Masking Bitter Taste by Molecules

Modulation of bitter taste receptors by yeast extracts

Yeast extracts (YEs) are used in foods because of their flavour properties and ability to reduce bitterness. The adenosine 5'-monophosphate (AMP) found in YEs is known to decrease the bitterness of some compounds. This study aimed to investigate the ability of YEs to inhibit bitter taste receptors (TAS2Rs) using in vitro cell-based assays. A screen of TAS2Rs activated by AMP and YEs revealed that AMP and the AMP-rich YE activated more TAS2Rs. The inhibitory effect of the AMP-rich YE on seven TAS2Rs activated by bitter agonists was studied. YE reduced TAS2R activation, increased the EC50 value and decreased the maximum amplitude, demonstrating competitive and non-competitive inhibitions. Amongst the nineteen TAS2Rs tested, seven showed 40 % or greater inhibition after treatment of AMP-rich YE. Our data provide a better understanding of the TAS2R inhibition mechanism of AMP-rich YEs and promote their use as a strategy to reduce bitterness in foods and medicines.

The Growing Complexity of Human Bitter Taste Perception

Human bitter perception is important for the identification of potentially harmful substances in food. For quite some years, research focused on the identification of activators for ∼25 human bitter taste receptors. The discovery of antagonists as well as increasing knowledge about agonists of different efficacies has substantially added to the intricacy of bitter taste perception. This article seeks to raise awareness for an underestimated new level of complexity when compound mixtures or even whole food items are assessed for their bitter taste.

Investigating the synergistic effects of high-pressure homogenization and pH shifting on the formation of tryptophan-rich nanoparticles

A combined treatment of high-pressure homogenization (HPH) and pH-shifting on the mixture of α-lactalbumin (α-LA) and tryptophan (Trp) was used to fabricate nanoparticles (α-LA-Trp-NP). The optimal α-LA/Trp ratio (5:1), HPH pressure (206.8 MPa), and recirculation time (40 min) was found to produce small α-LA-Trp-NP (243.0 ± 7.2 nm) with a narrow particle size distribution. Comparing the size and morphology of α-LA-NPs with α-LA-Trp-NPs indicated that the presence of Trp significantly affected the size and morphology of the NPs in the dry form. The stability of the α-LA-Trp-NPs was improved by using the combination of HPH and pH-shifting. The α-LA-Trp-NPs showed better freeze-thaw stability and retained the particle characteristics with heat treatment at 63 °C, 30 min after the freeze-thaw cycle. α-LA-Trp-NPs were also observed to have remarkable stability against pH changes and thermal treatments at 63 °C, 30 min, and 90 °C, 2 min.

Inhibitors of human bitter taste receptors from the five-flavour berry, Schisandra chinensis

The human bitter taste 2 receptor member 16 (TAS2R16) is one of 25 class A G-protein-coupled receptors (GPCRs) and responds to a variety of molecules responsible for the bitter taste sensation perceived in humans. TAS2R16 can be activated by β-glucopyranosides, and its activation can be inhibited by probenecid, a synthetic drug compound used to treat gout. In this study we describe naturally derived compounds which can inhibit the activation of TAS2R16 by salicin in vitro. These compounds belong to the lignan class derived from the fruit of Schisandra chinensis, which is commonly known as the five-flavour berry. We further tested other analogs with this lignan scaffold, found their differential inhibitory activities towards TAS2R16 in vitro, and sought to rationalize the activity using molecular docking of these lignans on a computationally modelled structure of TAS2R16. Selected lignans with inhibitory activity against other TAS2Rs reveal sub-millimolar inhibitory activity towards TAS2R10, TAS2R14, and TAS2R43 in cell-based assays. These compounds with demonstrated in vitro inhibition of bitter taste receptors may serve as tool compounds to investigate the molecular mechanisms of hTAS2Rs biology in gustatory and non-gustatory tissues.

Chemical characterization and quantitative determination of flavonoids and phenolic acids in yerba santa (Eriodictyon spp.) using UHPLC/DAD/Q-ToF

Eriodictyon species, commonly known as yerba santa, are plants native to the Southwestern United States and northern Mexico. The plants are known for their medicinal properties and have been used by indigenous people for centuries to treat various ailments, in particular, respiratory conditions. Despite a long history of traditional use, many of the species have never been fully chemically characterized, and the constituent range of the species has not been comprehensively reported. In an effort to establish a quality control and chemical characterization method, an extensive set of Eriodictyon species samples including E. californicum (n = 85), E. angustifolium (n = 8), E. trichocalyx (n = 5), E. crassifolium (n = 9), E. tomentosum (n = 2), E. traskiae (n = 1), and E. capitatum (n = 1) were investigated. Fourteen compounds comprised of flavonoids and phenolic acids were quantified utilizing an UHPLC/DAD method. The results from the method validation demonstrated excellent linearity (R2 > 0.99) and sensitivity as evidenced by LOD (0.01-0.1 µg/mL) and LOQ (0.05-0.2 µg/mL). Likewise, the method was found to be precise (RSD < 2.78%) with recoveries between 88.9% and 103.2%. Furthermore, by using UHPLC/ESI/Q-ToF data and protonated, deprotonated, and adduct and fragment ions in positive and negative ion modes, we were able to identify 53 compounds in yerba santa plant samples. To the best of our knowledge, this work encapsulates the most comprehensive data set currently available for the chemical characterization and quantification of the primary constituents in Eriodictyon species. Additionally, results of this study also demonstrated the applicability of the developed method for quality assessment of raw material and commercial herbal products containing different Eriodictyon species.

