Perceived Bitterness Intensity Research Articles

Characterization of bitter-tasting and antioxidant activity of dry-hopped beers.

Bitter flavors and antioxidant activities are critical characteristics and indicators, respectively, of beer quality. To gain a better understanding of dry-hopped beer's bitterness, this work comprehensively evaluated the perceived bitterness intensity and bitterness attributes from aspects of beer aroma and non-volatile bitter compounds using sensory analysis under two conditions: (i) with and (ii) without nose clips. To quantify bitter and volatile compounds, the work conducted chromatographic analyses: high-performance liquid chromatography (HPLC), ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and gas chromatography-mass spectrometry (GC-MS). Simultaneously, this work assessed the antioxidant activity of commercially dry-hopped beers. First, dry-hopped beer in this study contained abundant non-volatile bitter compounds (hop bitter acids, polyphenols and flavonoids), and aroma was validated using HPLC, UPLC-MS and GC-MS methods. Moreover, the bitter-tasting perception test findings demonstrated that many dry-hopped beers had a higher bitterness intensity when evaluated without a nose clip, whereas this phenomenon was adverse in several ale beers. Additionally, the 'lingering' and 'harsh' characteristics were diminished when beer aroma was blocked out (with nose clip) for dry-hopped beer. Meanwhile, most dry-hopped beers had greater antioxidant activity than ale beers (P < 0.05). This work revealed the bitterness complexity of dry-hopped beer; besides non-volatile bitter compounds, beer aroma had an impact on the perceived bitterness intensity and attributes, and dry-hopped beer had a relatively intense antioxidant capacity. This study facilitated the development of a detailed knowledge about the assessment of bitter-tasting perceptions in dry-hopped beers and provided a basis for the development of functional beer benefiting human health. © 2022 Society of Chemical Industry.

Repeated exposure to epigallocatechin gallate solution or water alters bitterness intensity and salivary protein profile

Polyphenols, bitter and astringent compounds present in many healthy foods, induce varied sensory responses across individuals. These differences in liking and flavor intensity may be attributable, in part, to differences in saliva. In the current study, we tested the effect of repeated consumption of a bitter polyphenol (epigallocatechin gallate, EGCG) solution on perceived bitterness intensity and salivary protein composition. We hypothesized exposure to EGCG would cause an increase in concentrations of salivary proteins that inhibit bitterness of polyphenols. We also hypothesized that participants with higher habitual polyphenol, specifically the flavanols, intake would experience less bitterness from EGCG solutions than those with low habitual intake, and that the high flavanol consumers would be more resistant to salivary alterations. We also tested whether bovine milk casein, a food analog for salivary proteins that may suppress bitterness, would decrease bitterness intensity of the EGCG solution and mitigate effects of the intervention. Participants (N = 37) in our crossover intervention adhered to two-week periods of daily bitter (EGCG) or control (water) solution consumption. Bitterness intensity ratings and citric acid-stimulated saliva were collected at baseline and after each exposure period. Results indicate that bitterness intensity of the EGCG solution decreased after polyphenol (bitter EGCG) exposure compared to control (water) exposure. Casein addition also decreased bitterness intensity of the EGCG solution. While there was not a significant overall main effect of baseline flavanol intake on solution bitterness, there was an interaction between intervention week and baseline flavanol intake. Surprisingly, the higher flavanol intake group rated EGCG solutions as more bitter than the low and medium intake groups. Of proteins relevant to taste perception, several cystatins changed in saliva in response to the intervention. Interestingly, most of these protein alterations occurred more robustly after the control (water) exposure rather than the bitter (EGCG) exposure, suggesting that additional factors not quantified in this work may influence salivary proteins. Thus, we confirm in this study that exposure to bitterness suppresses ratings of bitterness over time, but more work needs to establish the causal factors of how diet influences salivary proteins.

