Analysis of the rat chorda tympani nerve response to "super salty" sodium carbonate

In behavioral experiments, rats perceive sodium carbonate (Na2CO3) as super salty. In fact, when the dissociated Na+ ions are accounted for, rats perceive Na2CO3 as 5× saltier than equinormal concentrations of NaCl. The chorda tympani nerve (CT) responds to salts through at least two receptor mechanisms and is a model system for understanding how salt taste is transmitted to the brain. Here, we recorded CT nerve activity to a broad range of NaCl (3-300 mM) and Na2CO3 (3-300 mN) to investigate why Na2CO3 tastes so salty to rats. Benzamil, a specific epithelial sodium channel (ENaC) antagonist, was used to determine the relative contribution of apical ENaCs in Na2CO3 transduction. The benzamil-insensitive component of CT nerve responses was enhanced by increasing the adapted tongue temperature from 23°C to 30°C. Na2CO3 solutions are alkaline, so we compared neural responses (with and without benzamil) to 100 mM NaCl alone (6.2 pH) and at a pH (11.2 pH) that matched 100 mN Na2CO3. As expected, NaCl responses increased progressively with increasing concentration and temperature. Responses to 3 mN Na2CO3 were greater than 3 mM NaCl with and without benzamil, but the shape of the first log-fold range of was relatively flat. Adjusting the pH of NaCl to 11.2 abolished the thermal enhancement of 100 mN NaCl through the benzamil-insensitive pathway. Rinsing Na2CO3 off the tongue resulted in robust aftertaste that was concentration dependent, thermally sensitive, and benzamil-insensitive. Responses to alkaline NaCl did not recapitulate Na2CO3 responses or aftertaste, suggesting multiple transduction mechanisms for the cations (2Na+) and anion (CO3-2).

The Effect of Steviol Glycosides on Sensory Properties and Acceptability of Ice Cream

There has been a challenge in overcoming the bitter aftertaste of stevia, a natural non-caloric sweetener. Recent research focuses on investigating various types of steviol glycosides, the sweet compounds in stevia leaves, as they exhibit different sensory characteristics. This study determined the sensory properties and acceptability of ice cream sweetened solely with three steviol glycosides, rebaudioside (Reb) A, D, and M (0.09% w/v), using sucrose-sweetened ice cream as a control (14% w/v). Ice cream consumers (n = 92) rated their overall liking, attribute liking, and sweetness and bitterness intensities and described the aftertastes of each sample using check-all-that-apply. The liking scores of Reb D- and M-sweetened ice creams were significantly higher than those of Reb A-sweetened ice cream. Among the three glycosides, only Reb M showed a sweetness intensity comparable with that of sucrose. Consumers perceived the aftertastes of Reb D and M ice creams as being more sweet, pleasant, creamy, and milky, while Reb A was more artificial and chemical. Reb D and M ice creams were also plotted close to sucrose in the correspondence analysis graph, meaning that their aftertaste characteristics were similar to those of sucrose. The present study clearly highlights that Reb D and M have better tastes and provide better perceptions to consumers than Reb A, which is the most widely used glycoside in food industry.

Consumer-Based Sensory Characterization of Steviol Glycosides (Rebaudioside A, D, and M)

Rebaudioside (Reb) D and M are the recent focus of the food industry to address the bitter taste challenge of Reb A, which is the most commonly used steviol glycoside in natural sweetener stevia. This study evaluated the sensory characteristics of Reb A, D, and M, compared to 14% (w/v) sucrose, using a consumer panel and explored the relationship between 6-n-Propylthiouracil (PROP) taster status (i.e., non-tasters, medium tasters, supertasters) and the perceived intensity of sweet and bitter tastes of the three steviol glycosides. A total of 126 participants evaluated the intensities of in-mouth, immediate (5 s after expectorating), and lingering (1 min after expectorating) sweetness and bitterness of 0.1% Reb A, D, M, and 14% sucrose and described the aftertaste of the sweeteners by using a check-all-that-apply (CATA) question. The results showed that in-mouth sweetness and bitterness of Reb D and M were not significantly different from sucrose, unlike Reb A which showed significant bitterness. However, Reb D and M showed more intense lingering sweetness than sucrose. The CATA analysis resulted that Reb D and M were closer to positive attribute terms and also to sucrose than Reb A, but Reb D and M were still considered artificial, which may cause them to be perceived negatively. When comparing among PROP taster groups, no significant differences in the perceived sweetness and bitterness of the three steviol glycosides were found. This study generates important information about Reb A, D, and M for the food industry, especially working with products formulated to deliver reductions in sugar using a natural high-intensity sweetener, stevia.

Effect of Protein-Lipid-Salt Interactions on Sodium Availability in the Mouth and Consequent Perception of Saltiness: In Solutions

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.

Effect of Protein-Lipid-Salt Interactions on Sodium Availability in the Mouth and Consequent Perception of Saltiness: As Affected by Hydration in Powders

There is a broad need to reformulate lower sodium food products without affecting their original taste. The present study focuses on characterizing the role of protein-salt interactions on the salt release in low-moisture systems and saltiness perception during hydration. Sodium release from freeze-dried protein powders and emulsion powders formulated at different protein/lipid ratios (5:0 to 1:4) were characterized using a chromatography column modified with a porcine tongue. Emulsion systems with protein structured at the interface were found to have faster initial sodium release rates and faster hydration and were perceived to have a higher initial salt intensity with a lower salty aftertaste. In summary, exposure of the hydrophilic segments of the interface-structured proteins in emulsions was suggested to facilitate hydration and release of sodium during dissolution of low-moisture powder samples.

Suppression of umami aftertaste by polysaccharides in soy sauce

Umami is one of 5 basic tastes that make foods savory and palatable. The umami aftertaste is a long-lasting taste sensation that is important for Japanese broth (dashi) utilized for various Japanese foods. Soy sauce is usually added when making dashi-based dishes; however, different soy sauces produce distinct effects on the umami aftertaste. In this study, we attempted to identify the substances that cause the suppression of the umami aftertaste in soy sauce by combining sensory analysis, size fractionation, chemical analysis, and enzymatic treatment. The suppressive substance was revealed to be polysaccharides with molecular weights between 44900 and 49700. The results of acid hydrolysis and enzymatic treatment suggested that the polysaccharides were cellulose. These results indicate that a type of water-soluble cellulose derived from soybean, wheat, or microorganisms has a suppressive effect on the umami aftertaste of soy sauce. Future studies should focus on developing a strategy that regulates the amount of these polysaccharides generated during soy sauce production, to maintain or enhance the umami aftertaste.