The Impact of Wet Fermentation on Coffee Quality Traits and Volatile Compounds Using Digital Technologies

Fermentation is critical for developing coffee’s physicochemical properties. This study aimed to assess the differences in quality traits between fermented and unfermented coffee with four grinding sizes of coffee powder using multiple digital technologies. A total of N = 2 coffee treatments—(i) dry processing and (ii) wet fermentation—with grinding levels (250, 350, 550, and 750 µm) were analysed using near-infrared spectrometry (NIR), electronic nose (e-nose), and headspace/gas chromatography–mass spectrometry (HS-SPME-GC-MS) coupled with machine learning (ML) modelling. Most overtones detected by NIR were within the ranges of 1700–2000 nm and 2200–2396 nm, while the enhanced peak responses of fermented coffee were lower. The overall voltage of nine e-nose sensors obtained from fermented coffee (250 µm) was significantly higher. There were two ML classification models to classify processing and brewing methods using NIR (Model 1) and e-nose (Model 2) values as inputs that were highly accurate (93.9% and 91.2%, respectively). Highly precise ML regression Model 3 and Model 4 based on the same inputs for NIR (R = 0.96) and e-nose (R = 0.99) were developed, respectively, to assess 14 volatile aromatic compounds obtained by GC-MS. Fermented coffee showed higher 2-methylpyrazine (2.20 ng/mL) and furfuryl acetate (2.36 ng/mL) content, which induces a stronger fruity aroma. This proposed rapid, reliable, and low-cost method was shown to be effective in distinguishing coffee postharvest processing methods and evaluating their volatile compounds, which has the potential to be applied for coffee differentiation and quality assurance and control.

Study on the taste-masking effect and mechanism of Acesulfame K on berberine hydrochloride

OBJECTIVE

In our previous taste-masking study, we found that Acesulfame K (AK) had a better taste-masking effect than other high-efficiency sweeteners for several representative bitter natural drugs in aqueous decoction. Furthermore, we performed a preliminary taste-masking study of AK for representative bitter API Berberine Hydrochloride (BH) and found that it had a good taste-masking effect. We also found that flocculent precipitation was generated in the BH solution, but it was not clear whether it was related to the good taste-masking effect. This study was conducted to explore the taste-masking effect and mechanism of AK on BH.

METHODS

The taste-masking effect of AK on BH was evaluated based on the Traditional Human Taste Panel Method and the electronic tongue evaluation method. DSC, XRD, and molecular simulation techniques were used to explore the mechanism of AK on BH, from the macro level and molecular level, respectively.

RESULTS

When evaluating the taste-masking effect, we found that 0.1% AK had the best taste-masking effect on BH, while higher concentrations had a worse taste-masking effect. DSC and XRD revealed that the flocculent precipitation was a complex AK-BH. Finally, by simulating the binding of AK, BH, and TAS2R46 receptors, we found the unique taste-masking mechanism of AK.

CONCLUSION

The sweet taste stimulus of AK can mask the bitter taste stimulus of BH, and AK can generate AK-BH with BH to reduce the contact between BH and bitter taste receptors. Additionally, it could block the expression of the TAS2R46 receptors.

Detecting the Bitterness of Milk-Protein-Derived Peptides Using an Electronic Tongue

Bitterness is a considerable limiting factor for the application of bioactive peptides in the food industry. The objective of this study was to compare the level of bitterness of milk-protein-derived peptides using an electronic tongue (E-tongue). Liquid milk protein concentrate (LMPC) was prepared from ultra-heat-treated skimmed cow’s milk. It was initially hydrolyzed with different concentrations of trypsin, namely, 0.008 g·L−1, 0.016 g·L−1 and 0.032 g·L−1. In a later exercise, tryptic-hydrolyzed LMPC (LMPC-T) was further hydrolyzed using Lactobacillus bulgaricus and Streptococcus thermophilus. The effect of glucose in microbial hydrolysis was studied. The bitterness of peptides was evaluated with respect to quinine, a standard bittering agent. The level of bitterness of the peptides after microbial hydrolysis of LMPC-T (LMPC-T-F and LMPC-T-FG) was evaluated using a potentiometric E-tongue equipped with a sensor array that had seven chemically modified field-effect transistor sensors. The results of the measurements were evaluated using principal component analysis (PCA), and subsequently, a classification of the models was built using the linear discriminant analysis (LDA) method. The bitterness of peptides in LMPC-T-F and LMPC-T-FG was increased with the increase in the concentration of trypsin. The bitterness of peptides was reduced in LMPC-T-FG compared with LMPC-T-F. The potential application of the E-tongue using a standard model solution with quinine was shown to follow the bitterness of peptides.

Comparison of Sweet–Sour Taste Interactions between Cold Brewed Coffee and Water

Most beverages are complex matrices. Different taste compounds within these matrices interact, and thus affect the perception of the tastes. Sweetness and sourness have generally been known to suppress each other, but often such investigations have focused on aqueous solutions. Investigations into what happens when these known interactions are transferred to more complex solutions are scarce. In this study, we investigated the differences in taste interactions between an aqueous matrix and a cold-brewed coffee matrix. Two sub-studies were conducted. In one, six aqueous samples were evaluated by 152 naïve consumers; in the other six cold-brewed coffee samples were evaluated by 115 naïve consumers. In both studies participants tasted samples with no addition or with addition of either sucrose, citric acid, tartaric acid, or a mix of sucrose and either of the acids. Results showed that the sweetness of sucrose was suppressed by both citric acid and tartaric acid in both matrices. The sourness of both citric acid and tartaric acid was suppressed in the aqueous matrix, but only the sourness of tartaric was suppressed in the coffee matrix. Generally, the suppression was lower in the coffee matrix compared to the aqueous matrix. In conclusion, results from taste interaction studies conducted on aqueous matrices can to some extent, with caution, be interpolated to more complex matrices. Importantly, suppression effects might diminish with an increase in matrix complexity.

