NaCl Diffusion Research Articles

Dual mode diffusion and sorption of sodium chloride in surimis under cooking conditions

Diffusion and sorption behaviors of NaCl in surimis prepared from Pacific cod (Gadus morhua), red sea bream (Pagrus major) and big-eye tuna (Thunnus obesus) were studied. The variations of Fick’s diffusion coefficients, D, of NaCl with respective maxima and of almost linear sorption isotherms were consistently interpreted with the dual mode diffusion and sorption theory. Good linear correlations were found between the concentrations of Langmuir mode sorption site, Sa, of NaCl (R2=0.993) and also thermodynamic diffusion coefficient of the Langmuir species, DT(L), of NaCl (R2=0.950), with charged amino acid contents in the surimis. The facts that Sa and DT(L) are related to the concentration of charged site suggest that the sites gather in a certain region, the water content of which becomes high with the site concentration.

A mathematical model of the effect of pH and food matrix composition on fluid transport into foods: An application in gastric digestion and cheese brining

The question of bioaccessibility of nutrients within a food matrix has become of increasing interest in the fields of nutrition and food science as bioaccessibility is the precursor to bioavailability. By analyzing the propagation of the wetting front of acidic water in raw carrot core and Edam cheese as model systems, we show that the diffusion of the acidic water is dependent on the pH of the gastric fluid and the food matrix. In addition, we demonstrate that the diffusion of NaCl during cheese brining is also dependent upon the concentration of the NaCl. This demonstrates that Fickian diffusion, along with a concentration dependent diffusion coefficient, is a valid model for describing concentration profiles in multiple food systems.Utilizing the diffusion rates found at various pH levels (1.50, 2.00, 3.50, 4.30, 5.25 and 7.00), we developed a model to describe the measured non-linear rate of soluble solid loss during digestion at various constant pH levels. Additionally, we have developed a model to predict the likely rate of soluble solid loss during digestion in the stomach where pH decreases with time. This model can be used to help understand and optimize the relationship between food structure/composition and food degradation in the human stomach, which may help in the development of novel foods with desired functionality.

Detailed Mathematical Analysis of Solute Transport in Armfield's Liquid Diffusion Apparatus

AbstractA solute's diffusivity is a key property in the design and analysis of mass transfer systems. A simple method to determine such coefficients in aqueous media is Armfield's diffusion apparatus, in which reservoir (donor) and bath (receiver) compartments are separated by a honeycomb array of liquid‐filled cylindrical pores. The solute of interest, i.e., NaCl, diffuses from the reservoir and pores into the bath. The electrical conductivity of the bath solution, which is proportional to the NaCl molarity, is tracked as a function of time at constant temperature. A comprehensive mathematical model is presented which combines simultaneous solute transport in the three compartments, allowing estimation of the aqueous NaCl diffusivity from experimental data. The model improves existing theoretical analyses of such data and can be adapted to study other challenging systems.

Dual mode sorption and diffusion of NaCl in foodstuffs containing liquid water

Dual mode sorption and diffusion of NaCl in foodstuffs containing liquid water

Doping and Diffusion in an Extruded Saloplastic Polyelectrolyte Complex

Doping constants and diffusion coefficients for an extruded, stoichiometric, dense polyelectrolyte complex, PEC, were determined for a Hofmeister series of anions. These thermodynamic and kinetic parameters describe the extent and speed to which a complex of poly(styrenesulfonate) and poly(diallyldimethylammonium) may be doped. Both parameters followed a Hofmeister ordering and covered a wide range of response. Differences between doping and undoping kinetics were observed, with the latter adhering well to classical diffusion from the cylindrical geometry employed. Tracer diffusion of radiolabeled Na+, compared with coupled diffusion of NaCl, revealed slightly faster diffusion of Na+ compared to Cl– ions within the PEC.

Changes in Morphology and Ionic Transport Induced by ALD SiO2 Coating of Nanoporous Alumina Membranes

Nanoporous anodic alumina membranes (NPAMs) were produced by the two-step anodization method in sulphuric, oxalic and phosphoric acidic electrolytes displaying a hexagonally ordered spatial arrangement of pores with well controlled nanopore size distribution and low porosity. Some selected NPAMs were further modified by conformal coating their surface and inner pore walls with a thin layer of SiO2 by means of atomic layer deposition (ALD), which reduces both the pore radii and porosity but it also seems to affect to the electric fixed charge on the membranes surface. A comparative study about the influence of silica modification of NPAMs surfaces on the ionic transport through the nanoporous membranes has been performed by measuring membrane potentials and electrochemical impedance spectroscopy with NaCl solutions. According to these results, a direct correlation between the membrane effective fixed charge and the NaCl diffusion coefficient can be established. The coating with a SiO2 thin layer causes a reduction of 75% in the positive effective fixed charge of the NPAMs independently of their pore radii and the increase in counterion transport (cation transport number and diffusion coefficient) even through constrained nanopores, which can be of interest in several applications (microfluidics, drug delivery, nanofilter devices, etc.). Moreover, slight changes in the membrane/solution interface due to the SiO2 cover layer are also indicated.

