Effect of Protein–Lipid–Salt Interactions on Sodium ... - ACS Publications

Aug 10, 2015 - Samples with increased protein were rated as having significantly lower initial saltiness and a higher salty aftertaste. However, when ...
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Effect of Protein−Lipid−Salt Interactions on Sodium Availability in the Mouth and Consequent Perception of Saltiness: In Solutions Umut Yucel†,§ and Devin G. Peterson*,§ †

Food Engineering Department, Middle East Technical University, Ankara, Turkey Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota 55108, United States

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ABSTRACT: The influence of protein−sodium interactions on the availability of sodium in the aqueous phase of liquid samples and consequently on the perception of saltiness was investigated. The aqueous effluents of casein and casein emulsion−salt solutions were monitored for sodium availability from a tongue column system. In the aqueous protein−salt solutions, increasing the protein/salt ratio from 1:1 to 5:1 or 10:1 significantly decreased the initial salt concentration in the effluent and resulted in a higher salt concentration in the effluent over time. Sensory analysis was in agreement. Samples with increased protein were rated as having significantly lower initial saltiness and a higher salty aftertaste. However, when casein was formulated as an emulsion, the initial release of sodium in the effluent was enhanced (compared to nonemulsified protein). Increasing the emulsion interfacial area (more hydrophilic segments of the protein were structured into the aqueous phase) resulted in a higher salt concentration in the aqueous phase and greater perceived saltiness intensity. In summary, protein interactions, specifically ionic, were reported as food interactions that influence salt perception and provide a basis to develop higher flavor quality low-sodium food products. KEYWORDS: salt reduction, protein−salt ionic interactions, emulsions, aftertaste, sensory

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as calcium caseinate, xanthan, and κ-carrageenan gums, can bind sodium ions to limit the salty taste perception, whereas nonionic gums do not have such an effect in tomato soups.5 In contrast, Lauverjat et al. reported that casein and NaCl interactions can change the localization and mobility of the salt in low-fat cheese, but with less effects on its perception.8 Moreover, the change in the protein composition during fermentation of cheese-like products can further affect the salt interactions with other constituents and, therefore, its perception.9 The presence of fat can further complicate the perception of taste-active molecules. For example, bitterness in foods and pharmaceutical formulations often decrease with increasing fat levels due to their largely hydrophobic nature and decreased aqueous concentrations.10,11 Conversely, hydrophilic salt molecules are largely insoluble in fat. Increasing fat concentrations in a food formulation will result in higher aqueous concentrations of salt, which can increase the perceived salty taste.12,13 However, there are contradictory findings regarding the effect of fat concentration on salt perception in the literature, probably because transport kinetics also play an important role in determining the salt perception. Some researchers have claimed that lipid coating on the tongue surface can limit the molecular diffusion of the sodium ions to their respective channels, causing a decrease in the perception of salty taste.4,14,15 In addition to the bulk phase effects, the size of fat droplets or their destabilization has also been reported to modulate salt delivery profiles via interfacial interactions and

INTRODUCTION Salt as sodium chloride (NaCl) is one of the most commonly used food ingredients to increase the palatability of food products. However, excess sodium intake is often associated with increased risk of high blood pressure related cardiovascular diseases.1 There is therefore a broad need to control sodium consumption and to formulate reduced-salt products without sacrificing the flavor quality. There are different approaches to formulating reducedsodium food products. Manufacturers have utilized nonsodium salts as alternatives (e.g., KCl) as well as umami compounds to enhance the palatability of low-sodium products (e.g., using small peptides such as monosodium glutamate, MSG); however, such changes in product formulation can result in undesirable tastes.2,3 An alternative approach is to enhance the salt perception by controlling the delivery properties of sodium via intermolecular interactions. In general, the extent of perceived saltiness is directly related to the amount of sodium ions that can reach ion channels on the tongue. Salt perception is known to increase with NaCl concentration (typical S-shaped psychometric function) and also with its mobility.4,5 In parallel, Busch et al. claimed that pulsed delivery of salt can be used to enhance the salt taste perception, whereas le Reverend et al. suggested that this mechanism is significant only for largely viscoelastic products.6,7 In a complex food environment, salts and biopolymers, such as proteins, interact with each other to modify transport properties of sodium. Although the nature of these interactions is largely ionic and predictable to an extent via empirical approximations (e.g., Hofmeister series), there are conflicting findings reported in the literature regarding the effects of biopolymers on salt perception. For example, Rosett et al. showed that sodium and negatively charged biopolymers, such © XXXX American Chemical Society