Structure determination, bitterness evaluation and hepatic gluconeogenesis inhibitory activity of triterpenoids from the Momordica charantia fruit

Triterpenoids are hypoglycemic substances and flavor components of Momordica charantia L., whether their bitterness correlated with hypoglycemic potential remain unknown. Thus, triterpenoids in M. charantia were isolated by phytochemical methods and identified by spectroscopic analysis. The bitterness levels and hypoglycaemic activity of isolated triterpenoids were evaluated by electronic tongue and hepatic gluconeogenesis assay. Eighteen triterpenoids including two new ones, Momordicoside Y and Z, were identified. Among the six identified bitter triterpenoids, karaviloside III, goyaglycoside C, and momordicoside F2 were bitterer than caffeine (P < 0.05), with caffeine equivalent (CE) values of 289.19, 4.32, and 41.24 mg CE/mg, respectively. Momordicoside Y, charantoside C, momordicoside F1, and momordicoside G could inhibit hepatic gluconeogenesis by 23.9%, 36.2%, 33.4%, 34.4% at 40 μM, respectively. These four compounds could interact with active site of phosphoenolpyruvate carboxykinase in molecular docking simulation. No correlation was observed between hepatic gluconeogenesis inhibitory activity and bitterness of triterpenoids.

A review of emerging technologies enabling improved solid oral dosage form manufacturing and processing

Tablets are the most widely utilized solid oral dosage forms because of the advantages of self-administration, stability, ease of handling, transportation, and good patient compliance. Over time, extensive advances have been made in tableting technology. This review aims to provide an insight about the advances in tablet excipients, manufacturing, analytical techniques and deployment of Quality by Design (QbD). Various excipients offering novel functionalities such as solubility enhancement, super-disintegration, taste masking and drug release modifications have been developed. Furthermore, co-processed multifunctional ready-to-use excipients, particularly for tablet dosage forms, have benefitted manufacturing with shorter processing times. Advances in granulation methods, including moist, thermal adhesion, steam, melt, freeze, foam, reverse wet and pneumatic dry granulation, have been proposed to improve product and process performance. Furthermore, methods for particle engineering including hot melt extrusion, extrusion-spheronization, injection molding, spray drying / congealing, co-precipitation and nanotechnology-based approaches have been employed to produce robust tablet formulations. A wide range of tableting technologies including rapidly disintegrating, matrix, tablet-in-tablet, tablet-in-capsule, multilayer tablets and multiparticulate systems have been developed to achieve customized formulation performance. In addition to conventional invasive characterization methods, novel techniques based on laser, tomography, fluorescence, spectroscopy and acoustic approaches have been developed to assess the physical-mechanical attributes of tablet formulations in a non- or minimally invasive manner. Conventional UV-Visible spectroscopy method has been improved (e.g. fiber-optic probes and UV imaging-based approaches) to efficiently record the dissolution profile of tablet formulations. Numerous modifications in tableting presses have also been made to aid machine product changeover, cleaning, and enhance efficiency and productivity. Various process analytical technologies have been employed to track the formulation properties and critical process parameters. These advances will contribute to a strategy for robust tablet dosage forms with excellent performance attributes.

Prior administration of chocolate improves the palatability of bitter drugs: The Choc-with-Med study

AIM

The paediatric population has a low adherence and acceptance rate of unpalatable medicines. This study aimed to determine whether eating chocolate immediately prior to drug administration would help to mask the bitter taste of a drug. The difference in taste masking efficacy between white, milk and dark chocolate was a secondary measure outcome.

METHODS

A controlled repeated measures crossover taste trial was conducted using a taste panel of 29 young healthy adults who met the criteria to differentiate intensity in bitterness taste. Participants separately tasted solutions of quinine, flucloxacillin and clindamycin using the swill and spit method, singularly and following blinded prior administration of white, milk or dark chocolate. Drug solutions administered without prior chocolate served as controls. Bitterness score for each tasting was recorded using a 5-point scale.

RESULTS

Regardless of chocolate type, mean taste scores with prior chocolate for quinine (range 2.00-2.34), clindamycin (3.72-3.83) and flucloxacillin (3.38-3.45) were all lower than mean scores for respective drugs without chocolate (3.24, 4.75 and 4.28, respectively; P < 0.0001 for all comparisons). Dark chocolate was most efficacious for masking the bitter taste of quinine, but the differences in taste masking efficacy between dark, milk and white chocolates were not statistically significant for flucloxacillin and clindamycin.

CONCLUSIONS

Prior administration of chocolate results in lower perceived bitterness compared to control tastings of quinine, flucloxacillin and clindamycin solutions; however, there is no clear difference in this effect between the dark, milk and white chocolates used in this study.

Temporal profile of low calorie lactose-free ice cream chocolate flavor: temporal dominance sensation and multiple time-intensity analysis

The food industry has a consumer market with growing interest in modified products, so this study aimed to evaluate consumer acceptance and characterize the temporal profile of traditional and lactose-free "low calorie chocolate ice creams". Six different samples were produced: three formulated with traditional whole milk sweetened with sucrose, sucralose and stevia and three formulated with lactose-free whole milk, also sweetened with the same sweeteners. Time-intensity analysis, temporal dominance of sensation and acceptance analysis were performed. The ice cream with lactose-free milk sweetened with stevia had a lower acceptance. The samples sweetened with sucrose were characterized by intensity, duration and dominance of the "sweet" and "chocolate flavor", while the samples sweetened with sucralose were characterized by intensity and duration of the "sweet" stimulus and also by the dominance of the "milk flavor" stimulus. The samples sweetened with stevia were characterized by greater intensity and duration of bitter stimulus, being also characterized by intensity of sweet taste and chocolate flavor. It can be verified that the use of stevia promotes relevant difference in lactose-free ice cream when compared to traditional ice cream, increasing the duration and dominance of bitter taste, as well impacting and decreasing the consumer acceptance. However, the addition of sucralose did not promote significant changes in the profile of both formulations.

