Key Taste Compounds Research Articles

The effect of different drying temperatures on flavonoid glycosides in white tea: A targeted metabolomics, molecular docking, and simulated reaction study

Drying is an important stage used to improve the quality of white tea (WT). However, the effect of the drying temperature on the key taste compounds in WT remains unclear. In this study, targeted metabolomics, molecular docking, and a simulated reaction were used to investigate the transformation mechanism of flavonoid glycosides (FGs) in WT during drying at 60, 80, and 100 °C and its impact on taste. There were 45 differential FGs in WT at three drying temperatures. Compared with the withering samples for 48 h, the total FGs contents at three drying temperatures showed a decreasing trend, with quercetin-3-O-galactoside and kaempferol-3-O-glucoside showing the most degradation. These results were confirmed via a simulated drying reaction of FGs standards. Drying at 80 and 100 °C contributed to the formation of flavonoid-C-glycosides, but only trace amounts of these compounds were observed. In addition, nine key taste FGs were selected using dose-over-threshold values. These FGs regulated the taste of WT, mainly by binding to taste receptors via hydrogen bond, hydrophobic and electrostatic interactions. Finally, the taste acceptability of WT dried at 60 °C was found to be the highest, as this method could properly reduce the contents of FGs, weaken the bitterness and astringency, and retain the sweet and umami taste. This study revealed for the first time the transformation mechanism of sensory-active FGs affected by drying temperature, which provides a novel perspective for the analysis of the formation mechanism of the unique flavor of WT and the optimization of this process.

Umami taste perception and preferences of the domestic cat (Felis catus), an obligate carnivore.

The domestic cat (Felis catus) is an obligate carnivore, and as such has a meat-based diet. Several studies on the taste perception of cats have been reported, indicating that their sense of taste has evolved based on their carnivorous diet. Here we propose that umami (mediated by Tas1r1-Tas1r3) is the main appetitive taste modality for the domestic cat by characterising the umami taste of a range of nucleotides, amino acids and their mixtures for cats obtained using complementary methods. We show for the first time that cats express Tas1r1 in taste papillae. The cat umami receptor responds to a range of nucleotides as agonists, with the purine nucleotides having the highest activity. Their umami receptor does not respond to any amino acids alone, however, 11 L-amino acids with a range of chemical characteristics act as enhancers in combination with a nucleotide. L-Glutamic acid and L-Aspartic acid are not active as either agonists or enhancers of the cat umami receptor due to changes in key binding residues at positions 170 and 302. Overall, cats have an appetitive behavioural response for nucleotides, L-amino acids, and their mixtures. We postulate that the renowned palatability of tuna for cats may be due, at least in part, to its specific combination of high levels of inosine monophosphate and free L-Histidine that produces a strong synergistic umami taste enhancement. These results demonstrate the critical role that the umami receptor plays in enabling cats to detect key taste compounds present in meat.

Quantitative studies, taste recombination, and omission experiments on the key taste compounds in Chinese and Japanese soy sauce

The non-volatile compounds in Chinese soy sauce (CSS) and Japanese soy sauce (JSS) were qualitatively and quantitatively identified by amino acid analyser and gas-chromatography mass-spectrometry combined with derivatization method (DER-GC–MS). Forty-nine compounds were identified, including 19 amino acids, 8 sugars, 6 sugar alcohols, 8 organic acids and 8 others. Six groups of taste compounds were added to the water at natural concentration in soy sauce were able to reconstitute taste models of CSS and JSS, with no remarkable differences from the soy sauce taste profiles. Through three different rounds of omission tests, it was clear that the recombination models of 10 and 11 key compounds could simulate the typical taste characteristics of CSS and JSS, respectively, with the shared compounds NaCl, glutamate, lysine, isoleucine, leucine, lactic acid, citric acid, and > 500 Da components. This study provided an important theoretical basis for the in-depth research on the soy sauce flavor.

