Application Of Taste Dilution Analysis Research Articles

All-trans-Configuration in Zanthoxylum Alkylamides Swaps the Tingling with a Numbing Sensation and Diminishes Salivation

The methanol soluble prepared from a supercritical fluid extract of Szechuan pepper (Zanthoxylum piperitum) was screened for its key tingling and numbing chemosensates by application of taste dilution analysis. Further separation of fractions perceived with the highest sensory impact, followed by LC-TOF-MS, LC-MS, and 1D/2D NMR experiments, led to the structure determination of the known alkylamides hydroxy-γ-sanshool (1), hydroxy-α-sanshool (2), hydroxy-β-sanshool (3), bungeanool (4), isobungeanool (5), and hydroxy-γ-isosanshool (6), as well as hydroxy-ε-sanshool (7), the structure of which has not yet been confirmed by NMR, and hydroxy-ζ-sanshool (8), which has not been previously reported in the literature. Psychophysical half-tongue experiments using filter paper rectangles (1 × 2 cm) as the vehicle revealed amides 1, 2, 4, 5, 7, and 8, showing at least one cis-configured double bond, elicited the well-known tingling and paresthetic orosensation above threshold levels of 3.5-8.3 nmol/cm(2). In contrast, the all-trans-configured amides 3 and 6 induced a numbing and anesthetic sensation above thresholds of 3.9 and 7.1 nmol/cm(2), respectively. Interestingly, the mono-cis-configured major amide 2 was found to induce massive salivation, whereas the all-trans-configuration of 3 did not.

Structural and Sensory Characterization of Key Pungent and Tingling Compounds from Black Pepper (Piper nigrum L.)

To gain a more comprehensive knowledge on whether, besides the well-known piperine, other compounds are responsible for the pungent and tingling oral impression imparted by black pepper, an ethanol extract prepared from black pepper (Piper nigrum L.) was screened for its key sensory-active nonvolatiles by application of taste dilution analysis (TDA). Purification of the compounds perceived with the highest sensory impact, followed by LC-MS and 1D/2D NMR experiments as well as synthesis, led to the structure determination of 25 key pungent and tingling phytochemicals, among which the eight amides 1-(octadeca-2E,4E,13Z-trienyl)piperidine, 1-(octadeca-2E,4E,13Z-trienyl)pyrrolidine, (2E,4E,13Z)-N-isobutyl-octadeca-2,4,13-trienamide, 1-(octadeca-2E,4E,12Z-trienoyl)-pyrrolidine, 1-(eicosa-2E,4E,15Z-trienyl)piperidine, 1-(eicosa-2E,4E,15Z-trienyl)pyrrolidine, (2E,4E,15Z)-N-isobutyl-eicosa-2,4,15-trienamide, and 1-(eicosa-2E,4E,14Z-trienoyl)-pyrrolidine were not yet reported in literature. Sensory studies by means of a modified half-tongue test revealed recognition thresholds ranging from 3.0 to 1150.2 nmol/cm² for pungency and from 520.6 to 2162.1 nmol/cm² for the tingling orosensation depending on their chemical structure.

Systematic studies of structure and physiological activity of alapyridaine. A novel food‐born taste enhancer

By application of taste dilution analysis (+)-(S)-1-(1-carboxyethyl)-5-hydroxy-2-(hydroxymethyl)-pyridinium inner salt was recently successfully identified as a multimodal taste enhancer in beef bouillon. While being taste-less on its own, this so-called alapyridaine was found to intensify the human perception of sweet, salty, and umami taste. To gain information on the molecular requirements of this novel class of taste enhancer, a range of structurally related pyridinium betaines were synthesized, purified, and their physiological activities sensorially evaluated. Removal or modification of the hydroxyl and the hydroxymethyl group, respectively, induced a loss in bioactivity, thus indicating the 2-(hydroxymethyl)-5-hydroxypyridinium moiety as an essential structural element for taste enhancement. Regarding the amino substituent, neither the prolongation or removal of the alkyl chain or the carboxy function in the 1-(1-carboxy-2-ethyl)-moiety, nor the incorporation of an additional carboxy function led to any active derivative, thus demonstrating that also the structure of the nitrogen substituent is rather conserved for taste enhancement. But substitution of the methyl group by a benzyl group yielded a compound showing similar taste enhancing activities as found for alapyridaine. Interestingly, additional insertion of glycine between the 1-(1-carboxy-2-phenylethyl)-moiety and the pyridinium ring resulted in a compound eliciting comparable taste enhancing effects as shown for the compound lacking the glycine spacer. In contrast to these multimodal taste enhancers, substitution of the alanine moiety in alapyridaine by an arginine moiety revealed an one-dimensional taste enhancer exclusively increasing the human sensitivity for salty taste.