Do Gut Microbes Taste?

Gut microbiota has emerged as a major metabolically active organ with critical functions in both health and disease. The trillions of microorganisms hosted by the gastrointestinal tract are involved in numerous physiological and metabolic processes including modulation of appetite and regulation of energy in the host spanning from periphery to the brain. Indeed, bacteria and their metabolic byproducts are working in concert with the host chemosensory signaling pathways to affect both short- and long-term ingestive behavior. Sensing of nutrients and taste by specialized G protein-coupled receptor cells is important in transmitting food-related signals, optimizing nutrition as well as in prevention and treatment of several diseases, notably obesity, diabetes and associated metabolic disorders. Further, bacteria metabolites interact with specialized receptors cells expressed by gut epithelium leading to taste and appetite response changes to nutrients. This review describes recent advances on the role of gut bacteria in taste perception and functions. It further discusses how intestinal dysbiosis characteristic of several pathological conditions may alter and modulate taste preference and food consumption via changes in taste receptor expression.

Comparing the taste-modifying properties of nanocellulose and carboxymethyl cellulose

The taste-modifying properties of nanofibrillar cellulose (NFC) and carboxymethyl cellulose (CMC) are compared for the first time. The samples were prepared in the form of gels, with and without added sweet and bitter taste components. As viscosity itself is known to affect taste perception, the viscosities of NFC and CMC samples were set to the same level as shear rates commonly found in the oral cavity. A trained panel of 10 assessors evaluated the bitterness and sweetness of the samples. Further, the assessors were given an opportunity to describe the samples in free words. The taste-modifying capacities of the thickening agents were at the same level when sweet compounds were added. However, CMC was better able to reduce the bitterness of quinine hydrochloride than NFC, which did not show any bitterness-reduction ability with the compound. This was unexpected, as our previous studies of NFC showed fairly high binding capacity with quinine. The open-ended responses revealed that the NFC-containing samples had an astringent sensation, while certain assessors observed a sensation of saltiness in the CMC samples. This may explain the inability of NFC to mask the bitterness of quinine hydrochloride, as astringency may act as a bitterness enhancer, while saltiness may suppress it. Both thickening agents were perceived as slightly bitter. Our study reveals the need for further assessment of the orosensory properties of NFC, particularly the magnitude and origin of its astringency, before it can be fully utilized in food industry applications.

Characterization of the Human Bitter Taste Receptor Response to Sesquiterpene Lactones from Edible Asteraceae Species and Suppression of Bitterness through pH Control

Vegetables are important sources of nutrients and bioactive compounds; however, their consumption is often insufficient, partly because of unpleasant taste characteristics. This study aimed to investigate the mechanisms underlying bitter taste reception and to develop methods to suppress bitterness. We focused on sesquiterpene lactones found in edible Asteraceae species. HEK293T cells that heterologously expressed human bitter taste receptors (including TAS2R46) together with a chimeric G protein were analyzed using calcium imaging, and cellular responses to four sesquiterpene lactones contained in lettuce were examined. We found that TAS2R46-expressing cells responded most strongly to bitter compounds. The EC₅₀ value of 11β,13-dihydrolactucopicrin was 2.0 ± 0.6 μM, in agreement with the previously reported bitterness threshold of the compound. Adjustment of pH from neutral to weak acidic conditions reduced the response of TAS2R46-expressing cells to sesquiterpene lactones. We demonstrate the possibility of regulating the bitterness of Asteraceae species by controlling the pH.

Can cornelian cherry mask bitter taste of probiotic chocolate? Human TAS2R receptors and a sensory study with comprehensive characterisation of new functional product

Cornelian cherry (Cornus mas L.) fruits are a valuable source of bioactive compounds that are responsible for the perception of bitter taste of chocolate products. The aim of the study was to validate the inhibitory effect of Cornus mas on the TAS2R3 and TAS2R13 bitter taste receptors and to assess the effect of masking the bitter taste of dark chocolate with the help of the sensory panel. Dark chocolate was prepared with an addition of 5% of freeze-dried cornelian cherry fruits and 108 CFU/g of Bacillus coagulans probiotic strains. Effect on the TAS2R receptors was evaluated in specially transfected HEK293T cells, and the inhibition ratio was measured using the calcium release test. Moreover, the total polyphenol content, antioxidant activity and simulated intestinal in vitro digestion were determined for the samples. The tested chocolate products were rich in chlorogenic, caffeic and sinapic acids. The addition of cornelian cherry positively affected the antioxidant activity. The phytochemicals of Cornus mas decreased the TAS2R13 activity by 132% after a 2-minute interaction and, % at the same time, inhibited the TAS2R3 activity by 11.5. Meanwhile, chocolate with the addition of fruit was less bitter according to the sensory panel.

What is the Role of Over 100 Excipients in Over the Counter (OTC) Cough Medicines?

Most medicines are white bitter powders that are formulated as tablets and capsules but cough medicines are an exception where the taste and appearance of the medicine are more important to the patient than the pharmacology of the active ingredient. Excipients are generally defined as any ingredient in a medicine other than the active ingredient. In most medicines excipients play a supportive role in delivering the medicine, but in the case of cough medicines, excipients have more important and complex roles and they can also be the main active ingredient of the cough medicine as menthol, glycerol, and sugars, which are declared as active ingredients. This review searched the United Kingdom electronic medicines compendium (emc) and found over 100 excipients in 60 different liquid formulations of over the counter cough medicines. The excipients were divided into functional groups: sweeteners, thickeners, flavors, colors, antimicrobials, and buffers, and the incidence and function of the different excipients is discussed. When considering the efficacy of a cough medicine, clinicians and pharmacists tend to think of the pharmacology of antitussives such as dextromethorphan or expectorants such as guaifenesin, and they rarely consider the role of excipients in the efficacy of the medicine. This review discusses the functions and importance of excipients in cough medicines and provides some new information for clinicians, pharmacists, and all interested in the treatment of cough when considering the composition and efficacy of a cough medicine.

