KCI, CaCI2, Na+ Binding, and Salt Taste of Gum Systems

Aqueous nonionic (0.3% w/v) and ionic (0.1% and 0.3% w/v) gum systems containing NaCl, or equal weights of NaCl plus KCl, or NaCl plus CaCl, were examined. At equivalent molar concentrations of added ions, ²³Na NMR transverse relaxation rates (R₂, set^?1) showed an increase in average Na⁺ mobility with the addition of K⁺ or Ca²⁺ to ionic gum systems. Correspondingly, salt taste increased with addition of KCl as determined by Decision Boundary modeling of subject identification data. Viscosity did not affect saltiness. Na⁺ was free to induce salt taste when K⁺ was bound to the gum. Enhancement of salt taste by KCl is due, in part, to competitive binding of Na⁺ and K⁺ in a system.     

Thickening Agents Effects on Sodium Binding and Other Taste Qualities of Soup Systems

Low sodium chicken broth with NaCl added to provide Na⁺ concentrations in typical reduced Na⁺ soups (144 and 288 mg Na⁺/240 mL serving) was thickened with commonly used gum, starch, or flour food additives. Xanthan gum suppressed saltiness as the result of ionic binding of Na⁺, as determined by sensory evaluation and ²³Na NMR spectroscopy. Saltiness was affected by added NaCl (p = 0.0001), thickener (p < 0.01), and added NaCl* thickener (p < 0.01), and positively correlated with chicken and overall flavors (p = 0.0001). Cornstarch provided body, no suppression of salt taste, and the greatest salt enhancement of chicken and overall flavors. In complex food systems, temperature and other factors affected Na⁺ binding as measured by NMR pointing to the need for a new model.     

Taste Qualities of Reduced-Sodium Soups as Affected by Serving Temperature

Reduced-sodium chicken broths (144 mg Na⁺ and 288 mg Na⁺/240 mL serving) were thickened with commonly used food ingredients (four gums, two starches and flour). Salt taste of most soups was stable to temperature change(room, 22°C vs serving, 60–65°C) as judged by 12 subjects. However, soups made with potato starch (144 mg Na⁺) and ionic xanthan and sodium carboxymethylcellulose gums (288 mg Na⁺) were saltier at room than at serving temperature. Salt taste enhanced chicken and overall flavors. Soups prepared with all-purpose wheat flour remained unchanged in viscosity, but other soups were perceived as thicker at room temperature.     

Fat, Protein, and Mineral Components of Added Ingredients Affect Flavor Qualities of Tomato Soups

Ten tomato soups were prepared with deionized, distilled water, skim or whole milk, or deionized, distilled water with added fat (corn oil), protein (calcium caseinate), and/or minerals (NaCl, KCl, CaCl₂) to equal the composition of whole milk. Tomato soups prepared with whole or skim milk were perceived as sweetest by a sensory panel of 12 trained subjects. Salt taste was probably masked by sweetness from lactose in milk. Added minerals may have increased saltiness either by adding to total Na⁺ content or by freeing Na⁺ from other ingredients making it more available for perception. Saltiness was suppressed by added protein, which increased pH, and may have affected Na⁺ binding. Salt taste intensity correlated positively with tomato flavor.     

Enhanced Sweetness in Sweetener-NaCI-Gum Systems

Enhancement of sweetness in aqueous gum (0.03%, w/v) sweetener systems by added NaCl (0.05%, w/v) was evaluated by a sensory panel. ²³Na NMR spectroscopy was used to determine Na⁺ binding and its relationship to sweetness elicited by glucose, lactose, maltose, sucrose and aspartame. Sweetness intensity differed due to gum (p = 0.0001) and sweetener (p = 0.0001), but was not affected by NaCl (p = 0.0774). Sweetness increased with added NaCl in xanthan, guar and locust bean gum solutions. However, sweetness decreased in k-carrageenan systems possibly due to endogenous cation (Ca²⁺, K⁺ and Na⁺) content, which influences Na⁺ mobility. The sweetest systems containing lactose and/ or xanthan, showed the greatest enhancement by NaCl.     