Received: May 8, 2015 Revised: August 5, 2015 Accepted: August 9, 2015

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Journal of Agricultural and Food Chemistry their adsorptivity on the surface of a tongue.16−20 This retention of fat on the tongue can cause residual taste perception (i.e., aftertaste) of flavor compounds that they are interacting but to varying extents.21 In this study a systematic approach was used to mechanistically understand the relationship between salt release behavior and perception as affected by biopolymer−salt interactions. The objectives of this study were to specifically evaluate the extent of protein−salt interactions at different solution concentrations and to characterize interfacial effects when biopolymers are structured around nanoscale lipid droplets on salt transport and perception. We modified a chromatography column with a porcine tongue to simulate salt transport in the mouth. Analytical results for salt transport and adsorptivity were then correlated with sensory evaluation to elucidate the mechanisms controlling the perception of saltiness in such colloidal systems. In the subsequent paper we investigated the effects of lipid−protein−salt interactions on the hydration rate, and subsequent salt release, from lowmoisture (i.e., freeze-dried) samples.

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MATERIALS AND METHODS

Materials. Sodium caseinate (Na-cas) and sodium chloride (NaCl) (USP grade) were both purchased from Sigma-Aldrich (St. Louis, MO, USA). Corn oil was purchased from a local supermarket. The porcine tongues were obtained from the meat laboratory at the University of Minnesota (St. Paul, MN, USA). In all sample preparations and experiments, sodium-free nanopure water was used. In house deionized water was further purified by using a Barnstead Nanopure Diamond water purification system (Thermo Scientific, Dubuque, IA, USA) to obtain nanopure water. Protein solutions (0−10 wt %) were prepared by overnight stirring in nanopure water at room temperature. Emulsions at different protein/lipid ratios were prepared using a hot homogenization technique.22 Briefly, hot protein solutions (1−5 wt %) were mixed with corn oil (0−20 wt %) using a high-speed blender to form a coarse emulsion. The emulsion premix was then passed through a microfluidizer (M-110Y Microfluidizer, Microfluidics, Newton, MA, USA) at ca. 60−65 °C (3 passes at 1200 bar). After the samples cooled to room temperature, salt was added and stirred for 4−5 h. Analytical Measurements. Salt adsorptivity and retention on a model tongue surface were evaluated by using a modified gel permeation chromatography column accompanied by a porcine tongue (Figure 1). The front section of the fresh porcine tongue was cut as a disk (2.1 cm in diameter and 0.2−0.3 cm in thickness) and kept frozen at −20 °C until used. The thawed tongue pieces were then placed on the bottom plunger surface covering the base. Then, aliquots of samples (ca. 0.15 mL) were added to the tongue surface, and the top plunger was adjusted to about 0.1−0.2 cm above the tongue, leaving a negligible amount of empty space above the tongue surface. Salted protein solutions and oil-in-water emulsions were then washed from the tongue surface using an HPLC system (Shimadzu 10A series, Columbia, MD, USA) with nanopure water at a rate of 5 mL/min. The effluent was collected at 1 min intervals by a fraction collector. Each fraction was analyzed for sodium concentrations using an atomic absorption spectrometer (AAS) (PerkinElmer Inc., Waltham, MA, USA) coupled with a K−Na lumina hallow cathode lamp (PerkinElmer Inc.) and for dissolved solids using an evaporative light scattering detector (ELSD) (PL-ELSD 2100 Ice, Agilent, Santa Clara, CA, USA). The fractions from the column effluent were diluted in water to be within the dynamic range of the instrument. The ELSD was calibrated using reference dispersions with various protein and lipid concentrations similar to that measured for the sample fractions. Particle Size Measurements. The average hydrodynamic diameter of the emulsions was determined by dynamic light scattering. The samples were diluted to ca. 1:100 with nanopure water, and then the particle size was analyzed using a Delsa Nano C Particle Analyzer

