Bitterness Intensity Research Articles

Comparison of Ultra-High-Pressure and Conventional Cold Brew Coffee at Different Roasting Degrees: Physicochemical Characteristics and Volatile and Non-Volatile Components

The impact of the roasting degree on ultra-high-pressure cold brew (UHP) coffee remains unclear, although it has been found that UHP technology accelerates the extraction of cold brew (CB) coffee. Therefore, this study investigated the effects of three different degrees of roasting (light, medium, and dark) on the physicochemical characteristics, volatile and non-volatile components, and sensory evaluation of UHP coffee. Orthogonal partial least-squares-discriminant analysis (OPLS-DA) and principal component analysis (PCA) were used to assess the effects of different roasting degrees. The results showed that most physicochemical characteristics, including total dissolved solids (TDSs), extraction yield (EY), total titratable acidity (TTA), total sugars (TSs), and total phenolic content (TPC), of UHP coffee were similar to those of conventional CB coffee regardless of the degree of roasting. However, the majority of physicochemical characteristics, non-volatile components, including the antioxidant capacity (measured based on DPPH and ABTS) and melanoidin, caffeine, trigonelline, and CGA contents increased significantly with an increase in roasting degree. The sensory evaluation revealed that as the roasting degree rose, the nutty flavor, astringency, bitterness, body, and aftertaste intensities increased, while floral, fruity, and sourness attributes decreased. The HS-SPME-GC/MS analysis showed that most volatile components increased from light to dark roasting. Moreover, 15 representative differential compounds, including hazelnut pyrazine, linalool, butane-2,3-dione, and 3-methylbutanal, were identified by calculating the odor-active values (OAVs), indicating that these contributed significantly to the odor. The PCA showed that the distance between the three roasting degree samples in UHP coffee was smaller than that in CB coffee. Overall, the effect of roasting degrees on UHP coffee was less than that on CB coffee, which was consistent with the results of physicochemical characteristics, volatile components, and sensory evaluation.

Quality-Driven Design of Pandan-Flavored Sponge Cake: Unraveling the Role of Thermal Processing on Typical Pandan Aroma.

Pandan (Pandanus amaryllifolius Roxb.) has been used in the production of bakery goods either as a functional ingredient or a natural flavoring that, when roasted, exerts a fragrant rice-like aroma and an attractive green color. This study elucidated the typical aroma compounds from pandan leaves and explored the influence of thermal treatments on their aroma profiles using GC-O-MS, E-nose, and GC-IMS analyses. The effects of formulation and baking conditions on the qualities of pandan-flavored sponge cake were comprehensively evaluated through a holistic approach covering several aspects including cake batter gravity, color, texture, and sensory characteristics. The baking treatment introduced more types of pleasant aromas (9 aromas vs. 17 aromas) and increased the odor intensities of the original volatile compounds, especially for the roasted and steamed rice-like odors. The increased amount of pandan flavoring reshaped the color of the cake crumb (especially for the L* and a* spaces) and significantly decreased the hardness (3.87 N to 1.01 N), gumminess (3.81 N to 0.67 N), and chewiness (13.22 mJ to 4.56 mJ) of the sponge cake. The perceived intensities of bitterness and sweetness can be adjusted by modulating the levels of 2-phenylethanol, 2-methyl-1-butanol, hexyl alcohol, and decanal, along with the total alcohols and aldehydes, due to their significant correlations revealed by correlation heatmap analyses.

