Bitter Sensations Research Articles

CORRELATION OF OLEOCANTHAL AND OLEACEIN CONCENTRATION WITH PUNGENCY AND BITTERNESS IN 'KORONEIKI' VIRGIN OLIVE OIL

It is known that the organoleptic attributes of pungency and bitterness in olive oil are attributed to phenolic compounds. Recent research has demonstrated that oleocanthal, a secoiridoic phenolic, is a naturally occurring anti-inflammatory and neuroprotective agent, and that it elicits a throat stinging sensation through a specific TRPA1 receptor. Oleacein, a hydroxytyrosol derivative is considered as the most powerful antioxidant in olive oil and although it differs from oleocanthal only by one additional phenolic hydroxyl, organoleptically it is associated more with bitterness and less with pungency. The present study examined the correlations between oleocanthal and oleacein concentrations and the intensity of pungent and bitter sensations in a group of 21 virgin olive oil samples of the ‘Koroneiki’ cultivar, produced in a specific geographic region of Greece (Messini). The qualitative and quantitative determination of the chemical compounds was carried out by a new method based on quantitative 1H-NMR in CDCl3 at 600 MHz after extraction of olive oil with acetonitrile. The concentrations of the studied compounds ranged for oleocanthal between 34.6-154.6 mg/L (mean value 94.5±31.8 mg/L) and for oleacein between 11.5-191.9 mg/L (mean value 63.3±36.1 mg/L). The organoleptic assessment of the samples was performed by a trained sensory panel according to the IOC method. The values of the positive attributes were distributed between 0.40-2.65 (mean value 1.45±0.72) for bitterness, 1.50-3.70 (mean value 2.62±0.56) for pungency and 0.40-3.60 (mean value 2.14±0.82) for fruitiness. The results showed that there is a positive correlation (r=0.79, p≤0.05) between the concentration of oleocanthal and oleacein, and the intensity of pungency and bitterness, suggesting that virgin olive oils with intense organoleptic attributes may offer more health benefits. Moreover, a proposal for a new index for describing and quantifying the positive organoleptic attributes of virgin olive oils is discussed.

Disgeusia: a propósito de um caso clínico

Introduction: The distortion of the sense of taste (dysgeusia), transient or permanent, may have significant impact on the lives of patients. It may be associated with weight loss, anorexia, malnutrition, depressive symptoms, and a significant reduction in quality of life. Dysgeusia can have several causes. One surgical cause is tonsillectomy. Case description: A 38 year-old female patient, with dysgeusia is presented. She had a history of bilateral chronic tonsillitis and a cold blade tonsillectomy was performed with electrocautery of tonsillar hemorrhages without complications. After surgery she complained of dysgeusia characterized by lack of taste discrimination, stating that all foods seemed bitter. Six months after surgery, at a follow-up consultation, her gustatory function was evaluated with taste strips. This revealed changes in taste discrimination. She experienced a bitter taste, even when stimulated with sour, sweet or salty stimuli. The patient began daily gustatory rehabilitation, working on mental associations with sensory stimuli. She repeated the gustometry one year after surgery. The patient improved, although selective dysgeusia persisted with a bitter sensation in the presence of salt at low concentration. Comment: Dysgeusia is a rare complication of tonsillectomy, but can have great impact on the lives of patients. The surgical procedure can damage sensory nerves responsible for taste, directly or indirectly. There are few therapeutic options. Cases are under reported in the literature, and tend to be benign. Dysgeusia can have various causes, such as antihypertensive drugs, poor oral hygiene, surgery, infection, smoking, diabetes, autoimmune diseases, anti-microbial agents, and anti-inflammatory drugs. In primary health care, taste complaints often have no obvious explanation at the initial presentation. In Portugal there is no data on their incidence. It is important to sensitize clinicians to this disease. Patients’ complaints about changes in taste should be addressed because of the impact that it has on the quality of life and possible treatable causes. Patients with dysgeusia require assessment, advice and treatment.