Figure 1. Picture of the chromatography column modified to work with circular porcine tongue (2.1 cm) and coupled to an HPLC system. (Beckman, Brea, CA, USA). The measurement was performed at 25 °C and at a 165° scattering angle. Mean hydrodynamic diameter was calculated on the basis of size distribution by weight, assuming a lognormal distribution. Ten individual size measurement runs were performed, with each run recording 100 size events. The droplet size (i.e., Sauter mean diameter) of the emulsions was found to be 0.2 μm. Sensory Analysis. A trained descriptive analysis panel of 11 panelists evaluated the salty intensity of the samples. Panelists were trained on a 15-point intensity scale, with NaCl reference solutions at 0.2, 0.35, 0.5, 0.64, and 0.75% corresponding to intensity scores of 2.5, 5, 8.5, 12, and 15, respectively. The panelists were trained during 12 1h sessions over a period of 3 weeks. The performance of the panelists was assessed using blind references during training. Samples were evaluated in triplicate using a randomized block design. Four samples were evaluated each session. The samples were served in 20 mL plastic cups, coded in random three-digit codes. During the sample evaluation the panelists were instructed to pour 10 mL of sample onto their tongue, hold for 5 s, and then expectorate the sample back into a container (time zero for aftertaste analysis) for further analysis of the residual sodium. Panelists rated the saltiness aftertaste intensity at 0, 15, 30, 60, 120, 180, 240, and 300 s after expectorating the sample. Panelists waited 10 min between samples. Water and unsalted crackers were used as palate cleansers. Panelists were classified into two groups on the basis of their rating of saltiness intensity after rinsing their mouth with a 1% salt solution and waiting 1 min prior to evaluation. High and low saliva flow rates were classified for those who rated saltiness at 2 at 1 min after sample introduction, respectively. B

DOI: 10.1021/acs.jafc.5b02311 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

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Journal of Agricultural and Food Chemistry Statistical Analysis. Results were evaluated for statistical significance using a t test for a pairwise comparison of two samples at α = 0.05. All samples were prepared and analyzed in triplicate.