Application of multiple dynamic sensory techniques to N-lauroyl amino acids: Exposing the relationship between taste-enhancing properties and chemical structure

This study investigated the taste enhancing effects of N-lauroyl amino acids, including N-lauroyl-phenylalanine, N-lauroyl-tryptophan and N-lauroyl-tyrosine. Sensory results obtained through TDS, TCATA, and TI assessments indicated that all N-Lau-AAs significantly increased the umami intensity and duration of solutions such as simulated chicken broth. Moreover, these compounds masked bitter taste, with LTR showing the most pronounced reduction of bitterness. LP had the effect of enhancing saltiness, whereas LTR and LTY diminished saltiness. Structural analysis revealed a correlation between the chemical structure of N-Lau-AAs and their sensory properties. The presence of carbon‑carbon double bond (CC) was positively correlated with umami intensity and negatively correlated with bitter and salty parameters. Phenolic hydroxyl groups (OH) were negatively correlated with umami intensity and positively correlated with a decrease in bitterness intensity and duration. Overall, this study provides valuable insights into the taste enhancement potential of N-Lau-AAs as taste enhancers in the food industry.

The role of duel hydrolysis of soybean on functional properties and protein digestibility: a sustainable approach.

Protein hydrolysates derived from food sources contains enormous number of peptides which are composed of amino acid possessess various bioactive properties. However, the use of protein hydrolysates as a nutraceutical is hindered due to their unpleasant flavour. The study aims to enhance the biological activity and palatability of protein hydrolysates. In the present study, soybean protein hydrolysate (SPH) was prepared using alcalase for 4 h (control). Modification of hydrolysis (MPH) was carried out by reiterating the hydrolysis of the supernatant obtained after 2 h of hydrolysis using an enzyme to 50% of alcalase during each successive hydrolysis. Samples were characterised by their physio-chemical and functional properties. Furthermore, the effect of modification on the protein digestibility and bitterness intensity using e-tongue was studied. The suppressive effect on retrogradation of corn starch was analysed using texture profile analysis. The results demonstrated increased protein content by 1.6 and 1.9% in MPH compared to SPH and UNH, respectively. MPH showed 1.5- and 1.6-fold higher DH% than SPH before and after gastrointestinal digestion (p < 0.05). A decrease in molecular weight was found in the order of UNH > SPH > MPH. Nevertheless, MPH displayed significantly higher functional properties (p ≤ 0.05). The hardness of retrograded corn starch was significantly reduced in the MPH (1.21N) than SPH (1.55 N) and UNH (1.81N) compared to control (1.71N) during 7-day storage at 4°C (p ≤ 0.05). E-tongue analysis of MPH showed a 4-fold reduction in bitterness than SPH. Modification of hydrolysis of soybean has demonstrated its significance in improved DH% functional properties and palatability. In addition, improved protein digestibility with promising benefits in deferral action on retrogradation of starch over the traditional process of hydrolysis was observed. The outcome of this study contributes to the potential utilisation of MPH as an ingredient in the formulation of nutraceutical products.

Craft Beer Produced by Immobilized Yeast Cells with the Addition of Grape Pomace Seed Powder: Physico-Chemical Characterization and Antioxidant Properties.

The aim of this study was to produce and to characterize craft beer fermented by immobilized yeast cells with the addition of Prokupac grape pomace seed powder (2.5% and 5%), to obtain a beer enriched with phenolic compounds and improved sensory characteristics. The immobilization of the yeast cells was performed by electrostatic extrusion, while the obtained calcium alginate beads were characterized by light and scanning electron microscopy. Phenolic and hop-derived bitter compounds in beer with or without grape pomace seed powder (GS) phenolics were identified using UHPLC Q-ToF MS. The results indicated that GS adjunct significantly shortened the fermentation process of wort and increased the content of phenolic compounds, especially ellagic acid, flavan-3-ols and pro(antho)cyanidins in the final products compared to the control beer. A total of twenty (iso)-α-acids and one prenylflavonoid were identified, although their levels were significantly lower in beers with GS phenolics compared to the control beer. Beers with GS phenolics showed good antioxidant properties as measured by the reduction of ferric ions (FRP) and the scavenging of ABTS•+ and DPPH• radicals. The concentration of immobilized viable yeast cells was higher than 1 × 108 CFU/g wet mass after each fermentation without destroying the beads, indicating that they can be reused for the repeated fermentation of wort. Beers produced with 5% GS added to the wort exhibited the best sensory properties (acidity, astringency, bitterness intensity, mouthfeel, aftertaste and taste), and highest overall acceptability by the panelists. The results showed that grape pomace seed powder present a promising adjunct for the production of innovative craft beer with good sensory properties and improved functionality.