Reinvestigation of the chemical structure of bitter-tasting quinizolate and homoquinizolate and studies on their Maillard-type formation pathways using suitable (13)C-labeling experiments.

Very recently, application of taste dilution analysis to heated xylose/alanine solutions led to the isolation of two bitter-tasting compounds exhibiting extraordinarily low detection thresholds of 0.00025 and 0.001 mmol/kg of water, respectively. On the basis of LC-MS and NMR spectroscopy, the structures of these compounds, named quinizolate and homoquinizolate, were proposed as 1-oxo-1H,4H-quinolizinium-7-olates. Since recent experiments in our laboratory shed some doubt on the entire correctness of their structures, labeling experiments with mixtures of multiply (13)C-labeled and nonlabeled pentoses were performed to follow the joint transfer of several (13)C atoms en bloc into the bitter compounds by LC-MS and NMR isotopomer diagnosis. The site-specific visualization of the mosaics assembled from (13)C-labeled and (12)C-labeled carbon modules in both bitter compounds demonstrated the structures of quinizolate and homoquinizolate to be the previously unknown (2E)-7-(2-furylmethyl)-2-(2-furylmethylidene)-3-(hydroxymethyl)- and (2E)-7-(2-furylmethyl)-2-(2-furylmethylidene)-3,8-bis(hydroxymethyl)-1-oxo-2,3-dihydro-1H-indolizinium-6-olate.

Characterization of Natural “Cooling” Compounds Formed from Glucose and l-Proline in Dark Malt by Application of Taste Dilution Analysis

Gel permeation chromatography of the solvent extractables isolated from a thermally treated glucose/L-proline mixture and sensory analysis of the fractions collected led to the discovery of the presence of "cooling" compounds in Maillard reactions. To characterize the key compounds imparting this cooling sensation to the oral cavity, a taste dilution analysis was performed by determining the taste threshold of reaction products in serial dilutions of HPLC fractions to select the most intense "cooling" compounds in the complex GPC fraction of the Maillard reaction mixture. Systematic (13)C-labeling experiments and GC-MS, LC-MS, and 1D- and 2D-NMR measurements, followed by synthesis, led to the unequivocal identification of 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC), 5-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-MPC), and 2,5-dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone (DMPF) as the key compounds contributing the most to the cooling sensation. Although these structures were described earlier with regard to Maillard reactions, this is the first time that Maillard reaction products are reported to cause intense cooling sensations by degustation. Finally, the detection of 5-MPC (101.3 microg/kg), 3-MPC (9.4 microg/kg), and DMPF (11.5 microg/kg) in dark malt verified their natural occurrence in thermally processed foods.

Characterization of an intense bitter-tasting 1H,4H-quinolizinium-7-olate by application of the taste dilution analysis, a novel bioassay for the screening and identification of taste-active compounds in foods.

Thermal treatment of aqueous solutions of xylose and primary amino acids led to rapid development of a bitter taste of the reaction mixture. To characterize the key compound causing this bitter taste, a novel bioassay, which is based on the determination of the taste threshold of reaction products in serial dilutions of HPLC fractions, was developed to select the most intense taste compounds in the complex mixture of Maillard reaction products. By application of this so-called taste dilution analysis (TDA) 21 fractions were obtained, among which 1 fraction was evaluated with by far the highest taste impact. Carefully planned LC-MS as well as 1D and 2D NMR experiments were, therefore, focused on the compound contributing the most to the intense bitter taste of the Maillard mixture and led to its unequivocal identification as the previously unknown 3-(2-furyl)-8-[(2-furyl)methyl]-4-hydroxymethyl-1-oxo-1H,4H-quinolizinium-7-olate. This novel compound, which we name quinizolate, exhibited an intense bitter taste at an extraordinarily low detection threshold of 0.00025 mmol/kg of water. As this novel taste compound was found to have 2000- and 28-fold lower threshold concentrations than the standard bitter compounds caffeine and quinine hydrochloride, respectively, quinizolate might be one of the most intense bitter compounds reported so far.