NaCl diffusion kinetics in dry salting of goat cheese

With the aim of studying diffusion during the dry salting of goat cheese, the experimental profiles of salt and water concentrations were determined in terms of time and distance from the interface. The effective diffusion coefficient was determined using Fick’s Second Law for a semi-infinite model. NaCl was not present at distances greater than 2cm from the interface after 24h of salting. The moisture profiles were seen to decrease from the surface farthest from the interface to the zone in contact with the salt. In contrast, salt concentrations were highest at the interface and decreased with distance from this point. The value of the effective diffusion coefficient did not vary significantly with distance from the interface, but did decrease significantly with salting time. Essentially the same phenomenon of salt incorporation was found to occur in dry salting as in brining.

Effects of charged groups in foodstuffs on diffusion of NaCl in the foodstuff substrate

Effects of charged groups in foodstuffs on diffusion of NaCl in the foodstuff substrate

Estimation of NaCl diffusivity by computed tomography in the Semimembranosus muscle during salting of fresh and frozen/thawed hams

In the elaboration of dry-cured hams, the understanding of salt diffusion is an important step to optimise salt uptake. Calibrated computed tomography (CT) gives non-destructive measurements of salt and water contents. The aim of this study is to develop a simplified methodology based on an unidirectional diffusion model and CT measurements for assessing salt diffusion in Semimembranosus muscle (SM) during salting of ham. Five pork carcasses were selected according to the SM muscle pH (5.8 ± 0.1), 24 h post mortem, and hams weight (12.7 ± 0.5 kg). One ham from each pair was subjected to a freezing/thawing treatment before salting period. CT images of a central section were taken in each ham during the 16 days of the salting period. From each voxel, NaCl and moisture mass fractions were determined and introduced in the diffusion model. Thus, NaCl apparent diffusion coefficients were calculated for each ham. Resulting diffusion coefficients are in the same order of magnitude than values given by literature. As expected, 30% higher diffusion coefficients were found for frozen/thawed hams samples. Combination of calibrated CT measurements with a simple diffusion model can be used to obtain a non-destructive estimation NaCl apparent diffusivity during dry-curing of ham.

Applications of Low-voltage Ohmic Process Combined with Temperature Control System to Enhance Salting Process of Pork

This study investigated the effects of a low-voltage ohmic heating process (2.5 and 3.8 V/cm) on the thawing characteristics and NaCl diffusion of pork. The thawing rate of pork was dependent on the applied voltages and brine salinities, and few differences were obtained in pork quality parameters (color, water-holding capacity, and shear force) regarding the different treatments. The NaCl concentration of pork after ohmic thawing was higher than that following brine-immersion thawing, however, the NaCl diffusion did not differ from when fresh meat was immersed in brine. For application of the ohmic process in fresh pork, various ohmic pulses were generated in order to prevent the meat from overheating, and the results indicated that the ohmic process was a better way to enhance NaCl diffusion compared with immersing pork at high temperature. Although the mechanisms involved in NaCl diffusion at low-voltage electric field strength were unclear, the present study demonstrated that the ohmic process has a potential benefit in the application of meat processing.

Dual Mode Diffusion and Sorption of Sodium Chloride in Pre-Cooked Potato (Solanum tuberosum L.)

For cooked potato, we report maximum showing variations of the Fick’s diffusion coefficients, <em>D</em>, of NaCl with total salt concentration, <em>C</em><sub>t</sub>, in the foodstuff in the temperature range, 30-98°C. The variations were successfully explained with the dual mode diffusion and sorption theory, which has been successfully applied to the diffusion of NaCl in cooked Japanese radish, solidified egg white, and pork meats. The original theory (Komiyama & Iijima, 1974) was revised by changing the definitions of the parameters for the presence of liquid water droplets in the foodstuffs. The sorption isotherms, being found to be almost linear with very slight concave upward curvatures, were explained by invoking the presence of the droplets. Two thermodynamic diffusion coefficients, <em>D</em><sub>T</sub>(p) and <em>D</em><sub>T</sub>(L), of NaCl of the partition and Langmuir type sorption species, respectively, in the diffusion rate determining region were estimated for the temperature range. The temperature dependences were found to show definite rises in the range of 50-70°C, suggesting the presence of a transition in the diffusion environment.