The use of sugar kelp (Saccharina latissima) as a seasoning for popcorn: An investigation of consumer acceptance, sensory perception and emotional response

Increasing consumer demand for health-promoting sustainable food products has led to interest in seaweed. Sugar kelp, Saccharina latissimi, is a rich source of vitamins, minerals, fibre, antioxidants, and protein, but it is underutilized as a food ingredient. Seaweed has been identified as a possible seasoning and could be used in snack foods. As such, the purpose of this study was to evaluate how consumers would use sugar kelp as a seasoning on popcorn. The consumers (n = 95) evaluated popcorn and then were asked to add sugar kelp seasoning and to reevaluate the popcorn. The amount of popcorn consumed, and the amount of seasoning used were recorded. Furthermore, the consumers evaluated the popcorn with and without sugar kelp using hedonic scales, free comment, generalized Labelled Magnitude Scales, as well as emotional response (using the EsSense25 profile). The consumers, on average, used 2.5 g of seasoning and consumed the same amount of both samples (with and without sugar kelp). The addition of sugar kelp decreased the liking scores, increased the intensity of umami and bitterness in the samples, and led to fishy, seaweed, and pepper flavours being perceived. It also led to the reduction of positive emotions and an increased selection of negative emotions. The consumers identified that they are interested in foods containing seaweed, but based on the results of the study, the addition of sugar kelp seasoning needs to be further explored.

One of the major challenges of masking the bitter taste in medications: an overview of quantitative methods for bitterness.

The aim of the present study was to carry out a systematic research on bitterness quantification to provide a reference for scholars and pharmaceutical developers to carry out drug taste masking research. Significance: The bitterness of medications poses a significant concern for clinicians and patients. Scientifically measuring the intensity of drug bitterness is pivotal for enhancing drug palatability and broadening their clinical utility. The current study was carried out by conducting a systematic literature review that identified relevant papers from indexed databases. Numerous studies and research are cited and quoted in this article to summarize the features, strengths, and applicability of quantitative bitterness assessment methods. In our research, we systematically outlined the classification and key advancements in quantitative research methods for assessing drug bitterness, including in vivo quantification techniques such as traditional human taste panel methods, as well as in vitro quantification methods such as electronic tongue analysis. It focused on the quantitative methods and difficulties of bitterness of natural drugs with complex system characteristics and their difficulties in quantification, and proposes possible future research directions. The quantitative methods of bitterness were summarized, which laid an important foundation for the construction of a comprehensive bitterness quantification standard system and the formulation of accurate, efficient and rich taste masking strategies.

Sensory and consumer aspects of sea lettuce (Ulva fenestrata) – impact of harvest time, cultivation conditions and protein level

The green seaweed Ulva fenestrata is a future food candidate, however, both compositional, e.g. protein content, and sensory qualities depend on cultivation and harvest conditions. The aim was to explore sensory qualities of, and consumer attitudes to, U. fenestrata derived from three different cultivation conditions and three harvest times. U. fenestrata was cultivated at sea and in two different land-based tank settings, one mimicking seawater and one with added process water from fishing industry to increase protein content. The seaweed was subjected to sensory analysis performed by an analytical sensory panel and a focus group consisting of consumers. The former assessed the seaweed as dried whole blades (9 samples) and as emulsions (9 samples). Consumers assessed whole blades and a vegan spread enriched with powdered U. fenstrata. All seaweed samples were intensely green; had tastes of umami, salt, bitter, and sour; odours and flavours of grass and fresh seaweed; and had a crispy texture. Cultivation in tanks resulted in a crispier texture than sea cultivation (p<0.001). Protein content increased from 14.4% to 21.6% in tank cultivation with process waters, which increased green colour intensity (p<0.007) and decreased intensity of bitterness (p<0.001). Overall, consumers were positive towards seaweeds as foods.