Characterization of the key nonvolatile metabolites in Cheddar cheese by partial least squares regression (PLSR), reconstitution, and omission

Cheddar cheese was desirable by consumers worldwide due to its characteristic taste and aroma, but limited information was available about taste contributors. Therefore, sensory profiles of natural Cheddar cheeses were investigated by quantitative descriptive analysis (QDA). Umami, salty, and brothy attributes were the principal differential attributes. Nonvolatile metabolites were analyzed to decipher their taste contributions, of which free amino acids (FAAs) and organic acids recorded the most considerable differences. The key taste compounds were identified by partial least squares regression (PLSR), reconstitution, and omission tests. NaCl and glutamic acid (Glu) were the primary contributors of salty and umami tastes, respectively. Sourness was synergistically affected by organic acids and Glu. Despite their limited taste impacts, the remaining amino acids intensified sourness and saltiness when mixed with Glu. Organic acids (especially in combination) and NaCl exhibited significant taste enhancements. These results provided deep insight into crucial nonvolatile metabolites promoting Cheddar cheese tastes.

Characterization of Taste Compounds and Sensory Evaluation of Soup Cooked with Sheep Tail Fat and Prickly Ash.

Sheep tail fat and prickly ash play an important role in improving the umami taste of mutton soup. In this work, the effects of prickly ash on key taste compounds in stewed sheep tail fat soup were investigated. Results showed that the taste intensity of sheep tail fat soup cooked with 0.2% prickly ash increased significantly. The concentration of organic acids and free amino acids in sheep tail fat soup significantly increased with the addition of prickly ash. The concentration of succinic acid (2.637 to 4.580 mg/g) and Thr (2.558 to 12.466 mg/g) increased the most among organic acids and amino acids, respectively. Spearman’s correlation analysis elucidated that seven taste compounds were positively correlated (correlation coefficient > 0.7) with the overall taste intensity of the soup sample including Thr, Asp, oxalic acid, lactic acid, citric acid, succinic acid, and ascorbic acid. Additional experiments and quantitative descriptive analysis further confirmed that Asp, lactic acid and citric acid were the key taste compounds to improve saltiness and umami taste in sheep tail fat soup with prickly ash.

EVALUATION OF NON-VOLATILE KEY TASTE COMPOUNDS OF AIR-DRIED HERRING (Clupea pallasii) FILLET

An experiment was conducted to quantify the non-volatile key taste compounds, including free amino acids (FAAs), nucleotides, inorganic ions, organic acids, and bases of dried herring (Clupea pallassi) fillet (DHF). A taste recombinant was also prepared using those key taste compounds to compare the taste profiles with water soluble extracts (WSE) by sensory perception. The total FAA of DHF muscle was 12.25 mg/g on dry matter basis. The most dominant FAAs were alanine, glycine, lysine, and histidine. The nucleotides were identified as 5´-adenosine monophosphate (AMP) (1.74 mg/100 g) and 5´-inosine monophosphate (IMP) (5.28 mg/100 g). Potassium, phosphate, and chloride were the major inorganic ions while trimethylamine oxide, creatine, and lactic acid were the major organic bases. Sensory evaluation showed that WSE markedly increased the intensities of umami, mouthfulness, thickness, and taste continuity of Japanese noodle soup (JNS). However, addition of taste recombinant to the JNS did not bring any changes in the taste intensities of saltiness, umami, mouthfulness, taste continuity, and thickness of the soup. Results of this study indicated that the taste recombinant was lacking of some important key taste compounds that might be formed during drying of herring fillet.