1H and 23Na NMR Relaxation Studies of the NaCl/β-Lactoglobulin System Equilibrated at Various Water Activities

NMR relaxation times (T₁) of ¹H and ²³Na were determined at 8, 14, 60, MHz and at 14, 52 MHz, respectively, in the NaCl/β-lactoglobulin system equilibrated at water activities ranging from 0.11 to 0.97. A two-state model was used for both nuclei which allowed the calculation of proportions of bound and free species. It was shown that bound water and Na⁺ increased at medium water activities in the presence of increasing NaCl. The discrepancy with adsorption isotherms data was explained by (1) limitations of the mass balance equation used to calculate interacting salt by gravimetry and (2) the fact that NMR probed the totality of ions in the vicinity of the protein, whereas adsorption isotherms were indicative of sodium choride tightly bound to the protein. It was also shown that the protein and Na⁺ shared available water molecules at medium and low water activity.     

The chemical composition and some physical properties of a water-soluble gum from Prosopis africana seeds

A water‐soluble gum was extracted from the endocarp capsule of the seed coat of Prosopis africana. The gum yield varied substantially with the method of dehulling. Maximum yield was obtained after boiling in 0.1 m Na₂CO₃ for 4 h. The effects of two different gum concentrations on the rheological properties of gum solutions were examined. The gum formed viscous solutions at low concentrations and exhibited stable viscosity in the pH range 6.0–8.0. Chemical analyses showed that the purified gum had a composition of 2.4% fat, 1.04% protein, 21.5% crude fibre and a gelation concentration of at least 10%. Galactose and mannose were the major polysaccharides identified. Large reductions in viscosity were observed with the addition of various concentrations of Na⁺ salts. The activation energies of flow for 2 and 3% gum solutions were in the range of 19.2–22.8 kJ mol^?1 and were characteristic of systems with little intra‐ and intermolecular interactions.     

Effects of Ca++, Mg++ and Na+ on Heat Aggregation of Whey Protein Concentrates

Effect of Ca⁺⁺ on the heat aggregation of whey protein concentrates (WPC) was compared with that of Na⁺ and Mg⁺⁺. On the alkaline side of the isoelectric zone, aggregation of WPC was increased by the addition of CaCl₂, MgCl₂ or NaCl, among which CaCl₂ showed the greatest effect. The denaturation temperature of WPC determined by differential scanning calorimetry significantly decreased in the presence of CaCl₂ or MgCl₂, but increased slightly in the presence of NaCl. In the electrophoretic patterns of heated WPC, the most sensitive protein to Ca⁺⁺ was β-lactoglobulin.     

Relationship between sensory saltiness intensity and added oil in low-viscosity and high-viscosity polymer solutions

Generally, the foods we usually eat are not only aqueous solutions, but also viscous solutions and solids. Therefore, it is interesting for us to explore how taste components are perceived in a viscous polymer solution. The relationship between the sensory evaluation of saltiness intensity, amount of added oil, and apparent viscosity was clarified in low-viscosity and high-viscosity polymer solutions. The study was conducted using samples containing corn oil, sodium chloride, and [xanthan gum] or [xanthan gum + locust bean gum] as a thickener. Oil was added to the viscous polymer solutions regardless of whether they were low- or high-viscosity, and saltiness intensity was evaluated as compared with a reference solution. The low-viscous polymer solutions with [xanthan gum] were perceived to be saltier than the high-viscous polymer solutions with [xanthan gum + LBG] as the amount of oil increased. The shear stress value gradually increased as the amount of oil increased in both the low-viscosity and the high-viscosity polymer solutions, as derived from the fluid constitutive equation. There was a correlation between saltiness intensity and apparent viscosity in both high- and low-viscosity polymer solutions. A coefficient of determination (R²) of 0.918 was obtained between saltiness intensity and “apparent viscosity” for the samples using [xanthan gum] and that of 0.683 between saltiness intensity and “apparent viscosity” for the samples using [xanthan gum+LBG]. The low-viscosity polymer solutions showed a saltier intensity as the amount of oil increased and a greater correlation with apparent viscosity, as compared with the high-viscosity polymer solutions.     