Exploration of the mechanism of temperature influence on bitter taste of theacrine by activating human bitter taste receptor hTAS2R14

Theacrine, a purine alkaloid derived from Camellia assamica var. kucha, has a distinct bitter taste. Our previous study found the lower recognition threshold of theacrine at 25 °C than 45 °C. This study aims to investigate the bitterness characterizations of theacrine at aforementioned temperatures and its taste perception mechanism. Sensory analysis exhibited higher bitterness intensity for theacrine at 25 °C than 45 °C. Subsequently, flow cytometry was performed to verify the above characterization at the cellular level. It revealed that theacrine could activated the bitter receptor hTAS2R14 and the calcium signal at 25 °C was higher than 45 °C. Ultimately, the interaction mechanism was studied by molecular dynamics simulations, indicating that the conformation of theacrine-hTAS2R14 had a higher binding capacity and better stability at 25 °C. Overall, temperature affected the binding of theacrine to the bitter receptor hTAS2R14, resulting in the stronger bitterness intensity of theacrine at 25 °C than 45 °C.

Taste Sensor Assessment of Bitterness in Medicines: Overview and Recent Topics.

In recent decades, taste sensors have been increasingly utilized to assess the taste of oral medicines, particularly focusing on bitterness, a major obstacle to patient acceptance and adherence. This objective and safe method holds promise for enhancing the development of patient-friendly medicines in pharmaceutical companies. This review article introduces its application in measuring the intensity of bitterness in medicine, confirming the achievement of taste masking, distinguishing taste differences between branded and generic medicines, and identifying substances to suppress bitterness in target medicines. Another application of the sensor is to predict a significant increase in bitterness when medicine is taken with certain foods/beverages or concomitant medication. Additionally, to verify the sensor's predictability, a significant correlation has been demonstrated between the output of a bitter-sensitive sensor designed for drug bitterness (BT0) and the bitterness responses of the human taste receptor hT2R14 from BitterDB (huji.ac.il). As a recent advancement, a novel taste sensor equipped with lipid/polymer membranes modified by 3-Br-2,6-dihydroxybenzoic acid (2,6-DHBA), based on the concept of allostery, is introduced. This sensor successfully predicts the bitterness of non-charged pharmaceuticals with xanthine skeletons, such as caffeine or related compounds. Finally, the future prospects of taste sensors are discussed.

Spatiotemporal analysis of microstructure, sensory attributes, and full-spectrum metabolomes reveals the relationship between bitterness and nootkatone in Alpinia oxyphylla miquel fruit peel and seeds

The Alpinia oxyphylla fruit (AOF) is a popular condiment and traditional Chinese medicine in Asia, known for its neuroprotective compound nootkatone. However, there has not been a comprehensive study of its flavor or the relationship between sensory and bioactive compounds. To address this issue, we examined AOF’s microstructure, flavor, and metabolomic profiles during fruit maturation. The key markers used to distinguish samples included fruit expansion, testa pigmentation, aril liquefaction, oil cell expansion, peel spiciness, aril sweetness, and seed bitterness. A full-spectrum metabolomic analysis, combining a nontargeted metabolomics approach for volatile compounds and a widely targeted metabolomics approach for nonvolatile compounds, identified 1,448 metabolites, including 1,410 differentially accumulated metabolites (DAMs). Notably, 31 DAMs, including nootkatone, were associated with spicy peel, sweet aril, and bitter seeds. Correlational analysis indicated that bitterness intensity is an easy-to-use biomarker for nootkatone content in seeds. KEGG enrichment analysis linked peel spiciness to phenylpropanoid and capsaicin biosynthesis, seed bitterness to terpenoid (especially nootkatone) biosynthesis, and aril sweetness to starch and sucrose metabolism. This investigation advances the understanding of AOF’s complex flavor chemistry and underlying bioactive principle, encapsulating the essence of the adage: “no bitterness, no intelligence” within the realm of phytochemistry.