Proanthocyanidin composition and evolution during grape ripening as affected by variety: Nebbiolo and Barbera cv.

<p class="Sansinterligne1" style="text-align: justify;"><strong>Aim</strong>: Proanthocyanidin (PA) content, composition and evolution during berry development was determined in two cv., Nebbiolo and Barbera, quite different in their polyphenolic profile.</p><p class="Standard" style="text-align: justify;"><strong>Methods and results</strong>: PAs were extracted separately from seeds and skins, before véraison until maturity. Intact extracts were fractionated according to PA degree of polymerization. Nebbiolo grapes presented a significantly higher PA content in both seeds and skins. PA depolymerization reactions as well as a weaker decrease in polymeric PAs occurred in Barbera skins. Oligomeric PAs prevailed over polymeric ones in Barbera seeds. At harvest, Nebbiolo skins presented a significantly higher percentage of oligomeric PAs, while monomeric and oligomeric flavanol percentages were significantly higher in Barbera seeds.</p><p class="Standard" style="text-align: justify;"><strong>Conclusion</strong>: Barbera and Nebbiolo grapes differ also in their PA total amount and structure. PA content in grape skins and seeds, their distribution in monomeric, oligomeric and polymeric fractions, as well as their decrease rate during fruit ripening are different between the cv.</p><strong>Significance and impact</strong> <strong>of the study</strong>: The fractionation results, obtained for Nebbiolo and Barbera grapes for the first time, highlight how grape variety affects the PA profile. Furthermore, this study is the basis for better understanding the astringency and bitter sensation in Barbera and Nebbiolo grapes and wines.

Diet Shapes the Evolution of the Vertebrate Bitter Taste Receptor Gene Repertoire

Vertebrate Tas2r taste receptors bind to bitter compounds, which are typically poisonous, to elicit bitter sensation to prevent the ingestion of toxins. Previous studies noted a marked variation in the number of Tas2r genes among species, but the underlying cause is unclear. To address this question, we compile the Tas2r gene repertoires from 41 mammals, 4 birds, 2 reptiles, 1 amphibian, and 6 fishes. The number of intact Tas2r genes varies from 0 in the bottlenose dolphin to 51 in the Western clawed frog, with numerous expansions and contractions of the gene family throughout vertebrates, especially among tetrapods. The Tas2r gene number in a species correlates with the fraction of plants in its diet. Because plant tissues contain more toxic compounds than animal tissues do, our observation supports the hypothesis that dietary toxins are a major selective force shaping the diversity of the Tas2r repertoire.

Association of a bitter taste receptor mutation with Balkan Endemic Nephropathy (BEN)

BackgroundBalkan Endemic Nephropathy (BEN) is late-onset kidney disease thought to arise from chronic exposure to aristolochic acid, a phytotoxin that contaminates wheat supplies in rural areas of Eastern Europe. It has recently been demonstrated that humans are capable of perceiving aristolochic acid at concentrations below 40 nM as the result of high-affinity interactions with the TAS2R43 bitter taste receptor. Further, TAS2R43 harbors high-frequency loss-of-function mutations resulting in 50-fold variability in perception. This suggests that genetic variation in TAS2R43 might affect susceptibility to BEN, with individuals carrying functional forms of the receptor being protected by an ability to detect tainted foods.MethodsTo determine whether genetic variation in TAS2R43 predicts BEN susceptibility, we examined genotype-phenotype associations in a case–control study. A cohort of 88 affected and 99 control subjects from western Bulgaria were genotyped with respect to two key missense variants and a polymorphic whole-gene deletion of TAS2R43 (W35S, H212R, and wt/Δ), which are known to affect taste sensitivity to aristolochic acid. Tests for association between haplotypes and BEN status were then performed.ResultsThree major TAS2R43 haplotypes observed in previous studies (TAS2R43-W35/H212, -S35/R212 and –Δ) were present at high frequencies (0.17, 0.36, and 0.47 respectively) in our sample, and a significant association between genotype and BEN status was present (P = 0.020; odds ratio 1.18). However, contrary to expectation, BEN was positively associated with TAS2R43-W35/H212, a highly responsive allele previously shown to confer elevated bitter sensitivity to aristolochic acid, which should drive aversion but might also affect absorption, altering toxin activation.ConclusionsOur findings are at strong odds with the prediction that carriers of functional alleles of TAS2R43 are protected from BEN by an ability to detect and avoid aristolochic acid exposure. Evidence for a positive association between high-sensitivity alleles and BEN status suggests instead that possession of toxin-responsive receptor variants may paradoxically increase vulnerability, possibly by shifting attractive responses associated with low-intensity bitter sensations. The broad-spectrum tuning of the ~25-member TAS2R family as a whole toward xenobiotics points to a potentially far-reaching relevance of bitter responses to exposure-related disease in both individuals and populations.