Functionalized Lipid Nanoparticles–Cellophane Hybrid Films for Molecular Delivery: Preparation, Physicochemical Characterization, and Stability

Lipid nanoparticles functionalized with the sunscreen 2,4‐dihydroxybenzophenone (FLNPs) have been prepared by the ultrasound method and embedded in highly hydrophilic cellophane supports (regenerated cellulose, RC), creating biocompatible hybrid films (RC‐FLNPs samples). The morphology of the FLNPs was studied with transmission microscopy, whereas the surface and interior chemical composition was analyzed by micro‐Raman spectroscopy. RC‐FLNPs hybrid films were prepared from the immersion of two cellophane supports with different thicknesses and water uptake properties (RC‐3 and RC‐6) in an aqueous dispersion of FLNPs. The structure of this hybrid material was visualized with bright‐field microscopy, which clearly showed the inclusion of the FLNPs in the cellophane matrix. The stability of the RC‐FLNPs films with respect to both aqueous environments and time was demonstrated by NaCl diffusion measurements. The reduction in the diffusion coefficient through the nanoparticle‐modified films compared with the original supports confirms the presence of nanoparticles for concentration gradients of up to 0.4M (osmotic pressure around 10 bar), indicating the stability of the hybrid hydrophilic material, even in aqueous environments and under matter flow conditions for a period of 21 days. © 2011 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4815–4822, 2011

Effect of Lysozyme Proteins on the Mutual-Diffusion Coefficient of Sodium Chloride in Water

We measured accurate NaCl main-term diffusion coefficients in aqueous lysozyme solutions at 25 °C and pH 4.5 using the Gosting diffusiometer operated in its Rayleigh interferometric optical mode. The dependence of this diffusion coefficient on lysozyme concentration was examined using the obstruction-effect theory. Agreement between experimental results and theory is achieved if lysozyme proteins are treated as hydrated spheres with a hydration number of 240, a value that is comparable with those reported in literature for this protein. Electrostatic interactions and common-ion effects due to lysozyme net charge at pH 4.5 do not contribute significantly to the behavior of the NaCl diffusion coefficient within our experimental range of salt concentrations [(0.25 to 0.90) mol·dm–3].

Temperature effect on transport parameters and structure of regenerated cellulose membranes

The effect of annealing temperature (25 °C < T < 97 °C) on transport and structural parameters for two different regenerated cellulose membranes (dense and nanoporous) is studied. Results show different temperature dependence for water permeability and NaCl diffusion coefficient depending on the membrane structure, with an increase from 25 °C to 60 °C and a more significant reduction between 70°°C and 97 °C for the dense sample, but practically constant for the nanoporous. These results seem to be directly related to the membrane’s elastic behaviour according to the temperature effect on degree of swelling. Moreover, diffusional permeability-concentration curves also allow the determination of other membrane parameters (fixed charge concentration and partition coefficient) which are independent of temperature.

The Synthesis and Characteristic Properties of Poly (AAc-Co-AAm)

The copolymers of 10% acrylic acid (AAc) and 90% acryl amide (AAm) were synthesized by free radical polymerization with 5% ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The basic physical feature such as density, fixed charge density, average molecular weight, equilibrium water contentment and crosslink density were studied. In this investigation, the equilibrium and kinetic experiments were performed under three different ionic strengths, the equilibrium behavior of the hydrogels was characterized by varying the designed stimulus and by measuring the weight of hydrogel disc using a high accuracy balance. The ionic strength of the solution was adjusted with NaCl and the buffer solution was phosphoric acid. Potentiometric titration was performed to investigate the quantity of dissociated H+. Last, diffusion coefficients of aqueous sodium chloride in water swollen cross-linked poly (AAc-co-AAm) membranes were studied. A self-planned cell was used for the measurement of NaCl diffusion coefficients.

Structural, chemical surface and transport modifications of regenerated cellulose dense membranes due to low-dose γ-radiation

Modifications caused in commercial dense regenerated cellulose (RC) flat membranes by low-dose γ-irradiation (average photons energy of 1.23 MeV) are studied. Slight structural, chemical and morphological surface changes due to irradiation in three films with different RC content were determined by ATR-FTIR, XRD, XPS and AFM. Also, the alteration of their mechanical elasticity has been studied. Modification of membrane performance was determined from solute diffusion coefficient and effective membrane fixed charge concentration obtained from NaCl diffusion measurements. Induced structural changes defining new and effective fracture propagation directions are considered to be responsible for the increase of fragility of irradiated RC membranes. The same structural changes are proposed to explain the reduction of the membrane ion permeability through a mechanism involving either ion pathways elongation and/or blocking.