Consumers' sensory perception and emotional response towards animal and plant‐based soups (familiar food items) with the addition of shio‐koji (an unfamiliar ingredient)

SummaryGlobally, consumers continue to seek out novel foods and ingredients from different cultures and regions. Shio‐koji is a fermented seasoning that is usually made by fermenting rice with koji (Aspergillus oryzae). It has been proposed that shio‐koji can be used as a flavour enhancer of foods. This study investigated consumers' (n = 96; generally unfamiliar with koji) liking (hedonic scales), emotional response (using the EsSense25 profile in check‐all‐that‐apply format), as well as their sensory perception (generalised Labelled Magnitude Scales and free comment) of shio‐koji additions to food items. Participants evaluated three different soups (chicken, vegetable and tomato), a familiar food product, with and without the addition of shio‐koji. The shio‐koji increased the consumers' liking of the vegetable soup and increased their perception of saltiness in the vegetable and tomato soups. The bitterness and sourness intensity of the chicken soup decreased with the addition of shio‐koji, while the sweetness increased. However, the umami taste of all soups was not impacted. The soups with shio‐koji were also associated with positive emotions. During the free comment task, shio‐koji led to an increased mention of meaty attributes to describe the vegetable soup, but the inverse occurred when the participants evaluated the chicken soup. The results indicate that shio‐koji impacted consumer perceptions of both animal‐ and plant‐based soups. Future studies should continue to investigate the use of shio‐koji to enhance the flavour of different food products.

Chitosan-coated nanoliposome: An approach for simultaneous encapsulation of caffeine and roselle-anthocyanin in beverages

The objective of the present research was to develop chitosan-coated nanoliposomes using a modified heating method as a delivery system for simultaneous encapsulation of caffeine and roselle anthocyanin to fortify beverage. Response surface methodology was used to ascertain the optimized formulation, aiming to maximize the encapsulation efficiency, minimize the particle size, and maximize the zeta potential. The liposomes fabricated under the optimized conditions (lecithin to cholesterol ratio of 13 and wall to core ratio of 2.16) showed encapsulation efficiency values of 66.73 % for caffeine and 97.03 % for anthocyanin, with a size of 268.1 nm and a zeta potential of −39.11 mV. Fourier transform infrared spectroscopy confirmed the formation of hydrogen bonds between the polar sites of lecithin and the loaded core compounds. Thermal analysis suggested the successful encapsulation of the caffeine and anthocyanin. Transmission and scanning electron microscopy images confirmed a uniform spherical shape with a smooth surface. Fortifying the model beverage with the liposome and the chitosan-coated nanoliposome revealed higher values of encapsulation efficiency of anthocyanin (70.33 ± 3.11 %), caffeine (86.37 ± 2.17 %) and smaller size (280.5 ± 0.74 nm) of the chitosan-coated nanoliposomes at the end of 60the days. A hedonic sensory test of the fortified beverage with chitosan-coated nanoliposomes confirmed an improvement in the organoleptic properties of the beverage by masking its bitterness (receiving three more sensory scores in perceiving the bitterness intensity). Overall, our study indicates that the high potential of the chitosan-coated nanoliposomes for the simultaneous loading of the caffeine and anthocyanin, as well as their possible application in food and beverage formulations.