Identification of TRPM5 Ion Channels in Type-II Taste Cells of Mice

TRPM5 are ion channels belonging to the TRP family, which demonstrate a nonselective permeability for monovalent cations and are activated by an increase in the intracellular calcium level. TRPM5 are present in taste receptor cells of type II responsible for reception of bitter, sweet, and umami taste sensations. Knockout of the trpm5 gene in mice results in a nearly complete loss of sensitivity to taste stimuli of the above-mentioned modalities (taste blindness). The physiological activity of TRPM5 in taste receptive cells has practically not been studied. Using a patch-clamp technique, we carried out a comparative analysis of the properties of recombinant TRPM5 and Ca2+-activated membrane channels in type-II taste cells in mice. Dialysis of the studied cells with a high-Ca2+ solution and application of a calcium ionophore, ionomycin, caused activation of outward-rectification ion channels permeable for Na+, Cs+, and K+ in CHO-strain cells with exogenous TRPM5. These channels were blocked by 100 μM triphenylphosphine oxide (TPPO). Calcium-activated channels in type-II taste cells also possessed analogous properties. Application of the calcium ionophore ionomycin or a stepwise increase in the intracellular Ca2+ level using photolysis (uncaging) caused activation of channels nonselective with respect to Na+ and Cs+ and impermeable for N-methyl-D-glucamine (NMDG+). These channels had the current–voltage characteristics of outward rectification and a high thermosensitivity (Q10 = 6.7 ± 0.5); they could be blocked by TPPO. It should be emphasized that TRPM5 were specific with respect to type-II cells. An increase in the intracellular calcium level induced the appearance of Cl– current in type-I cells and did not influence the basic current in type-III cells.

Bittersweet

ABSTRACTFor Uitoto communities in the borderlands of the Colombian Amazon, ordinary sociality depends on the effective rendering of sweet social relations from a universe of bitterly antisocial possibilities. Human personhood and kinship must be continually materialized through the transformation of bitter substances and sensations into sweet ones, and the incorporation of sweetness as a sensible quality of moral personhood. In a context where the sensorium is frequently transposed into a moral register, taste qualities both index and transmit the moral qualities of persons, and the bittersweet potentialities of kinship relations are mediated through botanical instruments of moral transformation. This paper explores the qualities of dulzura (sweetness) and amargura (bitterness) as key terms of value in the moral economy of Uitoto horticulturalists—experts in the management of bitter manioc (manihot escualenta) and bitter feelings alike.