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RESULTS AND DISCUSSION It is known that the salty taste of food is produced by the transduction of the sodium ions via epithelial sodium channels, albeit all of the cellular mechanisms related to the perception of saltiness are still under investigation.23 To taste sodium ions they need to be released from the food to be adsorbed on the surface of the tongue to start electrochemical signaling producing the sensation of saltiness. However, during consumption food products typically have very short retention time in the oral cavity, limiting the available sodium contributing to the salty taste. In a food matrix such ions can interact with other larger molecules, especially biopolymers (e.g., proteins), via electrostatic interactions, and as a result affect their transport kinetics and retention on the surface of the tongue. In the current study our goal was to focus on the nature of interactions between protein and salt molecules affecting the transport kinetics of salt ions in aqueous solutions and, in turn, mechanisms that influence salt perception. The delivery profile of sodium in protein−salt solutions was initially investigated using a tongue surface in a modified chromatography column coupled to an HPLC system (Figure 1). As the first step, we validated the performance of the designed tongue−column system to study the transport kinetics of sodium. Simple aqueous solutions of sodium chloride (0.5−10 wt %) were injected onto the column−tongue system, and the adsorptivity of sodium on the tongue surface was monitored from the effluent (Figure 2). The first data point in the sodium concentration versus time graph corresponds to the sodium concentration in the first fraction of the effluent (0−1 min). The linear relationship reported between the initial concentrations of the salt solutions and the sodium concentrations in the first fraction collected from the tongue−column system indicated that this design was working as expected, and therefore it was deemed suitable to study the transport kinetics of sodium. The rate of sodium removal from the tongue’s surface was very fast, being quantitatively depleted within 2 min. In the next step, we investigated the effects of dissolved protein on sodium retention on the tongue’s surface. Three protein−salt solutions consisting of 1, 5, and 10% protein at a constant 1% NaCl level were made using sodium caseinate, the sodium salt of the major protein in milk. The intrinsic levels of sodium in sodium caseinate were negligible with regard to the amount of NaCl added to the samples. It is highly soluble in water and often used in low-fat product formulations. Addition of the protein was predicted to bind the sodium ions via electrostatic interactions and change the availability of sodium to the aqueous phase during consumption and subsequently alter salt perception. The sodium concentration in the aqueous effluent as monitored from the model tongue system (Figure 1) for the three protein solutions is shown in Figure 3. As seen in Figure 3a, the sodium concentrations in the first minute of the effluent decreased with increasing protein concentrations, specifically for the 5 and 10% protein solutions. The release of sodium in the effluent for the 1% protein solution was similar to that for the pure salt solution (no protein), indicating there were not sufficient protein interactions at this dosage level to alter the initial salt amount washed off the tongue system. Protein−salt interactions largely depend on the anionic charged segments of the

Figure 2. Sodium concentrations in the effluent after (a) 0.5% (diamonds) and 1% (circles) salt solutions and (b) 5% (triangles) and 10% (squares) salt solutions were washed from the model tongue surface (5 mL/min) as collected in fractions at 1 and 2 min intervals (13−30 min). The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

available protein and would increase with higher concentration of protein in these solutions (i.e., higher protein/salt ratio) as well as with the charge potential of the proteins. After this initial minute, the higher protein samples reported higher sodium concentrations in the effluent over time (Figure 3b). For example, from 1 to 4 min the amount of sodium in the effluent was approximately 2 times higher for the 5 and 10% protein solutions in comparison to the 1 or 0% protein solutions. The increased release of sodium over time from the higher protein solution could be explained by protein adhesion to the tongue’s surface that would serve as a salt reservoir and release sodium over time into the aqueous phase. Other researchers have also reported salt perception was influenced by polymer−salt interactions based on various mechanisms. Rosett et al. showed that the charge on the biopolymer was more important to determine the perception of salty taste, rather than the viscosity.5 Oral processing has also been reported to modify food−tastant interactions. For example, it has been shown that saliva amylase can break down large starch molecules, decreasing the apparent viscosity of the solutions but also the mixing efficiency, which limits the molecular diffusion of salt and reduces the salt perception.24 De Jongh and Janssen reported the retention time of liquid foods in the oral cavity increased when the viscosity was increased (by protein and carbohydrate addition) and likewise altered taste perception.20 The noted influence of the protein/salt ratio on the sodium transport behavior in Figure 3 could potentially be confounded by the change in the sample solids content on molecular diffusion. C