Characterization of sodium mobility,binding, and apparent viscosity in full-fat and reduced-fat model emulsion systems

Reduction of sodium in foods is a top priority in today’s food industry. However, sodium reduction, due to its vital importance as a tastant, as well as its contribution to many other food properties, is no simple task. This study investigated the mobility of sodium ions, the ionic binding of sodium ions to xanthan gum, a popular functional hydrocolloid used in many processed foods, and the effect of sodium ions on the apparent viscosity of full-fat and reduced-fat model emulsion systems with increasing concentrations of added sodium, ranging from 0 to 480 mg added sodium per 30 g serving. ²³Na NMR spectroscopy was utilized to measure sodium ion mobility, determined by both longitudinal (T₁) and transverse (T₂) relaxation times, and sodium binding, expressed by the ratio of bound to total sodium peak areas as the sodium concentration in the system increased. It was found that apparent viscosity increased, then decreased with increasing sodium concentration, and the concentration at which apparent viscosity began to decrease was higher for the reduced-fat compared to the full-fat emulsion system. The sodium mobility and sodium binding did not seem to be directly affected by pH. The characterization of sodium mobility, binding, and apparent viscosity in full-fat and reduced-fat model emulsion systems provides a foundation upon which further effects of sodium binding and functionality, including saltiness perception, in food matrices can be investigated.     

Rheological behaviors of hydroxypropylated sweet potato starches influenced by guar,locust bean,and xanthan gums

This study examined the steady flow and dynamic rheological behaviors of hydroxypropylated sweet potato starch (HPSPS) pastes mixed with guar gum (GG), locust bean gum (LBG), and xanthan gum (XG) at different concentrations (0, 0.3, and 0.6%). The HPSPS–gum mixtures had higher shear‐thinning fluid characteristics than the control (0% gum) at 25°C. The addition of the gums resulted in an increase in the consistency index (K) and apparent viscosity (η_a,100). The dynamic moduli (G′, G″) and complex viscosity (η*) values of the HPSPS–gum mixtures were higher than those of the control, and they increased with an increase in gum concentration. In particular, the presence of XG at 0.6% in the HPSPS–gum mixture systems gave rise to the greatest viscoelastic properties among the gums examined at different concentrations. The tan δ (ratio of G″/G′) values (0.35–0.57) of the HPSPS–GG and HPSPS–XG mixtures were much lower than those of the control (0.82) and HPSPS–LBG (0.88–1.06), indicating that the elastic properties in the HPSPS–gum mixture systems were strongly affected by the additions of GG and XG. These steady flow and dynamic rheological parameters indicated there were synergistic interactions between the HPSPS and gums. The synergistic effects of the gums and modified starch were hypothesized by considering the molecular incompatibility and molecular interactions between the gums and HPSPS.     

Studies on the rheological properties and functional potentials of achi (Brachystegea eurycoma) and ogbono (Irvingia gabonesis) seed gums

Water soluble gums were extracted from seeds of achi (Brachystegea eurycoma) and Ogbono (Irvingia gabonesis). The rheological properties of each gum were studied at temperatures from between 10–70°C at 1.0, 1.5, 2.0, and 2.5% concentrations. The effects of small quantities of the gums on some of the quality characteristics of an ice cream mix were investigated. These characteristics were compared with those of some commercial food gums, carboxymethyl cellulose (CMC), Kappa carrageenan (KCA), and sodium alginate (SA). The viscosities of both gums were time-independent and Ogbono seed gum (OSG) appeared to be more pseudoplastic than Achi seed gum (ASG). The pseudoplastic nature was not affected by increasing temperature. The temperature control was more critical for OSG (E_a. 20.2 MJ mol⁻¹) than ASG (E_a 13.9 MJ mol⁻¹) during processing. The viscosity behaviour of ASG indicates that it may be a highly branched polysaccharide. The overrun, viscosity, shapefactor and meltdown values of the ice cream, when ASG was added as stabilizer, were 95%, 0.035 PaS, 72% and 32%, respectively. Values for OSG were 70%, 0.025 PaS, 65% and 37.7%, respectively. Only values for the ASG cream fell within the ranges of values obtained for the commercial gums. ©     

Bound Cations in Cucumber Pickle Mesocarp Tissue as Affected by Brining and CaCl2

The effects of brining, fermentation, storage, time of CaCl₂ addition and concentration of NaCl and CaCl₂ on Ca⁺⁺, Mg⁺⁺, Na⁺, and K⁺ bound to middle lamella-cell wall material of cucumber pickle mesocarp tissue were examined. Changes in the amount of each bound cation occurred rapidly during the first 2 days of brining; levels then remained relatively stable during fermentation and storage if concentrations of NaCl or CaCl₂ in brines were not altered. NaCl reduced levels of bound Ca⁺⁺, Mg⁺⁺, and K⁺, and the presence of CaCl₂ increased the amount of bound Ca⁺⁺ by displacing the other cations. Delayed addition of CaCl₂ to brines enhanced the content of bound Ca⁺⁺, indicating that levels of bound Ca⁺⁺ may not be related to maintenance of firmness.     