Investigation of the quality of Lu'an Guapian tea during Grain Rain period by sensory evaluation, objective quantitative indexes and metabolomics

The harvest date is a crucial factor in determining tea quality. For Lu'an Guapian (LAGP) tea, Grain Rain period (GRP) represents a pivotal phase in the transformation of tea quality. The sensory evaluation, computer vision and E-tongue revealed that the liquor color score, B and G values of tea infusion were increased during GRP, while the astringency, bitterness intensities and the R value of the tea infusion were decreased. Consequently, the tea infusion exhibited a greener hue and the taste became appropriate during GRP. Non-targeted metabolomics revealed that the majority of amino acids and derivatives was reduced during GRP. Furthermore, flavonoids, in particular flavonol glycosides, exhibited considerable variation during GRP. Finally, nine metabolites were identified as markers for quality transformation during GRP by PLS and Random Forest. This study investigated the quality of LAGP teas during GRP and filled the gap in the variation of LAGP tea quality during GRP.

Exploring bitter characteristics of blue honeysuckle (Lonicera caerulea L.) berries by sensory-guided analysis: Key bitter compounds and varietal differences

The taste of blue honeysuckle (Lonicera caerulea L.) berries is wrapped in bitterness, and awareness about the essence of bitterness is lacking. In the current study, 7-ketologanin, sweroside and loganin were isolated and identified as key bitter compounds using sensory-guided analysis. The bitterness thresholds of these compounds were determined to be 11.9 μg/mL, 33.5 μg/mL and 60.2 μg/mL. Subsequently, the differences in bitterness among 16 blue honeysuckle varieties were evaluated. The wild varieties A1 and A2 exhibited the highest bitter intensity. 7-Ketologanin, with the highest concentration of 34.70–37.11 mg/100 g and taste activity values of 29.16–31.18 in A1 and A2, was first identified as a bitter contributor in blue honeysuckle. There was no significant difference in bitter intensity between the reconstitution model and the original sample, confirming the contribution of the three bitter compounds. This study lays the foundation for the bitter improvement and variety selection of blue honeysuckle resources.

Towards an understanding of bitterness in white wines: Contribution of 27 compounds assessed by LC-HRMS and sensory analysis

Whereas bitterness perception can modify the taste balance of white wines, its molecular origin remains largely unclear. This work aimed at determining the influence of a selection of the most cited bitter compounds on the bitterness of commercial dry white wines. Forty-two wines were sensorially characterized by a trained panel and divided into two statistically different groups depending on their bitterness. Twenty-seven bitter compounds were selected and five quantitation methods were developed and validated. The methods were used to measure the levels of all the 27 compounds in dry wine, 25 of them in sweet wine and 22 of them in grape juice. The detected concentrations were generally below the taste detection thresholds. No significant positive correlation between the bitterness intensity of the tasted samples and the concentration of the assayed bitter compounds was observed, suggesting the existence of other markers of bitterness in white wines.

Effect of limited hydrolysis with endopeptidase on bitterness properties of wheat gluten hydrolysates

The application of limited hydrolysis on wheat gluten (WG) has been found to be a highly effective method for improving a wide range of functional properties associated with plant protein. However, the bitter peptides formed during this process have an unpleasant bitterness. To provide a theoretical framework for de-bittering techniques, this study examined the modulation of bitterness intensity in wheat gluten hydrolysates (WGHs) by manipulating enzyme cleavage sites and degree of hydrolysis (DH). It was found that the bitter peptide's release content increased significantly, and the bitterness threshold decreased markedly with increasing DH. Furthermore, the structure-bitterness threshold association of bitter peptides was investigated. The results indicated that peptide segments in molecular weights (MW) from 500 to 1000 exhibited the greatest influence on bitterness threshold compared to peptides with other MWs. The percentage of total hydrophobic amino acid content and position of some hydrophobic amino acids in the amino acid sequence had a significant effect on the bitterness threshold. Finally, 47 peptides were identified by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis. These peptides were mainly small peptides with less than 13 amino acid residues and MW below 1500 Da, and most of them had Q values higher than 5855 J/mol.