Characterization of the key taste compounds during bread oral processing by instrumental analysis and dynamic sensory evaluation

The process of taste release and perception during chewing bread was investigated using high-performance liquid chromatography and sodium ion-selective electrode analysis combined with dynamic sensory evaluation. The result of the dynamic quantitative descriptive analysis and temporal dominance of sensation elucidated that sour, salty, and sweet tastes were significantly (P < 0.05) changed during oral processing. The salty taste was the dominant taste at the initial stage of chewing, whereas the sweet taste took the dominant place after 7 s. Seventeen taste-active compounds with the taste activity value more than 1 were identified. According to partial least squares regression analysis, 9 taste compounds were detected as the potent taste compounds contributing to changes in the taste perception during bread oral processing. Malic acid, succinic acid, sodium chloride, valine, and sucrose were confirmed as the key taste compounds contributing to bread oral processing through addition experiments. Malic acid had a stronger enhancing ability of sour and salty perception than succinic acid but weaker inhibition ability to decrease sweet perception than succinic acid.

Comparison of nonvolatile and volatile compounds in raw, cooked, and canned yellowfin tuna ( Thunnus albacores )

Yellowfin tuna is one of the favorite aquatic foods and possesses high economic value due to its unique pleasant flavor and good nutrition quality. Volatile and nonvolatile compounds that affect the flavor quality of tuna fish during canning process were investigated. The volatiles were analyzed by headspace solid‐phase microextraction combined with GC‐MS and the nonvolatiles were characterized by free amino acids, 5′‐nucleotides, and organic acids. Histidine, lysine, inosinic acid, tartaric acid, and succinic acid were the key taste compounds in tuna fish. A total of 7, 9, and 7 aroma‐active compounds were identified in raw, cooked, and canned fish samples, respectively. Decanal, nonanal, octanal, and (E)‐2‐nonenal were the predominant odorants in raw samples. Octanal, nonanal, 2‐pentylfuran, 1‐octen‐3‐ol, hexanal, and 2‐ethylfuran contributed to the characteristic flavor of cooked samples. 2‐Methyl‐3‐furanthiol, octanal, and nonanal were the main aroma‐active compounds detected in the canned samples responsible for the meaty and fatty odor. PRACTICAL APPLICATIONS: Yellowfin tuna is one of the most commercial fish species for its excellent economic and nutritional value. The tuna fish processing methods are mainly frozen, cooked, smoked, and canned after thermal processing. The flavor components of tuna would vary greatly depending on the processing method. Although quality characteristics are very important for the economic value of tuna, there is scarce information comparing the volatile and nonvolatile compounds in tuna meat during canning process. This research could provide basis data for the process and the quality improvement of tuna products.

Application of metabolomics profiling in the analysis of metabolites and taste quality in different subtypes of white tea

Three subtypes of white tea, Silver Needle (SN), White Peony (WP), and Shou Mei (SM), differ in their taste, aroma, bioactivity, and commercial value. Here, a metabolomics investigation on the chemical compositions combining taste equivalent-quantification and dose-over-threshold (DoT) determination on the taste qualities were applied to comprehensively characterize the white tea subtypes for the first time. Significant differences in the contents of catechins, dimeric catechins, amino acids, phenolic acids, flavonol/flavone glycosides, and aroma precursors were observed among these 3 white teas. Metabolite content comparison and partial least-squares (PLS) analysis suggest that theanine, aspartic acid, asparagine, and AMP were positively correlated with the umami taste in white tea, and flavan-3-ols, theasinensins, procyanidin B3, and theobromine had positive correlations with higher bitterness and astringency tastes. In addition, puckering astringent (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG) and theogallin, bitter-tasting caffeine, and the mouth-drying/velvety-like astringent γ-aminobutyric acid (GABA) were identified as key taste compounds of white tea infusion by absolute quantification and DoT factor calculations. This work provided systematic and comprehensive knowledge on the chemical components, taste qualities, and sensory active metabolites for the subtypes of white tea.