Platycodon grandiflorum roots: A comprehensive study on odor/aroma and chemical properties during roasting

Platycodon is a ubiquitous plant widely grown in Asia. This study investigated changes in odor/aroma associated sensory attributes and chemical properties in Platycodon grandiflorum roots upon roasting. Amino acid analysis, electronic tongue analysis, chemical property analysis, volatile compound analysis, GC-olfactometry-assisted sensory attributes, and electronic nose analysis were performed. In results, amino acid profiles showed diverse patterns. Electronic tongue analysis somewhat corresponded to the free amino acid profiles. Total phenolic content, antioxidant capacity, and browning intensity significantly increased up to 4 min and slightly decreased afterward. Various pyrazines relevant to roasted odor such as 3-ethyl-2, 5-dimethyl-pyrazine, and 2, 6-dimethyl-pyrazine were generated by roasting. In electronic nose analysis, positive odor parameter significantly increased and potential unpleasant odorants significantly decreased over time. This is believed to be the first study demonstrating overall insight on odor/aroma and chemical characteristics and utilizing objective sensory measures on roasted Platycodon grandiflorum roots for food applications. PRACTICAL APPLICATIONS: This study will be utilized (a) to researchers and food companies who are interested in medicinal foods (b) to individuals and food industry that search for changes in sensory characteristics and chemical changes of foods induced by roasting, and (c) to farmers and crop producers who look for utilization and applications of Platycodon grandiflorum roots as food sources and ingredients.

Effect of fortification with calcium from eggshells on bioavailability, quality, and rheological characteristics of traditional Polish bread spread

Hen eggshells are a rich and natural source of calcium and can serve as a biofunctional food ingredient. Enriching the traditional Polish bread spread (sersmażony) with micronized eggshell is an attractive proposition for consumers who require easily available calcium. The present study aimed to evaluate the use of micronized eggshells as a source of bioavailable calcium in bread spread. The study evaluated the effect of selected biocomponents on calcium bioavailability by using an in vitro digestion model. The enrichment of bread spread with eggshell, lysine, vitamin D₃, and vitamin K enhanced all examined physicochemical variables except water activity. Enrichment with eggshells increased calcium levels >2.5-fold compared with the control sample. As an ingredient of bread spread, lysine is an important rheological factor. The bioavailability of calcium was higher in samples with lysine and vitamin K compared with samples that contained eggshell alone.

Sensing Senses: Optical Biosensors to Study Gustation

The five basic taste modalities, sweet, bitter, umami, salty and sour induce changes of Ca²⁺ levels, pH and/or membrane potential in taste cells of the tongue and/or in neurons that convey and decode gustatory signals to the brain. Optical biosensors, which can be either synthetic dyes or genetically encoded proteins whose fluorescence spectra depend on levels of Ca²⁺, pH or membrane potential, have been used in primary cells/tissues or in recombinant systems to study taste-related intra- and intercellular signaling mechanisms or to discover new ligands. Taste-evoked responses were measured by microscopy achieving high spatial and temporal resolution, while plate readers were employed for higher throughput screening. Here, these approaches making use of fluorescent optical biosensors to investigate specific taste-related questions or to screen new agonists/antagonists for the different taste modalities were reviewed systematically. Furthermore, in the context of recent developments in genetically encoded sensors, 3D cultures and imaging technologies, we propose new feasible approaches for studying taste physiology and for compound screening.

Denatonium enhanced the tone of denuded rat aorta via bitter taste receptor and phosphodiesterase activation

Bitter taste receptors (Tas2rs) initiate a bitter taste signaling involving the activation of taste-specific G protein gustducin and phosphodiesterases (PDEs); it leads to the decrease of cytosolic level of cyclic adenosine monophosphate (cAMP) in taste cells. Recent studies have identified the expression of Tas2rs in a variety of non-lingual tissues including vascular smooth muscle (VSM), pulmonary smooth muscle and airway smooth muscle. The current study aims to determine the expression of Tas2rs and gustducin in rat aortic smooth muscle tissue and to investigate the effect of Tas2rs agonist denatonium on the tone of isolated denuded aorta rings. Here we reported the expression of six subtypes of Tas2r mRNA and the taste receptor-associated G proteins in endothelium-denuded aorta. Immunostaining experiments showed that the protein of gustducin expressed in vascular smooth muscle cells (VSMCs). Furthermore, denatonium increased the tone of freshly isolated denuded aorta rings in a concentration-dependent manner, and the potentiation effect of denatonium was blocked by a Tas2rs antagonist adenosine 5'-monophosphate (5'-AMP), by the cAMP-hydrolyzing PDE inhibitors, and by a cAMP-synthesizing enzyme activator forskolin, respectively. The blockade of G_βγ signaling did not have a negative impact on the denatonium-induced tonic contractions. These findings suggested that the functional Tas2rs and gustducin are expressed in rat aortic smooth muscle and that denatonium might increase the smooth muscle tone through a Tas2rs signaling pathway involving the activation of PDEs.

Effect of electric heating and ice added to the bowl on mainstream waterpipe semivolatile furan and other toxicant yields

OBJECTIVES

We examined mainstream total particulate matter, nicotine, cotinine, menthol, pyrene, carbon monoxide (CO) and semivolatile furan yields from a commercial waterpipe with two methods for heating the tobacco, quick-light charcoal (charcoal) and electric head (electric) and two water bowl preparations: with (ice) and without ice (water).

METHODS

Emissions from a single brand of popular waterpipe tobacco (10 g) were generated using machine smoking according to a two-stage puffing regimen developed from human puffing topography. Tobacco and charcoal consumption were calculated for each machine smoking session as mass lost, expressed as a fraction of presmoking mass.