Sensory and molecular insights into the bitterness of Wuyi rock tea

Wuyi Rock Tea (WRT) is widely appreciated for its unique rocky flavor and floral essence. However, the characterization of taste attributes, particularly bitterness, in this premium tea remains largely underexplored. This study aims to assess the perception of bitterness in WRT through an integrated approach, including sensory evaluation, phenolic compound analysis, and cell-based calcium imaging assay. Sensory evaluation revealed distinct bitterness intensities among nine selected typical WRT samples. Utilizing UHPLC-Q-Orbitrap-MS, 54 phenolics were tentatively identified, comprising of 24 flavanols, 18 flavonols, and 12 phenolic acids. The cell-based calcium imaging assay revealed diverse intracellular calcium responses and half-maximum effective concentration (EC50) values across the tested samples. Notably, correlation analysis unveiled a strong negative correlation between sensory scores and EC50 values. Furthermore, 11 individual phenolic compounds, such as epigallocatechin gallate and epicatechin gallate, demonstrated significant correlation with sensory scores and bitter taste receptor activation, suggesting their potential role as key contributors shaping the bitter taste perception of WRT. This study provides comprehensive insights into the nuanced bitterness of WRT, bridging sensory and molecular perspectives to enhance our understanding of the taste profile of this premium tea.

Effect of bi-enzyme hydrolysis on the properties and composition of hydrolysates of Manchurian walnut dreg protein

Walnut dreg (WD) active peptides are an important source of dietary antioxidants; however, the products of conventional hydrolysis have limited industrial output owing to poor flavour and low bioactivity. To this end, in this study, we aimed to employ bvLAP, an aminopeptidase previously identified in our research, as well as commercially available Alcalase for bi-enzyme digestion. The flavour, antioxidant activity, and structures of products resulting from various digestion methods were compared. The results showed that the bi-enzyme digestion products had enhanced antioxidant activity, increased β-sheet content, and reduced bitterness intensity from 9.65 to 6.93. Moreover, bi-enzyme hydrolysates showed a more diverse amino acid composition containing 1640 peptides with distinct sequences. These results demonstrate that bi-enzyme hydrolysis could be a potential process for converting WD into functional food ingredients. Additionally, our results provide new concepts that can be applied in waste processing and high-value utilisation of WD.

Thiazolidinediones are Partially Effective Bitter Blockers

PurposeThe bad bitter taste of some medicines is a barrier to overcoming noncompliance with medication use, especially life-saving drugs given to children and the elderly. Here, we evaluated a new class of bitter blockers (thiazolidinediones, TZDs). MethodsIn this study, 2 TZDs were tested, rosiglitazone (ROSI) and a simpler form of TZD, using a high-potency sweetener as a positive control (neohesperidin dihydrochalcone, NHDC). We tested bitter-blocking effects using the bitter drugs tenofovir alafenamide fumarate (TAF), a treatment for HIV and hepatitis B infection, and praziquantel (PRAZ), a treatment for schistosomiasis, by conducting taste testing with 2 separate taste panels: a general panel (N = 97, 20–23 years, 82.5% female, all Eastern European) and a genetically informative panel (N = 158, including 68 twin pairs, 18–82 years, 76% female, 87% European ancestry). Participants rated the bitterness intensity of the solutions on a 100-point generalized visual analog scale. FindingsPerson-to-person differences in drug bitterness were striking; TAF and PRAZ were weakly or not bitter for some people but moderately to highly bitter for others. Participants in both taste panels rated the bitter drugs TAF and PRAZ as less bitter on average when mixed with NHDC than when sampled alone. ROSI partially suppressed the bitterness of TAF and PRAZ, but effectiveness differed between the 2 panels: bitterness was significantly reduced for PRAZ but not TAF in the general panel and for TAF but not PRAZ in the genetically informative panel. ROSI was a more effective blocker than the other TZD. ImplicationsThese results suggest that TZDs are partially effective bitter blockers and the suppression efficacy differs from drug to drug, from person to person, and from panel to panel, suggesting other TZDs should be designed and tested with more drugs and on diverse populations to define which ones work best with which drugs and for whom. The discovery of bitter receptor blockers can improve compliance with medication use.