Compositional and sensory characterization of grape proanthocyanidins and oak wood ellagitannin

Aimed at increasing our knowledge on the astringency of sensory-active non-volatile compounds migrating principally from grapes and from oak wood into the wine, grape extracts and an aqueous ethanolic extract from oak wood chips were used for their key taste compounds. Monomeric/oligomeric and polymeric proanthocyanidin fraction of seed and skin extracts were obtained from grapes. Ellagitannins were extracted and purified from oak wood. Compositional characterization, purity and sensory evaluation of grape extracts were performed by liquid chromatography/mass spectrometry and sensory analysis, respectively. Purification of ellagitannin extract at 93.4% was realized by successive fractionations on Toyopearl TSK HW-40 (F) and on C-18 column. At the same concentration, ellagitannin fraction was perceived rather mellow, seed and skin monomeric/oligomeric fraction was characterized slight astringent, polymeric seed fraction was identified as tannic whereas polymeric skin fraction was appreciated rather mellow.

Molecular Definition of the Taste of Roasted Cocoa Nibs (Theobroma cacao) by Means of Quantitative Studies and Sensory Experiments

Sensory-guided decomposition of roasted cocoa nibs revealed that, besides theobromine and caffeine, a series of bitter-tasting 2,5-diketopiperazines and flavan-3-ols were the key inducers of the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a number of polyphenol glycopyranosides as well as a series of N-phenylpropenoyl-l-amino acids have been identified as key astringent compounds of roasted cocoa. In the present investigation, a total of 84 putative taste compounds were quantified in roasted cocoa beans and then rated for the taste contribution on the basis of dose-over-threshold (DoT) factors to bridge the gap between pure structural chemistry and human taste perception. To verify these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of the individual taste compounds in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail was very close to the taste profile of an aqueous suspension of roasted cocoa nibs. To further narrow down the number of key taste compounds, finally, taste omission experiments and human dose/response functions were performed, demonstrating that the bitter-tasting alkaloids theobromine and caffeine, seven bitter-tasting diketopiperazines, seven bitter- and astringent-tasting flavan-3-ols, six puckering astringent N-phenylpropenoyl-l-amino acids, four velvety astringent flavonol glycosides, gamma-aminobutyric acid, beta-aminoisobutyric acid, and six organic acids are the key organoleptics of the roasted cocoa nibs.

Sensory-Directed Identification of Taste-Active Ellagitannins in American (Quercus albaL.) and European Oak Wood (Quercus roburL.) and Quantitative Analysis in Bourbon Whiskey and Oak-Matured Red Wines

Aimed at increasing our knowledge on the sensory-active nonvolatiles migrating from oak wood into alcoholic beverages upon cooperaging, an aqueous ethanolic extract prepared from oak wood chips (Quercus alba L.) was screened for its key taste compounds by application of the taste dilution analysis. Purification of the compounds perceived with the highest sensory impacts, followed by liquid chromatography/mass spectrometry as well as one-dimensional and two-dimensional NMR experiments, revealed the ellagitannins vescalagin, castalagin, and grandinin, the roburins A-E, and 33-deoxy-33-carboxyvescalagin as the key molecules imparting an astringent oral sensation. To the best of our knowledge, 33-deoxy-33-carboxyvescalagin has as yet not been reported as a phytochemical in Q. alba L. In addition, the sensory activity of these ellagitannins was determined for the first time on the basis of their human threshold concentrations and dose/response functions. Furthermore, the ellagitannins have been quantitatively determined in extracts prepared from Q. alba L. and Quercus robur L., respectively, as well as in bourbon whiskey and oak-matured red wines, and the sensory contribution of the individual compounds has been evaluated for the first time on the basis of dose/activity considerations.

Quantitative Studies, Taste Reconstitution, and Omission Experiments on the Key Taste Compounds in Morel Mushrooms (Morchella deliciosa Fr.)