Identification of non-volatile compounds that negatively impact whole wheat bread flavor liking

Untargeted LC–MS flavoromic analysis was utilized to identify chemical compounds that impact consumer liking of whole wheat bread. Chemical fingerprints of thirteen whole wheat breads were modeled against consumer flavor liking scores by orthogonal partial least squares (OPLS) with good fit (R2Y = 0.98) and predictive ability (Q2 = 0.95). The four most predictive features (negatively correlated) were identified as 9S,12S,13S-trihydroxy-octadec-10E-enoic acid (pinellic acid), 9S,12S,13S-trihydroxy-octadeca-10E,15Z-dienoic acid, 8R*,9R*,10S*-trihydroxy-octadec-6Z-enoic acid, and 1-(octadeca-9Z,12Z-dienoyl)-sn-glycero-3-phosphocholine. Sensory validation studies including bitter threshold determination and recombination tests confirmed the contribution of these compounds to the perceived bitterness intensity of the bread samples and the overall negative impact on flavor liking. Lipoxygenase activity of the flour was reported to have a significant impact on the formation of the three bitter compounds (trihydroxy fatty acids) in the bread samples.

Identification of inhibitors of pinellic acid generation in whole wheat bread

Bitterness is a common aversive flavor attribute of foods associated with low consumer acceptance. Untargeted LC–MS flavoromic profiling was utilized to identify endogenous compounds that influence the generation of the bitter compound 9,12,13-trihydroxy-trans-10-octadecenoic acid (pinellic acid) during bread making. A diverse sample set of wheat germplasm was chemically profiled. The corresponding pinellic acid concentrations after dough formation were modeled by orthogonal partial least squares (OPLS) with good fit (R2Y = 0.8) and predictive ability (Q2 = 0.6). The most predictive feature (negatively correlated), postulated to interfere with the biosynthetic pathway, was identified as schaftoside, an apigenin di-C-glycoside. Recombination experiments involving the addition of schaftoside to flour prior to breadmaking resulted in a 26% decrease in pinellic acid formation and significantly lower perceived bitterness intensity in whole wheat bread. This work provides novel understanding of bitter generation pathways in wheat products and new strategies to improve flavor profiles and consumer acceptability.

Identification of coffee compounds that suppress bitterness of brew

Untargeted LC–MS flavoromic profiling was utilized to identify compounds that suppress bitterness perception of coffee brew. The chemical profiles of fourteen brew samples and corresponding perceived bitterness intensities determined by descriptive sensory analysis were modeled by orthogonal partial least squares (OPLS) with good fit (R2Y > 0.9) and predictive ability (Q2 > 0.9). Ten chemical markers that were highly predictive and negatively correlated to bitter intensity were subsequently purified by multi-dimensional preparative LC–MS to conduct sensory recombination testing and/or confirm compound identifications by NMR. Three of the ten compounds evaluated, namely 4-caffeoylquinic acid, 5-caffeoylquinic acid, and 2-O-β-d-glucopyranosyl-atractyligenin were identified as bitter modulators in coffee, and significantly decreased the perceived bitterness intensity of the brew.

Preference for and sensitivity to flavanol mean degree of polymerization in model wines is correlated with body composition

Bitterness and astringency (dryness) are characteristic sensory attributes of flavanol-rich foods. The degree of polymerization (DP) of flavanols influences their bitter and astringent sensations. Smaller DP compounds can enter the papillae on the tongue, eliciting a bitter response. Larger DP compounds are sterically inhibited from entering papillae and instead interact with oral proteins, cause precipitation, and elicit astringent sensations. Previous research has indicated that bitterness preference is related to health status, density of fungiform papillae on the tongue, and sensitivity to bitter compounds such as 6-n-propyl-thiouracil (PROP). The purpose of this study was to examine trends in liking, bitterness intensity, and astringency intensity of wine-like products with flavanols of different DP using a consumer sensory panel. Participants (n = 102) were segmented by phenotypes: body fat percentage (BF%), body mass index (BMI), PROP sensitivity, and stated bitter food preference. Differences in wine liking, perceived bitterness intensity, and astringency intensity were observed between three model wine samples of varying flavanol mean degrees of polymerization (mDP, i.e. the average size (polymer length) of flavanol compounds in a mixture). Specifically, with increased mDP, overall liking and bitterness liking decreased, with concurrent increased perception of bitterness and astringency intensity. Greater differences between phenotypes were observed when participants were segmented by BF% and BMI classification, than when segmented by PROP sensitivity classification. Reduced ability to detect differences in bitterness and astringency were noted in participants of higher weight status. Overall, these data suggest that weight status in adults is a greater predictor of liking of flavanol-rich foods than bitterness sensitivity (as determined by PROP classification), and that reduced perception of bitterness and astringency associated with weight gain may impact selection and preference for these foods.