In reference to capsaicin receptors are colocalized with sweet/bitter receptors in the taste sensing cells of circumvallate papillae

Dear Editors,We read with interest the paper ‘‘Capsaicin receptors arecolocalized with sweet/bitter receptors in the taste sensingcells of circumvallate papillae’’ published by Moon et al.[1]. The authors report a double reaction of T1R2-, T1R3-or T2R6 positive vallate cells with anti-VR1 antibodies ofrat circumvallate papillae. They also found that about 60%of VR1 positive cells in the circumvallatae papillae reac-tive with a-gustducin. The authors concluded that capsaicinmay interact with transducin pathways of sweet and bittersensations.Many researchers described the suppressive effects ofcapsaicin on responses to taste stimuli of sweet, bitter, andumami in humans [2–4]. At lower concentrations, capsai-cin can also elicit bitter [4, 5], and sweet sensations [5].Green and Schullery described bitter sensations whencapsaicin was applied to fungiform, foliate, and circum-vallate papillae of the human tongue [4].In our study, capsaicin was applied to the dorsal anteriortongue in healthy subjects. Beside bitter, sour and saltysensations, capsaicin elicited also sweet sensations [5].The presented study reported evidence of VR1 receptorsin taste cells in circumvallate papillae in rats. Based on theauthor’s findings, one might speculate that VR1 receptorscan also be found in taste cells of the fungiform papillae ofthe dorsal anterior tongue even in humans. This mayexplain why some healthy subjects report sweet sensationsafter stimulation with capsaicin at low concentrations.Knowledge of the VR1 receptors of taste cells of fungiformpapillae may also help to explain symptoms after chordatympani nerve (CTN) transection. In patients with tran-sected CTN the capsaicin thresholds were lower at theipsilateral tongue side compared to the contralateral side[6].We would like to congratulate the authors for theirexcellent study because they clearly emphasize the need forfurther research in taste-trigeminal interactions.References

The use of 2D NMR to study β-cyclodextrin complexation and debittering of amino acids and peptides

Abstract This work fully demonstrated the formation of amino acids complexes with β-cyclodextrin (β-CD) by the method of nuclear magnetic resonance with the rotating frame Overhauser effect spectroscopy (ROESY) and diffusion ordered spectroscopy (DOSY) techniques. The tested amino acids display the following decreasing order of affinity for β-CD: tryptophane > tyrosine > phenylalanine > proline > histidine > isoleucine. The influence of complexation on taste perception was determined with a trained panel to qualify taste alterations of single amino acids and quantify the debittering of soy protein hydrolysate by β-CD complexation. The results showed that β-CD complexation is effective for modifying single amino acids taste perception and debittering soy protein hydrolysate. Bitterness sensation of the latter is reduced by 90% when 5% β-CD was added, thus β-CD is recommended as a prospective additive for masking bitter taste of new functional food products.

Contribution of the Temporal Dominance of Sensations (TDS) method to the sensory description of subtle differences in partially dealcoholized red wines

In this study, effect of partial alcohol reduction on the sensory modification of red wines was investigated. A Merlot and a Syrah wine were partially dealcoholized using reverse osmosis technique to span a range of three different alcohol contents (14–10%) by grape variety. Preliminary triangle tests indicated the existence of very slight differences between the dealcoholized wines of the study. Therefore, adapted descriptive methodologies had to be used. In a first step, wines were described with a comparative sensory profile by 16 trained panellists on 15 sensory attributes. Then, the same panellists profiled the wines with the TDS technique, which consists in identifying and rating sensations perceived as dominant repeatedly until the perception ends. Analysis of variance of the classical descriptive data confirmed the existence of subtle sensory differences among wines from a given grape variety with only three and five discriminated attributes for Merlot and Syrah, respectively. Analysis of TDS curves emphasized twice more discriminated attributes and pointed up temporal differences between wines that did not appear with the conventional sensory profile. Used together these methods appeared as promising as they resulted in complementary and complete descriptions of wines. Effect of dealcoholization was variable from one grape variety to another one. The constant effects of alcohol reduction, common to both Merlot and Syrah were the perception decrease of heat sensation, the substitution of heat sensation in attack by astringent (Merlot) or red fruits (Syrah) sensations, the decrease of bitter sensation after attack to the expense of fruity sensations, and the decrease of length in mouth. In case of Merlot, texture and astringency sensations were also affected by alcohol reduction whereas for Syrah, sweet sensation was affected. Wine is a complex product lying on a fragile balance and the least parameter modification induces variable effects according to the type of wines. Several kinds of interactions between ethanol and wine component must take place and make difficult the generalization of alcohol reduction effect on the sensory perception of wines.