Sensory-directed fractionation of an aqueous extract prepared from morel mushrooms led to the identification of gamma-aminobutyric acid as the chemical inducer of the mouth-drying and mouth-coating oral sensation imparted by morels. Additionally, L-glutamic acid, L-aspartic acid, succinic acid, and the previously unknown (S)-malic acid 1-O-beta-D-glucopyranoside, coined (S)-morelid, were detected as additional important umami-like taste compounds. To further bridge the gap between pure structural chemistry and human taste perception, 33 putative taste compounds were quantified in an aqueous morel extract and then rated for their taste contribution on the basis of dose-over-threshold factors. To confirm these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of 16 amino acids, 6 organic acids, 3 purines, 4 carbohydrates, 3 minerals, and (S)-morelid in their "natural" concentrations. Triangle tests revealed that the taste profile of this biomimetic organoleptic cocktail did not differ significantly from the taste profile of authentic morel extract. To finally narrow down the number of key taste compounds, taste omission experiments were performed demonstrating that (S)-morelid together with L-glutamic acid, L-aspartic acid, malic acid, citric acid, acetic acid, and gamma-aminobutyric acid are the key organoleptics of morel extract. Moreover, sensory experiments with model solutions showed that (S)-morelid not only imparts a sour and umami-like taste but is able to amplify the taste activity of monosodium glutamate, as well as sodium chloride, solutions.

Molecular Definition of Black Tea Taste by Means of Quantitative Studies, Taste Reconstitution, and Omission Experiments

Recently, bioresponse-guided fractionation of black tea infusions indicated that neither the high molecular weight thearubigens nor the theaflavins, but a series of 14 flavon-3-ol glycopyranosides besides some catechins, might be important contributors to black tea taste. To further bridge the gap between pure structural chemistry and human taste perception, in the present investigation 51 putative taste compounds have been quantified in a black tea infusion, and their dose-over-threshold (Dot) factors have been calculated on the basis of a dose/threshold relationship. To confirm these quantitative results, an aqueous taste model was prepared by blending aqueous solutions of 15 amino acids, 14 flavonol-glycosides, 8 flavan-3-ols, 5 theaflavins, 5 organic acids, 3 sugars, and caffeine in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail did not differ significantly from the taste profile of the authentic tea infusion. To further narrow the number of key taste compounds, finally, taste omission experiments have been performed, on the basis of which a reduced recombinate was prepared containing the bitter-tasting caffeine, nine velvety astringent flavonol-3-glycosides, and the puckering astringent catechin as well as the astringent and bitter epigallocatechin-3-gallate. The taste profile of this reduced recombinate differed not significantly from that of the complete taste recombinate, thus confirming these 12 compounds as the key taste compounds of the tea infusion. Additional sensory studies demonstrated for the first time that the flavanol-3-glycosides not only impart a velvety astringent taste sensation to the oral cavity but also contribute to the bitter taste of tea infusions by amplifying the bitterness of caffeine.

Isolation, Structure Determination, Synthesis, and Sensory Activity of N-Phenylpropenoyl-l-amino Acids from Cocoa (Theobroma cacao)

Application of chromatographic separation and taste dilution analyses recently revealed besides procyanidins a series of N-phenylpropenoyl amino acids as the key contributors to the astringent taste of nonfermented cocoa beans as well as roasted cocoa nibs. Because these amides have as yet not been reported as key taste compounds, this paper presents the isolation, structure determination, and sensory activity of these amino acid amides. Besides the previously reported (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine (clovamide), (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-tyrosine (deoxyclovamide), and (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-tyrosine, seven additional amides, namely, (+)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-aspartic acid, (+)-N-[4'-hydroxy-(E)-cinnamoyl]-L-aspartic acid, (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-glutamic acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-glutamic acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine, (+)-N-[4'-hydroxy-3'-methoxy-(E)-cinnamoyl]-L-aspartic acid, and (+)-N-[(E)-cinnamoyl]-L-aspartic acid, were identified for the first time in cocoa products by means of LC-MS/MS, 1D/2D-NMR, UV-vis, CD spectroscopy, and polarimetry, as well as independent enantiopure synthesis. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying oral sensation were determined to be between 26 and 220 micromol/L (water) depending on the amino acid moiety. In addition, exposure to light rapidly converted these [E]-configured N-phenylpropenoyl amino acids into the corresponding [Z]-isomers, thus indicating that analysis of these compounds in food and plant materials needs to be performed very carefully in the absence of light to prevent artifact formation.