RESULTS

The heating method had the greatest effect on toxicant yields. Electric heating resulted in increases in the fraction of tobacco consumed (2.4 times more, p<0.0001), mainstream nicotine (1.4 times higher, p=0.002) and semivolatile furan yields (1.4 times higher, p<0.03), and a decrease in mainstream CO and pyrene yields (8.2 and 2.1 times lower, respectively, p<0.001) as compared with charcoal. Adding ice to the bowl resulted in higher furan yields for electric heating. Menthol yields were not different across the four conditions and averaged 0.16±0.03 mg/session. 2-Furaldehyde and 5-(hydroxymethyl)-2-furaldehyde yields were up to 230 and 3900 times higher, respectively, than those reported for cigarettes.

CONCLUSION

Waterpipe components used to heat the tobacco and water bowl preparation can significantly affect mainstream toxicant yields. Mainstream waterpipe tobacco smoke is a significant source of inhalation exposure to semivolatile furans with human carcinogenic and mutagenic potential. These data highlight the need for acute and chronic inhalation toxicity data for semivolatile furans and provide support for the establishment of limits governing sugar additives in waterpipe tobacco and educational campaigns linking waterpipe tobacco smoking behaviours with their associated harm.

Taste masking of propranolol hydrochloride by microbeads of EUDRAGIT® E PO obtained with prilling technique for paediatric oral administration

The purpose of this study was to develop a new solid paediatric formulation for propranolol hydrochloride (PR). This drug is used to treat various paediatric diseases, and recently received clearance to treat haemangioma. However, PR has a bitter salty taste that does not facilitate high rates of compliance among children, especially in liquid formulations. In addition, the solid formulations are designed for adults and often their dosage is not suitable for children that require a flexible dose based on their weight. Therefore, matrix microbeads of EUDRAGIT® E PO containing PR were manufactured to overcome these limitations. Nine different samples were prepared using the prilling-congealing technique with high yield. Using 2 nozzles, 300 and 450 μm (code n), the diameters obtained of microbeads (from 333 to 699 μm) were homogenous and appropriate to be swallowed by children. In this study, the ratio drug:matrix for the microbeads was also examined in detail: 1:25 (F₁), 1:15 (F₂) and 1:10 (F₃) in aqueous and tert-butyl alcohol/aqueous (code t) media. Most of the examined microbeads were characterized by high percentage of encapsulation efficiency (22-100%) and drug loading (22-77 mg of drug per g of matrix) effective for the administration of low and high doses of PR. SEM analysis revealed a matrix with a radial or a spongy structure, with numerous pores that generated soft floating microbeads in aqueous solution. Release studies confirmed a low release and dissolution of the drug in artificial saliva, mainly F_1n > F₁ > F_2nt, and a prompt dissolution in simulated gastric media. Finally, electronic tongue measurements revealed the ability of these formulations to mask the bitter drug taste, especially for the sample with a ratio 1:25 (F_1n and F₁). These samples were chemically and physically stable for six months. In conclusion, the projected microbeads F₁, and F_1n reached the goal of the study, and could be proposed as new solid oral formulations dedicated to use by children.

Potential of benzophenones and flavanones to modulate the bitter intensity of Cyclopia genistoides herbal tea

Variation in the bitter taste of Cyclopia genistoides (honeybush) herbal tea and reported modulation between its major xanthones, mangiferin and isomangiferin, prompted further investigation into the potential modulatory effects of honeybush phenolics. Combinations of crude benzophenone (BF)-, xanthone (XF)-, and flavanone (FF)-rich fractions and their major individual phenolic compounds were analysed by descriptive sensory analysis. The fractions were prepared from a bitter, hot water extract of green C. genistoides. Fraction BF, which is below the bitter threshold (intensity 10 on 100-point scale), enhanced the bitter intensity of XF and FF slightly (p < 0.05), although none of the major individual benzophenones retained this bitter enhancing effect. On the contrary, 3-β-d-glucopyranosyl-4-β-d-glucopyranosyloxyiriflophenone, the major benzophenone in BF, significantly (p < 0.05) decreased the bitter taste of XF, at a low concentration, whereas FF suppressed the bitter intensity of XF and mangiferin, the major xanthone present in XF. Hesperidin, however, had no effect on the bitter intensity of XF. In contrast, (2S)-5-[α-L-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]-naringenin, the major compound of FF, significantly (p < 0.05) enhanced the bitter taste of XF when added at concentrations comparable to that of 'fermented' honeybush tea infusions. The concentration-dependence of these bitter taste interactions may be responsible for the variable bitter intensity of C. genistoides herbal tea.

Glycated Beef Protein Hydrolysates as Sources of Bitter Taste Modifiers

Being averse to bitter taste is a common phenomenon for humans and other animals, which requires the pharmaceutical and food industries to source compounds that can block bitterness intensity and increase consumer acceptability. In this work, beef protein alcalase hydrolysates (BPAH) and chymotrypsin hydrolysates (BPCH) were reacted with glucose to initiate Maillard reactions that led to the formation of glycated or advanced glycation end products (AGEs), BPAH-AGEs and BPCH-AGEs, respectively. The degree of glycation was higher for the BPAH-AGEs (47-55%) than the BPCH-AGEs (30-38%). Analysis by an electronic tongue instrument showed that BPAH-AGEs and BPCH-AGEs had bitterness scores that were significantly (p < 0.05) less than quinine. The addition of BPAH-AGEs or BPCH-AGEs to quinine led to significant (p < 0.05) reductions (up to 38%) in bitterness intensity of quinine. The use of 3% hydrolysate to react with glucose yielded glycated peptides with a stronger ability to reduce quinine bitterness than when 1% was used. Calcium release from HEK293T cells stably expressing the T2R4 human bitter taste receptor was significantly (p < 0.05) attenuated by BPAH-AGEs (up to 96%) and BPCH-AGEs (up to 92%) when compared to the BPAH (62%) and BPCH (3%) or quinine (0%). We concluded that BPAH-AGEs and BPCH-AGEs may be used as bitter taste blockers to formulate better tasting foods.