Preference for and Sensitivity to Flavanol Mean Degree of Polymerization in Model Wines Is Correlated with Body Composition (P06-100-19)

ObjectivesIt is known that the degree of polymerization (DP) of flavanol compounds influences the perceived bitter and astringent sensations of flavanol-rich foods. Previous research has indicated that preference for bitterness and astringency is related to health status (i.e., obesity) and sensitivity to bitter compounds such as 6-n-propyl-thiouracil (PROP). The objective of this study was to examine trends in liking, bitterness intensity, and astringency intensity of wine-like products with distinct flavanols of different DP in a consumer sensory panel when consumers were differentiated by phenotype. MethodsRecruited panelists (n = 102) were segmented into different phenotypes based on body fat percentage (BF%), body mass index, PROP sensitivity, and stated preference for bitter foods. Differences in overall product liking, perceived bitterness intensity, and astringency intensity were observed between the three wine samples formulated to contain varying flavanol mDP. ResultsConsidering the panelists altogether without segmentation, overall liking and bitterness liking decreased with increasing flavanol mDP, with concurrent increased perception of bitterness and astringency intensity. When looking at specific phenotypes, subjects of higher BMI and BF% showed significantly reduced ability to detect differences in bitterness and astringency intensity. Interestingly and unexpectedly, PROP sensitivity and self-reported bitterness preference did not significantly correlate with liking and intensity trends based on flavanol mDP. ConclusionsOverall, these data suggest that BF% and BMI are greater predictors of liking and sensitivity to flavanol-rich foods compared bitterness sensitivity and self-reported bitterness liking. Reduced perception of bitterness and astringency associated with weight gain may impact selection and preference for these foods. Funding SourcesFunding for this work was provided in part by the Virginia Tech Translational Obesity Research Graduate Interdisciplinary Research Program and the Virginia Tech Agricultural Experiment Station, and the Hatch Program, USDA-NIFA.

Taste Exam: A Brief and Validated Test.

The emerging importance of taste in medicine and biomedical research, and new knowledge about its genetic underpinnings, has motivated us to supplement classic taste-testing methods in two ways. First, we explain how to do a brief assessment of the mouth, including the tongue, to ensure that taste papillae are present and to note evidence of relevant disease. Second, we draw on genetics to validate taste test data by comparing reports of perceived bitterness intensity and inborn receptor genotypes. Discordance between objective measures of genotype and subjective reports of taste experience can identify data collection errors, distracted subjects or those who have not understood or followed instructions. Our expectation is that fast and valid taste tests may persuade researchers and clinicians to assess taste regularly, making taste testing as common as testing for hearing and vision. Finally, because many tissues of the body express taste receptors, taste responses may provide a proxy for tissue sensitivity elsewhere in the body and, thereby, serve as a rapid, point-of-care test to guide diagnosis and a research tool to evaluate taste receptor protein function.

Modification of perceived beer bitterness intensity, character and temporal profile by hop aroma extract