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calculated assuming pseudo-first-order kinetics for the fractions between 1 and 6 min (i.e., keff was calculated from the slope). Similarly, keff was not statistically different for 10% (0.81 s−1) and 5% (0.82 s−1) protein solutions at the same protein/salt ratio (10:1), although the solution thicknesses were different. However, when the salt concentration in the 5% protein solution was increased to a protein/salt ratio of 5:1 (1% salt, Figure 3), both the sodium concentration change in the first fraction (1.31 ± 0.02%) and the keff (0.86 s−1) were significantly larger than for the 10:1 ratio. These findings indicate viscosity effects from the protein added to the solutions were not an important factor that influenced the difference in salt delivery reported between the 5 and 10% protein solutions in Figure 3 and supported protein ionic binding as an important mechanism of salt delivery. The extent of ionic protein−salt interactions would be governed by the accessibility of the ionic groups to the aqueous phase. To investigate this concept, protein−salt interactions in emulsion systems were characterized using casein and oil colloid systems. When oil is emulsified with caseinate, the hydrophilic protein segments (volume fraction is about 0.9) surround the outside of the oil droplets as a dense outer layer that is approximately 1 nm in thickness, whereas a diffuse hydrophobic segment (volume fraction is about 0.1) forms an inner layer in the oil droplet that can extend up to 10 nm in thickness.25 Moreover, proteins on these lipid droplets are known to have a net negative charge around neutral pH (i.e., pH above their isoelectric point).26 It has been shown that such interfacial structures of caseinate can affect the distribution profiles of small molecules and cause localization around the droplets’ interface.22 This electrostatic charge around the droplets could further affect the rate of ion exchange between the aqueous phase and the droplet surface. For example, the oxidation of protein-stabilized omega-3-enriched oil-in-water emulsions can be inhibited at pH below the pI of proteins (i.e., due to cationic properties of the emulsion droplets).27,28 In a similar manner, the net negative charge around the droplet can attract cationic sodium ions and serve to enhance the localization of sodium ions around the charged outer layer segments of the caseinate molecules on the lipid droplets. The release of sodium from the aqueous emulsion systems is illustrated in Figure 5. Two different emulsion formulations of 1% protein−4% lipid and 2.5% protein−2.5% lipid were compared to a 5% protein aqueous solution and a aqueous salt solution, all at 1% salt. The sodium concentration in the first fraction of the effluent (0−1 min) was significantly reduced for the emulsion systems compared to the 5% protein solution, even though the percent protein levels in the emulsions were comparatively lower in amount. Additionally, the emulsion with 4% lipid and 1% protein reported a lower salt concentration (at 0−1 min) compared to the 2.5% lipid and 2.5% protein emulsion. Although the emulsion systems had a lower percent protein, when the lipid amount increased relative to the percent protein, a higher interfacial area is expected that ultimately enhanced the exposure of the anionic groups in the aqueous phase and thus the ionic interactions with sodium. The release of sodium from the emulsion systems from 1 to 14 min is further shown in a magnified view in Figure 5b and showed similar trends as Figure 3b. Samples that lowered the salt concentration the most in the first minute had the highest release of sodium after this first minute, in this case the 1% protein−4% lipid sample.

Figure 3. (a) Sodium concentrations in the effluent of 1% salt solutions containing 0% (circles), 1% (triangles), 5% (squares), and 10% (diamonds) casein after washing from the model tongue surface (5 mL/min) as collected in fractions at 1 min intervals. (b) The dashed area from the top graph was zoomed for better resolution from 1 to 15 min. The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

To further ascertain if changes in the solids content affected the sodium release profiles in Figure 3, sodium release was monitored from two protein solutions at 5 and 10% that were formulated at the same protein/salt ratio of 10:1 (Figure 4).

Figure 4. Sodium concentrations in the effluent of 0.5% salt solutions containing 0% (diamonds) and 5% (triangles) casein and 1.0% salt solutions containing 0% (circles) and 10% (squares) casein after washing from the model tongue surface (5 mL/min) as collected in fractions at 1 min intervals. The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

For both the 5 and 10% protein solutions the decreases in sodium concentration in the first fraction (0−1 min) relative to the corresponding salt solution were effectively the same (p > 0.05). The sodium concentrations reported in the first fractions for the 5 and 10% were significantly smaller (p > 0.05) and 1.39 ± 0.03 and 1.42 ± 0.02 times less than the corresponding pure salt solutions. An effective diffusivity (keff) constant was also D

DOI: 10.1021/acs.jafc.5b02311 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

