The impact of temperature and a chemesthetic cooling agent on lingual roughness sensitivity.

Oral tactile sensitivity underpins food texture perception, but few studies have investigated mechanoreception in oral tissues. During food consumption, oral tissues are exposed to a wide range of temperatures and chemical entities. The objective of the present study was to assess the influence of thermal sensations on lingual roughness sensitivity. Just-noticeable difference thresholds (JNDs) were determined using the staircase method for surface roughness from stainless steel coupons (Ra; 0.177-0.465 µm). Thresholds were assessed when cooling or heating the metal stimuli (n = 32 subjects). Compared to the JND threshold obtained at an ambient stimulus temperature (21 °C: 0.055 ±â€…0.010 µm), a cold (8 °C) temperature significantly (P = 0.019) reduced tongue sensitivity (i.e. increased JND) to surface roughness (0.109 ±â€…0.016 µm, respectively) whereas warm and hot temperatures had no significant effect (35 °C: 0.084 ±â€…0.012 µm; 45 °C: 0.081 ±â€…0.011 µm). To assess whether the effect of cooling on roughness thresholds is TRPM8-dependent, we collected roughness thresholds in a second cohort of subjects (n = 27) following the lingual application of the cooling compound Evercool 190 (24.3 µM). Interestingly, when Evercool 190 was used to elicit the cold sensation, lingual roughness JNDs were unaffected compared to the control application of water (EC: 0.112 ±â€…0.016 µm; water: 0.102 ±â€…0.017 µm; P = 0.604). That lingual roughness sensitivity is decreased by cold temperature, but not chemicals evoking cold sensations, suggests the mechanism underpinning thermal modulation is not TRPM8 dependent.

Characterization of the impact of chlorogenic acids on tactile perception in coffee through an inverse effect on mouthcoating sensation.

Coffee "body" is acknowledged by coffee industry professionals to be an attribute which contributes meaningfully to overall coffee quality and is defined as the collective tactile sensation imparted by the beverage. Currently, there is limited knowledge of the chemical compounds that contribute to tactile attributes in coffee. In the present work, coffee body was determined to be comprised of 4 sub-attributes including mouthcoating, astringency, chalkiness, and thickness and the specific constituents contributing to the tactile sensation of mouthcoating were further pursued using sensory-guided fractionation via preparative-scale liquid chromatography. Signal detection-based sensory methodologies were employed to characterize the sensory effects elicited by selected compounds in water and coffee matrices. Two chlorogenic acids, 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were observed to impart subtle but significantly perceptible mouthcoating effects in water and/or coffee. Counterintuitively, sensory perception was inversely related to compound concentration. Complex receptor-ligand interactions or salivary lubrication dynamics are discussed as two potential mechanisms to explain this inverse relationship. Taken together, the outcomes of the present study (1) provide new targets for coffee tactile sensation optimization and modulation, (2) identify a novel dimension of sensory impact for two compounds of the chlorogenic acid family, and (3) present a need for deeper investigation into 3-CQA and 4-CQA mechanisms of sensation.

Understanding the Effects of Smart-Speaker-Based Surveys on Panelist Experience in Immersive Consumer Testing.

Utilizing immersive technologies to reintroduce the environmental context (i.e., visual, auditory, and olfactory cues) in sensory testing has been one area of research for improving panelist engagement. The current study sought to understand whether pairing smart-speaker questionnaires in immersive spaces could positively affect the panelist experience through enhanced ecological validity. To this end, subjects performed an immersive consumer test in which responses were collected using a traditional computer-based survey, a smart-speaker approach incorporating a direct translation of the computer questionnaire into a verbal survey requiring numeric responses, and an optimized smart-speaker survey with alternative question formatting requiring spoken word-based responses. After testing, participants answered the Engagement Questionnaire (EQ) to assess participant engagement during the test, and the System Usability Scale (SUS) survey to understand the ease, and potential adoption, of using the various survey technologies in the study. Results indicated that the traditional computer-based survey was the most engaging (p < 0.001) and usable (p < 0.001), with no differences found between the two smart-speaker surveys (p = 0.803 and p = 0.577, respectively). This suggests that the proposed optimizations for the smart-speaker surveys were not robust enough to influence engagement and usability, and further research is needed to enhance their conversational capabilities.

When considering whether to waste food, consumers focus attention on food label dates rather than phrases.