The effect of hop aroma on perceived bitterness intensity, character and temporal profile of beer was investigated. A hop aroma extract was added at 3 levels (0, 245, 490mg/L) to beers at low, medium and high bitterness. Beers were evaluated for perceived bitterness intensity, harshness, roundedness and linger by a trained panel using a rank-rating technique at each bitterness level, with and without nose clips. The use of nose clips enabled the olfactory aspect to be decoupled from taste and mouthfeel aspects of bitterness perception. Results showed significant modification of perceived bitterness in beer by hop aroma depending on the inherent level of bitterness. These modifications were mainly driven by olfaction – in an example of taste-aroma interactions, as well as certain tactile sensations elicited by the hop aroma extract in the oral cavity. At low bitterness, beers with hop aroma added were perceived as more bitter, and of ‘rounded’ bitterness character relative to those without hop aroma. When judges used nose clips, this effect was completely eliminated but the sample was perceived to have a ‘harsh’ bitterness character. Conversely, at high bitterness, even when nose clips were used, judges still perceived beers containing hop aroma to be more bitter. These increases in bitterness perception with nose clips indicates the stimulating of other receptors, e.g. trigeminal receptors by hop aroma extract, which in tandem with the high bitterness, cause perceptual interactions enhancing bitterness intensity and also affecting bitterness character. Bitterness character attributes such as ‘round’ and ‘harsh’ were found to significantly depend on bitterness and aroma levels, with the second level of aroma addition (245mg/L) giving a ‘rounded’ bitterness in low bitterness beers but ‘harsh’ bitterness in high bitterness beers. The impact of aroma on temporal bitterness was also confirmed with time-intensity measurements, and found to be mostly significant at the highest level of hop aroma addition (490mg/L) in low bitterness beers. These findings represent a significant step forward in terms of understanding bitterness flavour perception and the wider impact of hop compounds on sensory perception.

Identification of bitter modulating maillard-catechin reaction products.

The influence of thermally induced reaction products of a known dietary bitter compound, catechin, on bitterness perception was investigated. Catechin was reacted in low-moisture simple Maillard models (200 °C for 15 min) consisting of glycine and a reducing sugar (D-glucose, D-xylose, or D-galactose). Based on liquid chromatrography-mass spectrometry (LC-MS) isotopic labeling techniques, eight reaction products were identified and subsequently structurally elucidated by tandem LC-MS/MS and two-dimensional NMR analysis; six were report to be flavan-3-ol-spiro-C-glycosides reaction products. One of the spiro products was reported to significantly suppress the perceived bitterness intensity of a caffeine solution. Additionally, this specific spiro product was further identified in cocoa and reported to increase in concentration during bean roasting.

Extra virgin olive oil bitterness evaluation by sensory and chemical analyses

An experimental investigation was performed on blend extra virgin olive oils (EVOOs) from different cultivars and EVOO from different olive monovarieties (Coratina, Leccino, Maiatica, Ogliarola) with the aim to evaluate the possibility of estimating the perceived bitterness intensity by using chemical indices, such as the total phenol content and the compounds responsible for oil bitterness measured spectrophotometrically at 225nm (K225 value), as bitterness predictors in different EVOO. Therefore, a bitterness predictive model, based on the relationship between the perceived bitterness intensity of the selected stimuli and the chosen chemicals parameters has been built and validated. The results indicated that the oil bitterness intensity could be satisfactorily predicted by using the K225 values of oil samples.

Reducing bitter taste through perceptual constancy created by an expectation

The influence of a perceptual expectation, based on the first bite of a model product, on the perception of the taste of subsequent bites is investigated for bitter taste. A model product (chocolate ice cream) consisting of three regions of differing concentrations of a bitter compound (theobromine) was evaluated by a sensory panel using a multiple-bite Time–Intensity (TI) method. TI bitterness parameters were compared to those obtained with the model product containing the same amount of bitter compound but distributed homogeneously through the product. The relevant parameters of the resulting TI bitterness curves, i.e. the area under the curve, the time to return to zero, the overall maximum intensity, show that when the first bite is of a low bitter intensity, the perception of subsequent regions in the product assimilate towards a lower perceived bitterness intensity.

Heritability and genetic covariation of sensitivity to PROP, SOA, quinine HCl, and caffeine.