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emulsified droplets. The higher retained sodium was then washed off the tongue surface at a higher rate over time. On the basis of the observed influence of protein on the retention of salt and corresponding higher amounts of salt released over time (compared to aqueous salt) in the model tongue column (Figures 3 and 5), the protein material was suggested to adhere to the tongue’s surface and function as a salt reservoir and release salt with continued washing. To further examine the interaction of the protein in the tongue column, the total solute concentration in the effluent was also measured from 0 to 14 min by using an ELSD, and the data are shown in Figure 7. Review of the solute concentration in the

Figure 7. Total solute concentration in the effluent of emulsions after washing from the model tongue surface (5 mL/min) as collected in fractions at 1 min intervals and analyzed by evaporative light scattering detector. Samples consisted of 1% salt solution (circles), 1% protein− 4% lipid (diamonds), 2.5% protein−2.5% lipid (triangles), and 5% protein−0% lipid (squares). The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

Figure 5. (a) Sodium concentrations in the effluent of emulsions (5% organic phase) compared to that of the 1% salt solution (circles) after washing from the model tongue surface (5 mL/min) as collected in fractions at 1 min intervals. The emulsified phase was formulated as 1% protein−4% lipid (diamonds), 2.5% protein−2.5% lipid (triangles), or 5% protein−0% lipid (squares). (b) The dashed area from the top graph was zoomed for better resolution for fractions between 1 and 14 min. The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

effluent over time confirmed our previous statement that the organic phase (i.e., protein) adhered to the tongue’s surface. In parallel, the highest absorptivity (i.e., slowest diffusivity) was observed for the emulsions with the highest lipid concentrations. Consequently, this supported οur statement that the protein material functioned as a reservoir of sodium that released sodium over time into the aqueous phase. Sensory descriptive analysis of the salt intensity was further conducted on the protein−salt solutions (Figure 8) as well as the emulsion systems (Figure 9) to extrapolate the analytical data to human perception. For the sensory evaluations, the panelists were classified into two groups, low and high saliva flow rates. For the protein solution (Figure 8), the sensory data were in agreement with analytical results (Figure 3). With increasing protein content of the salt solutions, a lower salt intensity rating was reported for the initial time period with a corresponding higher salt intensity afterward (aftertaste). For example, in the low saliva flow regimen, the salty taste of the salt solution (no protein) disappeared within 120 s, whereas there was still a residual salty taste lingering after 180 s for the 10% casein solution. Although the salty ratings in both groups with high and low saliva flow rates followed the same trend, the time−salt intensity curves more clearly separated at the low saliva flow regimen. Therefore, we further discussed the sensory ratings of this group for the emulsion samples. The presence of colloidal lipid considerably changed the perception of saltiness (Figure 9). Interestingly the initial intensities of the emulsions at a constant 5% organic content were not significantly different (p < 0.05) from that of the 1% salt solution itself (Figure 9a) in contrast to the analytical data

To further single out the interfacial effects of emulsions on sodium interactions (i.e., as a function of surface area and number of droplets), sodium release rates from emulsions with the same protein content (5%) and different lipid concentrations (5 and 20 wt %) at 1% salt were compared (Figure 6). Similar results were obtained; the droplet surface area increased (by increasing the lipid content) and the initial release rate decreased. Therefore, the electrostatic interactions between protein and salt molecules were enhanced by conferring the anionic properties of the proteins to the aqueous phase of the

Figure 6. Sodium concentrations in the effluent of emulsions stabilized with 5% casein and containing 5% (diamonds) or 20% (squares) lipid, after washing from the model tongue surface (5 mL/min) as collected in fractions at 1 min intervals. The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis. E

