify the average thickness of the Stern layer at the silica (SiO2 ) nanoparticle/aqueous electrolyte interface as a function of NaCl concentration following direct measurement of the nanoparticles' surface potential by X-ray photoelectron spectroscopy (XPS). We find the Stern layer compresses (becomes thinner) as the electrolyte concentration is increased. This finding provides a simple and intuitive picture of the EDL that explains the concurrent increase in surface charge density, but decrease in surface and zeta potentials, as the electrolyte concentration is increased.

Effect of Electrolyte Concentration on the Stern Layer Thickness at a Charged Interface

AbstractThe chemistry and physics of charged interfaces is regulated by the structure of the electrical double layer (EDL). Herein we quantify the average thickness of the Stern layer at the silica (SiO2) nanoparticle/aqueous electrolyte interface as a function of NaCl concentration following direct measurement of the nanoparticles’ surface potential by X‐ray photoelectron spectroscopy (XPS). We find the Stern layer compresses (becomes thinner) as the electrolyte concentration is increased. This finding provides a simple and intuitive picture of the EDL that explains the concurrent increase in surface charge density, but decrease in surface and zeta potentials, as the electrolyte concentration is increased.

Power Generation from Concentration Gradient by Reverse Electrodialysis in Dense Silica Membranes for Microfluidic and Nanofluidic Systems

In this study, we investigate power generation by reverse electrodialysis in a dense silica membrane that is between two NaCl solutions with various combinations of concentrations. Each silica membrane is fabricated by depositing a silica layer on a porous alumina substrate via chemical vapor deposition. The measured potential-current (V-I) characteristics of the silica membrane are used to obtain the transference number, diffusion potential, and electrical resistance. We develop empirical correlations for the transference number and the area-specific resistance, and present the results of power generation by reverse electrodialysis using the fabricated silica membranes. The highest measured power density is 0.98 mW/m2. In addition, we develop a contour map of the power density as a function of NaCl concentrations on the basis of the empirical correlations. The contour map shows that a power output density of 1.2 mW/m2 is achievable with the use of silica membranes and is sufficient to drive nanofluidic and microfluidic systems. The dense silica membrane has the potential for use in micro power generators in nanofluidic and microfluidic systems.

Effect of NaCl Salts on the Activation Energy of Excited-State Proton Transfer Reaction of Coumarin 183

Coumarin 183 (C183) was used as a photoacid to study excited-state proton transfer (ESPT) reactions. Here, we studied the effect of ions on the ESPT of C183 in aqueous NaCl solutions using a steady-state fluorescence spectroscopy and time-correlated single photon counting (TCSPC) method. The acid dissociation equilibrium of excited-state C183 and the activation energy for the ESPT of C183 were determined as a function of NaCl concentration. The change in the equilibrium constant was found to be correlated with the solvation energy of deprotonated C183. Frequency-resolved TCSPC signals measured at several temperatures were analyzed by using a global fitting analysis method which enabled us to extract all the rate constants involving the ESPT reaction and the spectra of individual species. The activation energy for the ESPT reaction of C183 was highly dependent on NaCl concentration. Quantum chemical calculations were used to calculate the local hydrogen-bond (H-bond) configurations around C183 in aqueous NaCl solutions. It was found that the activation energy for the ESPT was determined by the local H-bond configurations around C183 which were significantly influenced by the dissolved ions.

Salting-out and salting-in: competitive effects of salt on the aggregation behavior of soy protein particles and their emulsifying properties.

Emulsions stabilized by protein particles have gained increasing research attention due to their combined advantages of biocompatibility and superior stability. In this study, colloidal particles consisting of soy protein isolates (SPIs) prepared through a heat-treatment procedure are used to make oil-in-water emulsions at a protein concentration of 10 g L(-1) and a pH of 5.91. We investigate parallelly the effects of NaCl on the stability and rheological properties of the particle suspensions and their stabilized emulsions at salt concentrations of 0, 100 and 400 mM. The aggregation behavior of the particles is strongly dependent on the NaCl concentration, showing signs of sedimentation at low NaCl concentration (100 mM) but redispersion again at high NaCl concentration (400 mM). The extensive particle aggregation is beneficial to the formation of a continuous interfacial film for the emulsions, and hence results in a remarkable increase of creaming stability and interfacial viscoelastic moduli. The results can be explained in terms of two competitive effects of NaCl: salting-out and salting-in, which are attributed to complex electrostatic interactions between the particles as a function of NaCl concentration. The delicate balance between salting-out and salting-in provides an interesting insight into the nature of underlying protein particle interactions in aqueous suspensions and a possible mechanism for tailoring their emulsifying properties via salt effects.

Effect of Lipid Content on Saltiness Perception: A Psychophysical Study

AbstractThe objective of this study was to evaluate the effect of oil addition (10, 20 and 40% of oil in water) on saltiness perception as a function of NaCl concentration. A sensory panel (n = 20) was selected from the local community and trained to taste saltiness intensity using magnitude estimation. Data obtained were fitted to the Stevens’ power law. As expected, saltiness intensity increased as [NaCl] in the aqueous phase ([NaCl]aq) increased, for a constant type of sample. All types of samples (0, 10, 20 and 40% oil‐in‐water emulsions) were well fitted to the Stevens’ power law with exponent values of 0.87, 0.76, 0.66 and 0.47 for the 0, 10, 20 and 40% oil‐in‐water emulsions, respectively. This is the first research that reports exponential values for saltiness perception in the presence of an oil phase. This research also shows that saltiness perception is driven by a combination of processes that include [NaCl]em and the presence of an oil phase.Practical ApplicationsThis research contributes to the understanding of the effect of oil addition on saltiness perception for a range of NaCl concentration. This knowledge will help food scientist in the development of foods with reduced amount of sodium while maintaining the sensory properties of their product.