Cucurbitacin C^|^mdash;Bitter Principle in Cucumber Plants

Cucumber plants contain a bitter substance, cucurbitacin C. The compound was isolated from cucumber leaves using preparatory HPLC (high performance liquid chromatography) to investigate the relationship between its content and bitterness of the plant parts. An analytical method for cucurbitacin C using HPLC was also established. A Japanese popular cultivar, 'Sharp 1' contained the compound in the leaves but not in the fruits, while a unique cultivar with white skin 'Shinsyo Hakuhi' contained it both in leaves and fruits. The stem end of 'Shinsyo Hakuhi' fruit contained higher amounts of it than other fruit parts. Cucurbitacin C is a strongly bitter component and its threshold level was less than 0.1 mg/L. The bitter sensation felt when biting the plant parts could be interpreted as corresponding to the content of cucurbitacin C.

BITTER TASTE AND PHENOLIC COMPOUNDS IN EXTRA VIRGIN OLIVE OIL: AN EMPIRICAL RELATIONSHIP

ABSTRACT Bitter taste of extra virgin olive oil is known to be affected by the phenolic composition. However, contribution of each individual phenol to this sensory note has not been clearly defined. The aims of this study were to verify whether there was a relationship between bitter sensation and phenolic compound concentration, to determine which compounds were involved in bitter taste and to evaluate quantitatively this correlation. Results confirmed that a positive correlation did exist between total phenolic amount and bitter intensity. Data processing showed that this correlation was significantly dependent upon a relationship between oleuropein aglycon (3,4‐DHPEA‐EA) and bitter intensity. An empirical exponential model was set up and validated.

SELECTION OF AN ASTRINGENCY REFERENCE STANDARD FOR THE SENSORY EVALUATION OF BLACK TEA

ABSTRACTAstringent and bitter sensations are characteristic sensory qualities of black tea. Three different classes of potential astringent reference standards (two concentrations each of alum and tannic acid and three fruit juices) were evaluated in this study. The perceived astringency, bitterness and sourness of each were profiled using computerized time‐intensity and compared with the astringent intensity of a standardized brew of black tea. The differences in temporal profiles of potential reference standards across taste attributes were evident and intensity ratings were found to be dependent upon the stimulus and its concentration. Both concentrations of tannic acid were evaluated as the highest in perceived bitterness. For the juices, a strong sour taste was perceived in addition to astringency. It was concluded that the best reference standard for the astringency of black tea is a solution of 0.7 g/L alum as it is low in perceived bitterness and sourness.

Taste Discrimination in a Lizard (Anolis carolinensis,Polychrotidae)

The question of whether lizards possess a sense of taste and are able to use it to discriminate between prey items has been debated in the literature for several decades. This study provides evidence that some lizards indeed do use gustation to discriminate between prey items. In laboratory choice experiments, the lizard Anolis carolinensis discriminated between untreated crickets and crickets treated with either dextrose/aspartame powder (produces sweet sensation in humans) or quinine hydrochloride (QHCl) solution or powder (bitter sensation in humans). Although some of the lizards showed a strong preference for crickets treated with dextrose/aspartame powder, all lizards generally avoided prey items treated with QHCl. This avoidance is not affected when access to the vomeronasal organ is blocked. During this study, lizards readily associated taste with color.

Taste receptor cells that discriminate between bitter stimuli.

Recent studies showing that single taste bud cells express multiple bitter taste receptors have reignited a long-standing controversy over whether single gustatory receptor cells respond selectively or broadly to tastants. We examined calcium responses of rat taste receptor cells in situ to a panel of bitter compounds to determine whether individual cells distinguish between bitter stimuli. Most bitter-responsive taste cells were activated by only one out of five compounds tested. In taste cells that responded to multiple stimuli, there were no significant associations between any two stimuli. Bitter sensation does not appear to occur through the activation of a homogeneous population of broadly tuned bitter-sensitive taste cells. Instead, different bitter stimuli may activate different subpopulations of bitter-sensitive taste cells.