Date labels have been implicated as a driver of premature discard of food by consumers, which has led to recommendations to change date labels as a way to reduce food waste. However, most proposed date label reform has focused on changing the phrase that accompanies the date on the label, and not how the date is selected. To explore the relative importance of these date label elements, we track consumers' eye movements when evaluating milk container images. When making decisions about the possible discard of milk, participants fixate significantly more on the date printed on the container than on the phrase (e.g., "use by") with >50% of decisions involving no visual fixation on the phrase. This relative inattentiveness to phrases suggests regulation of food date labels should include more focus on the process of choosing label dates.

Capturing high and low levels of participant engagement in sensory and consumer evaluations via a known groups design and an implicit correlate.

Recently developed to characterize consumer engagement during sensory and consumer testing, the Engagement Questionnaire (EQ) can quantify differences in participant engagement; however, the limits of the scale to detect disengagement has not been established. We conducted a known-group experimental design to verify the EQ's ability to differentiate between an engaged and disengaged participant. Participants were randomly assigned to a more engaging (positive condition) and a less engaging sensory task (negative condition). In the positive condition, participants (N = 31) completed 20 tetrad tests; however, stimuli varied in type and difficulty. For the negative condition, participants (N = 28) completed 20 tetrads of the same sucrose concentration to promote a state of helplessness and encourage disengagement with the task. Facial expressions were collected through video recordings, using automatic facial emotion recognition software (FaceReader, Noldus Technology). Accounting for sex differences across the conditions, the EQ successfully discriminated between the positive and negative conditions. When in the positive condition, participants were more actively involved in the task (F1,59 = 23.99, p < 0.001), and experienced higher levels of purposeful intent (F1,59 = 11.10, p = 0.002) and affective value (F1,59 = 26.03, p < 0.001). Participants were more emotive in general, and experienced increased happiness (F1,42 = 22.24, p < 0.001), anger (F1,42 = 12.10, p = 0.001) and disgust (F1,42 = 4.33, p = 0.04) as well as lower levels of a neutral expression (F1,42 = 24.88, p < 0.001) in the positive condition. Now validated via known-groups analysis, the EQ can confidently differentiate a greater range of engagement. Such an instrument allows for a deeper understanding of participant engagement and its potential effect on data quality.

Identification of subthreshold chlorogenic acid lactones that contribute to flavor instability of ready-to-drink coffee.

Flavor instability of ready-to-drink (RTD) coffee during storage negatively impacts product quality. Untargeted liquid chromatography/mass spectrometry (LC/MS) analysis was applied to identify chemical compounds that degraded during storage and impacted the flavor attributes of RTD coffee. LC/MS chemical profiles of non-aged and aged coffee samples were modeled against the degree of difference sensory scores by orthogonal partial least squares with good fit (R2Y = 0.966) and predictive ability (Q2 = 0.960). The top five predictive chemical features were subsequently purified by off-line multidimensional Prep-LC, revealing ten coeluting chlorogenic acid lactones (CGLs) compounds that were identified by LC/MS and nuclear magnetic resonance (NMR). The concentrations of eight CGLs significantly decreased in the coffee during the 4-month storage. Sensory recombination testing revealed the degradation of 3-O-caffeoyl-É£-quinide and 4-O-caffeoyl-É£-quinide significantly impacted the flavor stability of RTD coffee at subthreshold concentrations.

Identification of Non-Volatile Compounds Generated during Storage That Impact Flavor Stability of Ready-to-Drink Coffee.

Coffee brew flavor is known to degrade during storage. Untargeted and targeted LC/MS flavoromics analysis was applied to identify chemical compounds generated during storage that impacted the flavor stability of ready-to-drink (RTD) coffee. MS chemical profiles for sixteen RTD coffee samples stored for 0, 1, 2, and 4 months at 30 °C were modeled against the sensory degree of difference (DOD) scores by orthogonal partial least squares (OPLS) with good fit and predictive ability. Five highly predictive untargeted chemical features positively correlated to DOD were subsequently identified as 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid. The increase in the six acidic compounds during storage was confirmed by sensory recombination tests to significantly impact the flavor stability of RTD coffee during storage. A decrease in pH, rather than an increase in total acidity, was supported to impact the coffee flavor profile.

Identification of Non-Volatile Compounds That Impact Flavor Disliking of Whole Wheat Bread Made with Aged Flours.