The Effects of Different Gums and Their Interactions on the Rheological Properties of a Dairy Dessert: A Mixture Design Approach

In this study, the steady and dynamic rheological properties of the dairy dessert samples (puddings) containing carrageenan, alginate, guar and xanthan gums and their combinations were investigated in a model system, and mixture design was utilized to observe the effects of the gums and their interactions. The flow behaviour of the pudding samples fitted to the Ostwald de Waele model (R ²?>?0.98). All the samples exhibited a gel structure with their higher G′ (storage modulus) values than the G″ (loss modulus) values. Carrageenan was the most effective hydrocolloid on both the steady and dynamic rheological parameters of the dairy dessert samples. On the other hand, alginate had relatively smaller effect. Furthermore, 30 pudding samples containing different gum or gum combinations were classified into two groups (A and B) by using principal component analysis (PCA). Samples containing more than 33% carrageenan in their formulations made up the group A which positively correlated to K (consistency index), η ₅₀ (apparent viscosity at shear rate 50 s^?1), G′, G″, G* (complex modulus) and η* (complex viscosity) values.     

Compositional analysis and rheological characterization of gum tragacanth exudates from six species of Iranian Astragalus

The sugar composition and viscoelastic behaviour of Iranian gum tragacanth exuded by six species of Astragalus was investigated at a concentration of 1.3% and varying ionic strength using a controlled shear-rate rheometer. Compositional analysis of the six species of gum tragacanth by high-performance anion-exchange chromatography with pulsed amperometric detection suggested the occurrence of arabinose, xylose, glucose, galactose, fucose, rhamnose and galacturonic acid residues in the gum structure; however, the proportions of each sugar varied significantly among the gums from the different species of Astragalus, and this variation led to interesting differences in functional properties. Rheological measurements performed on dispersions of the six species of gum tragacanth demonstrated viscoelastic properties. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated that the different gum tragacanth dispersions had distinctive viscoelastic behaviours. Investigation of the viscoelastic properties of the different gum dispersions in the presence of NaCl revealed that the addition of NaCl could lead to slight to drastic decreases in the G′, G″ or η^∗ values of the various gums. In general, the results indicated that the six varieties of gum tragacanth studied exhibited significantly different rheological properties; therefore, these different gums may find use in a variety of applications as stabilisers, thickeners, emulsifiers and suspending agents depending on their rheological behaviour.     

Structural features of a xylogalactan isolated from Hymenaea courbaril gum

The gum from Hymenaea courbaril (Caesalpiniaceae) produced gum at seed level. The gum is soluble in water, dextrorotatory and less viscous than the gum from Cyamopsis tetragonolobus (guar gum). The polysaccharide, isolated from this gum, contains galactose, glucose, xylose and arabinose. The preparation of degraded products by acid hydrolysis and Smith-degradation process led to obtain degraded gums A and B, and the polysaccharides I and II. Chemical methods in combination with 1D NMR (¹H, ¹³C, DEPT-135) and 2D NMR (COSY, HMQC and HMBC) were applied. The backbone is a xylogalactan; β-d-galactose and β-d-xylose residues are 4-O- and 2-O-linked, respectively. The branches are constituted by xylose, arabinose and galactose. It was also observed 4,6-di-O-substituted galactose residues. This work shows interesting structural features of the polysaccharide isolated from H. courbaril gum.     

Factors influencing permeability of the cell membrane of the osmotolerant yeast Saccharomyces rouxii grown in the presence and absence of 18% NaCl. I. Na+/K+-activated Mg2+-dependent ATPase