Chemosensory transduction mechanisms in taste.

Taste receptor cells transduce sweet, sour, salty, and bitter chemicals into receptor potentials that ultimately result in the perception of taste. The mechanisms involved in this process are only now beginning to be un­ derstood, with the application of modem physiological and biochemical techniques to these relatively small and somewhat inaccessible receptor cells. The information that is emerging from these studies is that taste cells, like other sensory receptors, utilize apically-located ion channels and receptors for sensory transduction. Unlike most other receptor cells, however, taste cells utilize a diversity of mechanisms for sensory transduction. This diversity reflects, in part, the varied molecular structures of compounds comprising the different taste modalities. Sweet-tasting compounds include carbohydrates and some amino acids, compounds generally important in nutrition. Salt taste is produced by monovalent cations; intake of these compounds is important for maintaining electrolyte balance. A large assortment of molecules produce the bitter sensation. These molecules include divalent cations, alkaloids, some amino acids, and denatonium, the most bitter compound known to man. Bitter-tasting compounds are often toxic, and bitter taste is thought to have evolved as a warning signal that a substance should be avoided. Sour taste is mediated by protons and, finally, umami taste is elicited by monosodium

Quantitative structure-activity relationships of the bitter thresholds of amino acids, peptides, and their derivatives.

Bitter thresholds of a total of 93 amino acids, peptides, and their derivatives were analyzed quantitatively by use of hydrophobicity parameters reported for amino acid side chains and those for the whole molecules estimated from partition coefficients obtained experimentally. We also explored the steric parameters that best explained the variation in the intensity of bitterness attributable to the molecular shape. The results showed that the total length along the zigzag peptide backbone chain of the molecule is an important factor. The bitterness of nonzwitterionic N-acyl and ester derivatives and that of neutral N-acyl ester derivatives were expressed by a single, common equation together with those of zwitterionic amino acids and peptides. Thus the interaction via the charge with the receptor site was probably not an indispensible factor for triggering of the bitter sensation. This study, together with earlier ones, may serve as a prototype of approaches toward unraveling structure-activity relationships of complex molecules like amino acids, peptides, and their derivatives that are of medicinal or agricultural importance.

Chemosensory properties of sour tastants

In Experiment 1, a taste quality fractionation procedure was used to establish the degree to which sour and non-sour taste sensations are elicited by six concentrations of each of seven acids: citric, hydrochloric, sulfuric, lactic, malic, phosphoric and tartaric. In general, the acids differed significantly in their ability to elicit sour, salty and bitter sensations, with sulfuric and hydrochloric acids producing the smallest proportions of perceived sourness. Bitterness was found to be the largest non-sour sensation produced, followed by saltiness. The perceived taste qualities of the acids were stable across a wide range of concentrations. In Experiment 2 the extent to which the vapors of these test acids produce detectable intranasal non-gustatory sensations at concentration levels used in many human taste experiments was examined. All acids induced clear intranasal sensations at concentration levels used in some suprathreshold taste paradigms. The results suggest that a number of measures of sour taste sensation may be confounded by non-sour chemosensory factors, including intranasal stimulation.

A peripheral neural correlate of the human fungiform papillae sweet, bitter sensations

A peripheral neural correlate of the human fungiform papillae sweet, bitter sensations

Qualitative identification of the taste of weak sucrose-sodium chloride mixture stimuli

Near-threshold mixtures of sucrose and sodium chloride were shown to elicit acidic or bitter sensations as well as, or instead of, sweetness and saltiness. The probability of a bitter response was relatively stable and consistent with error due to residual noise in the identification task. The acidic response varied in probability with the sodium chloride concentration, and was generally substitutive for a sweet response.