Perception of Bitter Taste through Time-Intensity Measurements as Influenced by Taste Modulation Compounds in Steviol Glycoside Sweetened Beverages

To limit sugar consumption and maintain sweetness levels in the diet, food and beverage developers often use high potency sweeteners (HPSs) as alternatives. Steviol glycosides are considered a consumer-friendly alternative but they are perceived to have a bitter taste accompanied by sweet and bitter lingering. Recently, taste modulators have been discovered that help to alleviate negative attributes like bitterness of HPSs. To show that taste modulation compounds (TMCs) decrease perceived bitterness associated with steviol glycosides, a trained descriptive panel (n = 9) performed a single-attribute time-intensity (TI) assessment over 2 min. Analysis of Variance (ANOVA) was used to analyze TI curves and curve parameters (AUC, Imax and Tmax). Principal components analysis (PCA) was also used to assess TI curves. Results showed that statistically significant results depended on the analysis method. Bitterness perception was shown to persist less over 2 min for steviol glycosides with TMCs when assessing raw scores and parameters. The same was not found using differences from control curves or weighted curves from PCA. These findings demonstrate that particular TMCs may subtly decrease perceived bitterness of steviol glycosides. However, business objectives of TMC use may dictate what kind of analysis method to use when analyzing perceived bitter perception of TMCs over time.

New insights into the relationship between taste perception and oral microbiota composition

Fairly poor data are available on the relationship between taste perception, food preferences and oral microbiota. In the present study, we investigated the hypothesis that subjects with higher responsiveness to 6-n-propylthiuracil (PROP) might be characterized by a different taste sensitivity and tongue microbiota composition. Indeed, the bacterial metabolism may modulate/enhance the concentration of tastants near the taste receptors, modifying taste perception through a sensorial adaptation mechanism or by a broad range of microbial metabolic pathways. The detection thresholds of sweet, sour, salty and bitter, the Fungiform Papillae Density (FPD) and the composition of bacteria lining the tongue were determined in Supertasters (high PROP responsiveness, ST) and Non-tasters (low PROP responsiveness, NT). An important inter-individual variability was found for all taste stimuli and FPD between the two groups, with NT subjects showing significant higher threshold values and a lower FPD than with STs. We found five bacterial genera whose relative abundances were significantly higher in STs than NTs. This study opens new avenues of research by highlighting associations between parameters usually studied independently.

Hen protein-derived peptides as the blockers of human bitter taste receptors T2R4, T2R7 and T2R14

Bitter sensation is mediated by various bitter taste receptors (T2Rs), thus T2R antagonists are actively explored. Our objective was to look for novel T2R blockers in hen protein hydrolysate (HPH). We screened the least bitter HPH fractions using electronic tongue, and analyzed their peptide sequences and calcium mobilization in HEK293T cells expressing T2Rs. The results showed that the HPH fractions with higher bitterness intensity had higher hydrophobicity, more hydrophobic amino acids, and more positively charged peptides, but fewer known umami peptides. The peptide fractions from the least bitter HPH fraction significantly inhibited quinine bitterness (P < 0.05), and also significantly inhibited quinine- or diphenhydramine-dependent calcium mobilization of HEK293T cells expressing human T2R4, T2R7, or T2R14 (P < 0.05). Among them, the first eluted (least bitter) peptide fraction showed the strongest bitter-inhibitory effect. In conclusion, HPH peptides are the blockers of T2R4, T2R7, and T2R14.

Bitter Taste Impact and Thermal Conversion of a Naringenin Glycoside from Cyclopia genistoides

A naringenin derivative, isolated from Cyclopia genistoides, a bitter tasting herbal tea, especially when in green (unoxidized) form, was identified as (2 S)-5-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]naringenin (1). The compound partially epimerizes to (2 R)-5-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]naringenin (2) when heated at different temperatures (80, 90, 100, 110, and 120 °C) for a prolonged period in a phosphate buffer at pH 5. The fractional conversion model predicted the decrease in the concentration of compound 1 the best. The activation energy of the conversion reaction was calculated as 99.16 kJ mol^-1. Prolonged heating resulted not only in formation of compound 2 but eventually a decrease in its concentration and the formation of another conversion product, ( E)-2'-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]-4',6',4-trihydroxychalcone (3). In contrast, naringin, glycosylated at C-7, remained stable when heated under the same conditions (100 °C for 6 h at pH 5). The bitter intensity of compound 1 was substantially less than that of naringin, both tested at 0.04 mM, a concentration typical of compound 1 in an herbal tea infusion of green C. genistoides. This comparison indicates that the position of the sugar moiety plays an important role in determining both bitter intensity and heat stability of naringenin glycosides.

Taste Perception of Antidesma bunius Fruit and Its Relationships to Bitter Taste Receptor Gene Haplotypes

It was shown more than 40 years ago that the ability to perceive the bitterness of the fruit of the Antidesma bunius tree is inversely correlated with the ability to perceive the well-studied bitter tastant phenylthiocarbamide (PTC). To determine if variants of the TAS2R38 gene, which encodes the PTC taste receptor, or variants in any of the other TAS2R bitter or TAS1R sweet receptor genes account for Antidesma taste perception, we recruited an independent subject sample and examined associations between these taste receptor gene haplotypes and Antidesma perception. Consistent with previous findings, almost none of our subjects who reported Antidesma juice as bitter was a PTC "responder" by previous definitions (i.e. a PTC taster). In our study, of the 132 individuals who perceived PTC as bitter, 15 perceived Antidesma as bitter, although these 15 subjects had very weak bitterness perception scores. Examination of TAS2R38 gene haplotypes showed that, of the subjects who perceive Antidesma as bitter, all carried at least one copy of the TAS2R38 AVI (PTC non-taster) haplotype. However, 86 subjects carried at least one AVI haplotype and failed to perceive Antidesma as bitter. No other TAS2R or TAS1R gene variants showed an association with Antidesma bitter, sweet, or sour perception. Our results show that TAS2R38 haplotypes are associated with differential perception of Antidesma berry juice bitterness, and that all those who perceive this bitterness carry at least one AVI haplotype. This indicates that the AVI haplotype is necessary for this perception, but that additional variable factors are involved.