Whole wheat flour has a shorter shelf life than refined wheat flour due to off-flavor development. An untargeted liquid chromatography/mass spectrometry (LC/MS) flavoromics approach was applied to identify compounds that negatively impact the flavor liking in whole wheat bread made from aged flours. The chemical profiles of thirteen breads made from aged flours were obtained using LC/MS and modeled by orthogonal partial least squares (OPLS) to predict flavor liking. Top predictive chemical features (negatively correlated) were identified as pinellic acid (9S,12S,13S-trihydroxy-10E-octadecenoic acid), 12,13-dihydroxy-9Z-octadecenoic acid, and 1-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine. The sensory analysis confirmed the three compounds increased the bitterness intensity of the bread samples. The formation of the trihydroxy fatty acid bitter compound, pinellic acid (9S,12S,13S-trihydroxy-10E-octadecenoic acid), was impacted by the lipoxygenase activity of the flour; however, there was no influence on the formation of 12,13-dihydroxy-9Z-octadecenoic acid or 1-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine. Additionally, the concentrations of all bitter compounds were significantly higher in bread made from aged flour versus non-aged flour.

Elucidation of a lingual detection mechanism for high-viscosity solutions in humans.

While perception of high-viscosity solutions (η > 1000 cP) is speculated to be linked to filiform papillae deformation, this has not been demonstrated psychophysically. Presently, just-noticeable-viscosity-difference thresholds were determined using the forced-choice staircase method and high-viscosity solutions (η = 4798-12260 cP) with the hypotheses that the tongue would be chiefly responsible for viscosity perception in the oral cavity, and that individuals with more, longer, narrower filiform papillae would show a greater acuity for viscosity perception. Subjects (n = 59) evaluated solutions in a normal, "unblocked" condition as well as in a "palate blocked" condition which isolated the tongue so that only perceptual mechanisms on the lingual tissue were engaged. Optical profiling was used to characterize papillary length, diameter, and density in tongue biopsies of a subset (n = 45) of participants. Finally, psychophysical and anatomical data were used to generate a novel model of the tongue surface as porous media to predict papillary deformation as a strain-detector for viscosity perception. Results suggest that viscosity thresholds are governed by filiform papillae features. Indeed, anatomical characterization of filiform papillae suggests sensitivity to high-viscosity solutions is associated with filiform papillae length and density (r = 0.68, p < 0.00001), but not with diameter. Modelling indicated this is likely due to a reciprocal interaction between papillae diameter and fluid shear stress. Papillae with larger diameters would result in higher viscous shear stress due to a narrower gap and stronger fluid-structure interaction, but a larger-diameter papilla would also deform less easily.

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.

Context effect of environmental setting and product information in acceptability testing of tea and cola: A study comparing sensory engagement in a traditional sensory booth and a study commons.

Sensory evaluation of food relies heavily on the eating context. The objective of this study was to determine how the context effect, created from differences in environmental setting and product information, affects consumer's acceptability of two types of beverages. Participants of this study rated five ready-to-drink tea products and five diet cola products on a 9-point hedonic scale. Environmental setting differences were created by altering testing locations, and product information differences were created by serving the same samples with or without product name and image. Self-reported sensory engagement was measured in each location. Tea samples showed significantly higher appearance liking ratings in the sensory booth location as well as higher flavor liking ratings when product information was provided. Cola samples did not show a significant effect of testing location but did show a significant product information by sample interaction, where well-established brands received higher ratings when product information was provided. Overall, results were product-specific; testing location does not appear to have a large influence on hedonic scores for certain beverages, and the impact of product information varies largely depending on the product type and brand. The laboratory sensory booth setting provided higher panelist engagement overall. Additional research on the combination of external context and meal, sample, or social context is needed to fully explore the effect of eating context in sensory tests. PRACTICAL APPLICATION: Findings from this study can help the food industry comprehend how test location may impact results of acceptability testing of different beverage products, both in terms of hedonic scores and sensory engagement. Results of this study also evidence the influence of sample information on product acceptability and how this influence differs based on the type of beverage and the popularity of the brand tested.

Non-food odors and the duality of smell: Impact of odorant delivery pathway and labeling convention on olfactory perception.