Use of sodium nitrite in salt-curing of Atlantic salmon ( Salmo salar L.) – Impact on product quality

Quality changes during processing and quality differences in smoked fillets of Atlantic salmon (4–5 kg) salted with nitrite salt compared to table salted fillets were measured. Quality parameters from right-side fillets dry salted with nitrite salt were compared with the respective left-side fillets treated the same way with table salt. Ten raw right-side fillets were analysed and used as raw material reference. Use of nitrite salt in salt-curing of smoked salmon affected colour to a more reddish hue, tended to increase carotenoid stability and displayed positive effects on NaCl diffusivity. Only slight weight changes and change in texture properties were revealed. The use of nitrite salt displayed no adverse effects like increased content of N-nitrosoamines in smoked products. In fact, significant lower contents of N-nitrosoamines were found in nitrite salted smoked fillets compared to smoked fillets salted with table salt. Relatively high amounts of residual nitrite in nitrite-treated fillets seem to be the most prominent adverse effect caused by the use of nitrite salt in salt-curing of smoked Atlantic salmon.

Acrylamide Mitigation in Potato Chips by Using NaCl

In April 2002, Swedish researchers shocked the world when they presented preliminary findings on the presence of acrylamide in fried and baked foods, most notably potato chips and French fries, at levels of 30–2,300 ppb. The objective of this research was to study the effect of immersing potato slices in a NaCl solution over the acrylamide formation in the resultant potato chips. Potato slices (Verdi variety, diameter 40 mm, width 2.0 mm) were fried at 170 °C for 5 min (final moisture content of ∼2.0%). Prior to frying, the potato slices were treated in one of the following ways: (1) control slices (unblanched or raw potato slices); (2) slices blanched at 90 °C for 5 min in water; (3) slices blanched at 90 °C for 5 min plus immersed in a 1 g/100 g NaCl solution at 25 °C for 5 min; (4) slices blanched at 90 °C for 5 min plus immersed in a 3 g/100 g NaCl solution at 25 °C for 5 min; (5) slices blanched at 90 °C for 5 min plus immersed in distilled water at 25 °C for 5 min; and (6) slices blanched at 90 °C for 5 min in a 3 g/100 g NaCl solution. Blanching followed by the immersion of potato slices in 1 g/100 g NaCl solution was effective in reducing acrylamide content in ∼62%; however, almost half of this percentage (∼27%) could be attributed to the effect of NaCl and 35% to the effect of the slight heating treatment during salt immersion step (25 °C for 5 min). Blanching seems to make the NaCl diffusion in potato tissue easier leading to a significant acrylamide reduction in the potato slices after frying.

Salt and Aroma Compound Release in Model Cheeses in Relation to Their Mobility

Physicochemical properties (partition and diffusion coefficients) involved in the mobility and release of salt and aroma compounds in model cheeses were determined in this study. The values of NaCl water/product partition coefficients highlighted interactions between proteins and NaCl. However, these interactions were not modified by the product composition or structure. On the contrary, model cheese composition and structure influenced NaCl diffusion and both partition and diffusion for aroma compounds. Analysis of in-nose measurements of aroma release during eating, with regard to physicochemical properties, showed that product and aroma properties partly contributed to flavor release. Depending on the model cheese composition, structure and firmness, physicochemical properties, food breakdown, and chewing behavior can lead to different aroma release profiles. Finally, a discussion of all the results with regard to salt and flavor perception of the model cheese showed that both physicochemical and cognitive mechanisms contributed to perception.

Dual mode diffusion and sorption of sodium chloride in pork meats under cooking conditions

This study aims to obtain insight into mechanisms of NaCl diffusion in pork meats under cooking conditions: the loins at 5 (raw), 63 (pre-cooked) and 98 °C (pre-cooked), the mince at 98 °C (pre-cooked), and the filet at 98 °C (pre-cooked). It has been generally presumed that NaCl in any of pork meats diffuses with a constant Fick's diffusion coefficient, D, through liquid water channel imbibed in them. However in the present study, we experimentally obtained skewed bell shape variations of D in all of the above meats with respective maxima at certain low NaCl concentrations. These variations were interpreted in terms of a dual mode sorption and diffusion theory, which had been successfully applied to NaCl diffusion behaviors in Japanese radish and solidified egg white. This interpretation gives a thermodynamic diffusion coefficient, DT(p) for the partition species of NaCl and another one, DT(L) for the Langmuir type sorption species, both in the water swollen substrates in the meats. It was found that DT(p) values are sizably smaller than corresponding DT(L) values. This difference was ascribed to the lower water content in the p region than that in the L region. With the two DTs and additional equilibrium parameters, the theory explained the remarkable decrease of D value with C at 21 °C found by Guiheneuf et al. and nearly constant D values in the higher C range at 5 °C reported by other researchers. Experimentally obtained sorption isotherms of NaCl, which were slightly convex upward in the low C range, were satisfactorily reproduced with the parameters and the fractions of water swollen substrates in the whole meats.