It was found that cells of Saccharomyces rouxii contain an ouabain-inhibited ATPase, assumed to be an Na⁺/K⁺-activated Mg²⁺-dependent ATPase, which could serve as a sodium pump protecting the cells in a high salt environment. Twenty-two cell homogenates or supernatants (centrifuged at 3000 × g) grown without added salt in the medium contained sufficient total ATPase activity to liberate (on average) 0.225 μM P_i min^?1 mg^?1 protein. The percentage of total ATPase inhibited by the addition of ouabain (1 × 10^?4 M) varied from 7 to 100%. Cell homogenates or supernatants from cells grown in the presence of 18% NaCl in the media contained sufficient ATPase activity to liberate (on average) 0.114 μM P_i min^?1 mg^?1 protein, about 50% of the total ATPase activity found in the non-salt grown cells. The percentage of total ATPase activity inhibited by ouabain ranged from 16 to 100%. Although the non-salt-grown cells contained approximately double the total ATPase activity of the salt-grown cells. there was evidence that the percentage of total ATPase that is ouabain sensitive (Na⁺/K⁺-activated ATPase) is higher in the salt-grown cells. Also, cells of S. rouxii grown in media without added NaCl, recovered by centrifugation and transferred to media containing 18% NaCl for 16 h and again recovered by centrifugation, homogenized and centrifuged at 10 000 × g contained 61.2% ouabain-sensitive ATPase compared with 21.3% ouabain-sensitive ATPase in the cells before adaptation to the high salt environment.     

Dispersive Ability of Carboxylated Cellulose Nanofibrils for Aqueous Monolayer Montmorillonite Dispersion: Influence of Na+ and Ca2+ Concentrations

Carboxylated cellulose nanofibrils (CNFs) have emerged as effective green dispersants for monolayer montmorillonite (MMT) dispersions. However, their dispersion capability is sensitive to the metal ion concentration in aqueous solutions. Hence, this study investigated the effects of Na⁺ and Ca²⁺ concentrations on the dispersive ability of carboxylated CNFs for monolayer MMTs in water. Quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) were utilized to explore the interfacial interactions between the carboxylated CNFs and monolayer MMTs under different Na⁺ and Ca²⁺ concentrations. When the concentration of Na⁺ reached 0.1 mmol/L, the adhesion mass of carboxylated CNFs on MMT-coated wafer peaked at 24.47 mg/m², higher than control sample (carboxylated CNF-dispersed monolayer MMT dispersion without metal ions, 16.03 mg/m²). Moreover, the electrostatic shielding effect promoted a better dispersion of monolayer MMTs by carboxylated CNF dispersant. With a further increase in the Na⁺ concentration, the surface charge of CNFs and MMTs would be reversed resulting from the improved electrostatic shielding effect, which weaken the dispersive ability of carboxylated CNFs. The addition of Ca²⁺ reduced the dispersive ability of carboxylated CNFs for monolayer MMTs, because Ca²⁺ required a lower concentration for the onset of charge reversal compared to Na⁺. This study provides interfacial scale insights into the influence of metal ion concentration on carboxylated CNF-dispersed monolayer MMT dispersions. It also provides a strategy to enhance the dispersive ability of carboxylated CNFs for monolayer MMTs.     

Correlation of Proton T1 with Polymer and Solute Waters in Starch-Sucrose Mixtures

Proton pulsed NMR methodology was applied to correlate the observed spin-lattice (T₁) and spin-spin (T₂) relaxation times with the amount of water associated to sucrose (SOL) and that to starch (POL) in a sucrose-starch model system containing both. Sucrose, starch and four mixtures were equilibrated to four water activities (a_w, 0.86-0.97). Calculations for T₂ were invalid due to an undeterminable amount of molecular diffusion caused by field inhomogeneity in the magnet. Model equations were developed for calculating SOL and POL from T₁ and a_w; These values showed high correlations (R²>0.97) with SOL and POL as determined from sorption data for sucrose and starch. This validated the use of this instrument with the mathematical models developed.     

Aerobic Counts, Color and Adenine Nucleotide Changes in CO2 Packed Refrigerated Striped Bass Strips

Hybrid striped bass (HSB) strips were dipped in chlorine or distilled water and packaged in 60% CO₂, 6% O₂, and 34% N₂ (MAP) or in AIR. APC reached 10⁸ CFU/g after 4 days for AIR and 10 days for MAP fish. Sensory panelists detected a whiter color flesh in fish treated with chlorine. Hypoxanthine increased while IMP decreased and ADP and ATP did not change throughout. If inosine was excluded in the predictor, a modified K value (K*) could be applicable as a freshness indicator of freshwater HSB but storage environment should be specified. K* values correlated highly with APC for AIR (R²= 0.84) and MAP packs (R²= 0.85).