Bitter taste masking of enzyme-treated soy protein in water and bread

BACKGROUND

Bioactive protein hydrolysates are often very bitter. To overcome this challenge, xylitol, sucrose, α-cyclodextrin, maltodextrin and combinations of these were tested systematically as bitter-masking agents of an enzyme-treated soy protein in an aqueous model and in a bread model. Sensory descriptive analysis was used to reveal the bitter-masking effect of the taste-masking blends on the enzyme-treated soy protein.

RESULTS

In water, xylitol, sucrose and maltodextrin reduced bitterness significantly, whereas α-cyclodextrin did not. No significant difference was observed in bitterness reduction between xylitol and sucrose. Both reduced bitterness significantly more than maltodextrin. No interactions between the taste-masking agents affecting bitterness reduction were found. Clearer bitter-masking effects were seen in the aqueous model compared with the bread model. The bitter-masking effects of α-cyclodextrin and maltodextrin were similar between water and bread. The effect of xylitol and sucrose on bitterness suppression varied between the systems. In water, bitterness was negatively correlated with sweetness. In bread, bitterness was negatively correlated with freshness, and maltodextrin significantly reduced bitterness of the enzyme-treated soy protein and increased freshness.

CONCLUSION

Bitter-masking effects were generally more discernible in the aqueous model compared with the bread model. © 2018 Society of Chemical Industry.

Toward Improving Medication Adherence: The Suppression of Bitter Taste in Edible Taste Films

Bitter taste is aversive to humans, and many oral medications exhibit a bitter taste. Bitter taste can be suppressed by the use of inhibitors or by masking agents such as sucralose. Another approach is to encapsulate bitter tasting compounds in order to delay their release. This delayed release can permit the prior release of bitter masking agents. Suppression of bitter taste was accomplished by encapsulating a bitter taste stimulus in erodible stearic acid microspheres, and embedding these 5 µmeter diameter microspheres in pullulan films that contain sucralose and peppermint oil as masking agents, along with an encapsulated masking agent (sucralose). Psychophysical tests demonstrated that films which encapsulated both quinine and sucralose produced a significant and continuous sweet percept when compared to films without sucralose microspheres. Films with both quinine and sucralose microspheres also produced positive hedonic scores that did not differ from control films that contained only sucralose microspheres or only empty (blank) microspheres. The encapsulation of bitter taste stimuli in lipid microspheres, and embedding these microspheres in rapidly dissolving edible taste films that contain masking agents in both the film base and in microspheres, is a promising approach for diminishing the bitter taste of drugs and related compounds.

Beef Protein-Derived Peptides as Bitter Taste Receptor T2R4 Blockers

The aim of this work was to determine the T2R4 bitter taste receptor-blocking ability of enzymatic beef protein hydrolysates and identified peptide sequences. Beef protein was hydrolyzed with each of six commercial enzymes (alcalase, chymotrypsin, trypsin, pepsin, flavourzyme, and thermoase). Electronic tongue measurements showed that the hydrolysates had significantly ( p < 0.05) lower bitter scores than quinine. Addition of the hydrolysates to quinine led to reduced bitterness intensity of quinine with trypsin and pepsin hydrolysates being the most effective. Addition of the hydrolysates to HEK293T cells that heterologously express one of the bitter taste receptors (T2R4) showed alcalase, thermoase, pepsin, and trypsin hydrolysates as the most effective in reducing calcium mobilization. Eight peptides that were identified from the alcalase and chymotrypsin hydrolysates also suppressed quinine-dependent calcium release from T2R4 with AGDDAPRAVF and ETSARHL being the most effective. We conclude that short peptide lengths or the presence of multiple serine residues may not be desirable structural requirements for blocking quinine-dependent T2R4 activation.

Modulation of the bitterness of pea and potato proteins by a complex coacervation method

The incorporation of novel plant-based proteins into foods is often challenging due to an unacceptable bitter sensation. Typically, a combination of electrostatic and hydrophobic forces contributes to the proteins' bitterness. The current study therefore focuses on the development of electrical properties on cationic plant proteins to reduce their overall bitterness in order to improve the perceived sensorial acceptance. As such, we utilized a simple mixing process to induce complex coacervation of oppositely charged biopolymers under acidic conditions. Pea and potato protein stock solutions were mixed with apple pectin (DE 71%) solutions at various biopolymer ratios to modulate the electrical, rheological, and sensorial properties of the complexes. Whey protein hydrolyzate was used as a control sample. Surface charge measurements revealed a transition from positive to negative values as the pectin concentration was increased regardless of the plant protein, whereas stable dispersions without sedimentation were observed above a critical pectin : protein ratio of 1. Low and intermediate biopolymer ratios (<1) promoted aggregation and led to rapid sedimentation. Sensory evaluation showed that bitterness scores depended on protein type and decreased from pea protein > potato protein > whey protein. Moreover, bitter off-notes were increasingly reduced with increasing pectin : protein ratios; however, high dispersion viscosities above 0.05 Pa s led to undesirable texture and mouthfeel of the biopolymer dispersions. Our results might have important implications for the utilization of novel plant proteins in food and beverage applications.