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(Figure 5a). The nanoscale dimensions of lipid droplets may have facilitated sodium availability on the tongue’s surface. However, increasing the lipid concentrations caused higher salt intensity aftertaste, which was in line with the analytical data (Figure 5b). Emulsion samples with the same amount of protein (5%) at two lipid concentrations (5 and 20%) were compared for their time course salt intensity behaviors (Figure 9b). The sensory results followed the same trend as the analytical data (Figure 4): increasing the number of lipid droplets provides more interface for proteins, further enhancing the salt−protein interactions and resulting in longer salty aftertaste. In this study, we showed that protein−salt interactions could play an important role in determining the transport properties of sodium in solutions. We designed an analytical system to study sodium retention on a tongue surface and compared the results to sensory analysis. Overall, our data supported the importance of intermolecular interactions (i.e., electrostatic interactions) in determining the perception of salty taste. These results can serve as a guideline to control sodium availability, and subsequently its perception, when food products are formulated for lower sodium content while enhancing salt perception. In the following paper, we studied the effect of protein−salt interactions on the salt perception and the hydration rates of low-moisture samples as a function of lipid levels.

Figure 8. Time−intensity plot for salty intensity rating of 1% salt solutions containing 0% (circles), 1% (triangles), 5% (squares), and 10% (diamonds) casein for (a) low saliva flow rates and (b) high saliva flow rates. The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

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AUTHOR INFORMATION

Corresponding Author

*(D.G.P.) E-mail: [email protected]. Phone: (612) 624-3201. Fax: (612) 625-5272. Funding

This research was supported by the Flavor Research and Education Center, Department of Food Science and Nutrition, University of Minnesota. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Cutler, J. A.; Follmann, D.; Allender, P. S. Randomized trials of sodium reduction: an overview. Hypertension 1997, 65, 643S−651S. (2) Kilcast, D.; Angus, F. Reducing Salt in Foods: Practical Strategies; Woodhead Publishing: Boca Raton, FL, USA, 2007. (3) Osborn, S. Salt reduction innovations. World Food Ingred. 2013, April/May, 18−20. (4) Phan, V. A.; Yven, C.; Lawrence, G.; Chabanet, C.; Reparet, J. M.; Salles, C. In vivo sodium release related to salty perception during eating model cheeses of different textures. Int. Dairy J. 2008, 18, 956− 963. (5) Rosett, T. R.; Kendregan, S. L.; Klein, B. P. Fat, protein, and mineral components of added ingredients affect flavor qualities of tomato soups. J. Food Sci. 1997, 62 (1), 190−193. (6) Busch, J. L. H. C.; Tournier, C.; Knoop, J. E.; Kooyman, G.; Smit, G. Temporal contrast of salt delivery in mouth increases salt perception. Chem. Senses 2009, 34, 341−348. (7) Le Reverend, B. J. D.; Norton, I. T.; Bakalis, S. Modelling the human response to saltiness. Food Funct. 2013, 4, 880−888. (8) Lauverjat, C.; Deleris, I.; Trelea, I. C.; Salles, C.; Souchon, I. Salt and aroma compound release in model cheeses in relation to their mobility. J. Agric. Food Chem. 2009, 57, 9878−9887. (9) Lemieux, L.; Simard, R. E. Bitter flavor in dairy products. I. A review of the factors likely to influence its development, mainly in cheese manufacture. Lait 1991, 71, 599−636. (10) Roy, G. General ingredient or process approaches to bitterness inhibition and reduction in oral pharmaceuticals. In Modifying

Figure 9. Time−intensity plot for salty intensity rating of 1% salt emulsions for samples formulated as (a) 5% total organic phase containing 1% protein−4% lipid (diamonds), 2.5% protein−2.5% lipid (triangles), 5% protein−0% lipid (squares), 1% salt solution (circles) and (b) 5% protein with 5% lipid (diamonds) or 20% lipid (squares). The bars on the data show standard deviation. The straight lines between data points are merely used to aid in visual analysis.

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DOI: 10.1021/acs.jafc.5b02311 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.jafc.5b02311 J. Agric. Food Chem. XXXX, XXX, XXX−XXX