The perceived bitterness intensity for bitter solutions of propylthiouracil (PROP), sucrose octa-acetate (SOA), quinine HCl and caffeine were examined in a genetically informative sample of 392 females and 313 males (mean age of 17.8 +/- 3.1 years), including 62 monozygotic and 131 dizygotic twin pairs and 237 sib pairs. Broad-sense heritabilities were estimated at 0.72, 0.28, 0.34, and 0.30 for PROP, SOA, quinine, and caffeine, respectively, for perceived intensity measures. Modeling showed 1) a group factor which explained a large amount of the genetic variation in SOA, quinine, and caffeine (22-28% phenotypic variation), 2) a factor responsible for all the genetic variation in PROP (72% phenotypic variation), which only accounted for 1% and 2% of the phenotypic variation in SOA and caffeine, respectively, and 3) a modest specific genetic factor for quinine (12% phenotypic variation). Unique environmental influences for all four compounds were due to a single factor responsible for 7-22% of phenotypic variation. The results suggest that the perception of PROP and the perception of SOA, quinine, and caffeine are influenced by two distinct sets of genes.

Relationship of papillae number to bitter intensity of quinine and PROP within and between individuals

Subjects were asked to assess the bitterness of one 6- n-propyl-2-thiouracil (PROP) and two quinine HCl (QHCl) concentrations presented via filter papers of varying sizes. The number of taste papillae stimulated by these filter papers was counted in each individual. Whole mouth sensitivity to PROP was determined in a separate session. In support of other demonstrations of spatial summation, these data indicated that perceived bitterness intensity increased as a function of area of stimulation within subjects. Between subjects, there was a significant trend for the perceived bitterness of PROP to increase with the lingual density of fungiform papillae, although this trend was highly variable and was only demonstrable among those who showed at least moderate sensitivity to PROP. On the other hand, the number of stimulated fungiform papillae failed to account for individual differences in perceived bitterness of QHCl.

The effect of sweeteners on bitter taste in young and elderly subjects

The purpose of this study was to quantify the degree of reduction in perceived bitterness by sweeteners at both threshold and suprathreshold concentrations of bitter compounds. Detection and recognition thresholds were determined for six bitter compounds (caffeine, denatonium benzoate, magnesium chloride, quinine hydrochloride, sucrose octaacetate, and urea) in the absence and presence of several suprathreshold concentrations of five sweeteners. The sweeteners were: sucrose, aspartame, sodium saccharin, mannitol, and sorbitol. Polycose was also tested along with the sweeteners. The degree to which bitter thresholds were affected by the addition of sweeteners was dependent on the chemical classification of the sweeteners and their concentrations. In general, the natural sweeteners, sucrose, mannitol, and sorbitol, were more effective than the noncaloric sweeteners, aspartame and sodium saccharin, in elevating the detection and recognition thresholds of the bitter compounds. A sweetness intensity approximating that of 6% sucrose (0.175 M sucrose) or greater was required to elevate thresholds. For elderly subjects, sweeteners did not significantly elevate thresholds for denatonium benzoate and sucrose octaacetate. The degree to which sorbitol and sucrose can decrease the perceived bitterness intensity of suprathreshold concentrations of the six bitter compounds was also determined. The concentrations of sweeteners and bitter compounds were selected to be of moderate to high subjective intensity. The levels of sweeteners used in the mixtures were: sucrose (none, 0.946 M, and 2.13 M) and sorbitol (none, 2.1 M, and 3.68 M). Both sweeteners significantly reduced the bitterness ratings of almost every concentration of the six bitter compounds. The greatest reductions in bitterness were 87.0% for 0.192 μM denatonium benzoate mixed with 2.13 M sucrose and 84.7% for 1.8 M urea mixed with 3.68 M sorbitol.

PRINCIPAL COMPONENT ANALYSIS OF TIME‐INTENSITY BITTERNESS CURVES1

ABSTRACTPerceived bitterness in drinks is known to fade slowly over time. Time‐Intensity curves are a means of studying this fading process. K subjects record the perceived bitterness intensity by moving a slider on a monitor using a mouse. Usually average TI‐curves are calculated to give a representation of the TI‐curve for one particular object. The problem is that there often are large individual differences, so the average TI‐curve is not always a good representation. An alternative is to perform a Principal Component Analysis on the matrices of objects by individual TI‐curves for each object. The resulting, so‐called, Principal Time Intensity Curves (PTIC's) are better representations than the average curves. Often the PTIC's for the different products are hard to distinguish. In this case a noncentered PCA of the matrix with curves gives results which show more differences between the products.