The olfactory system encompasses two perceptual pathways (orthonasal and retronasal) that activate the same receptors in the olfactory epithelium yet are thought to elicit different perceptions. Presently, a novel matching paradigm was employed using a non-food flavor set with low retronasal familiarity (honeysuckle, lavender, rose, and jasmine) to evaluate the effect of odor type on the Duality of Smell. Additionally, the influence of cognitive strategies used by subjects was assessed by manipulating the naming convention seen by the subjects: familiar (Honeysuckle, Lavender, Rose, Jasmine), unfamiliar (Inodora, Pedunculata, Beggeriana, Didymum), and generic (A, B, C, D). Subjects were presented with a reference, either in a vial (orthonasal delivery, ON) or a 2 oz. cup (retronasal delivery, RN) and instructed to match the same aroma from four unknowns, evaluated either by the same delivery route (congruent, e.g., ON-ON, RN-RN) or different route (incongruent, e.g., ON-RN, RN-ON) than the reference evaluation. All possible combinations of orthonasal and retronasal delivery for the reference and unknowns (e.g. ON-ON, RN-RN, ON-RN, RN-ON) were assessed by all subjects. Matching performance and signal detection measures indicated that, on average, subjects performed significantly better in the congruent conditions than in the incongruent conditions. These results suggest perceptual quality of aromas is route dependent and extend the Duality of Smell hypothesis to samples with low retronasal familiarity such as non-food odors. Labeling convention also had an impact on performance but, surprisingly, not in the direction anticipated. Indeed, as the information contained in the label decreased from familiar to generic reference names, performance increased. Moreover, depending on the labeling convention used, certain aromas were easier to match than others. The present research suggests odorant matching is a function of stimulus quality, cognitive strategy, and labeling convention.

Application of the Engagement Questionnaire (EQ) to compare methodological differences in sensory and consumer testing.

Understanding the panelist experience in sensory and consumer testing is a critical step in methodological development that improves data reliability. Therefore, the Engagement Questionnaire (EQ) was recently developed to characterize consumer engagement during sensory and consumer testing and to provide a novel and translatable metric for researchers to compare methodologies. Presently, we assessed whether relatively minor methodological manipulations to common consumer testing paradigms impact panelist engagement. Specifically, panelist engagement was measured in three scenarios: over the course of a two-day consumer hedonic evaluation (Experiment 1), with differing Just-About-Right (JAR) questionnaire formats in an evaluation (Experiment 2), and with a time pressure element imposed during a consumer acceptability test (Experiment 3). In Experiment 1, subjects remained actively involved in the evaluation across both days of testing, however, they found more purpose and affective value in the task after the second day. In Experiment 2, changing the structure of JAR questions did not impact subject's level of active involvement with the task, yet certain JAR question structures did elicit higher purposeful intent and affective value in subjects. Surprisingly, in Experiment 3, subjects were less actively involved in the time-pressure condition; purposeful intent and affective value were consistent across both conditions. Overall, the EQ was able to resolve differences in panelists' perceived level of engagement across all the experimental manipulations, aiding in discussion regarding the effect even minor manipulations might have on consumer panelists. The EQ is a valuable asset to methodological development and enables comparisons of differing sensory and consumer methodologies.

Do Caucasian American and South Asian Indian cultural groups differ in sensitivity to capsaicin? A study designed to control for chili pepper affinity.

Although different cultural groups are known to vary in their tolerance for hot chili peppers, the influence of factors such as cultural background and upbringing on sensitivity to compounds in spicy food is unclear. A study was designed to investigate sensitivity differences to capsaicin between Caucasian American and South Asian Indian cultural groups while controlling for general chili pepper affinity. The two cultural groups were selected to match on metrics related to chili pepper use and liking. Subjects were exposed to a capsaicin (100 ppm) stimulus on the tongue, cheek, hard palate, and lip and rated the intensity of irritation every 30 s, over a 10-min period. Overall sensitivity to capsaicin in the oral cavity did not differ between the groups, nor were responses different between the groups depending on the oral cavity area stimulated. These data suggest a limited role of cultural attributes on capsaicin sensitivity between Caucasian Americans and South Asian Indians. The methods and findings here provide subject recruitment insight and guidance on effectively designing a sensory study to answer perceptual questions regarding specific subject groups. PRACTICAL APPLICATION: This study design provides a model for researchers interested in utilizing sensory testing to answer questions about subject groups. Although the objective of this study regarded sensitivity differences across two cultural groups, alterations in the subject matching process used presently could be easily implemented to investigate sensitivity across other differing subject characteristics of interest.

Assessing regional sensitivity and desensitization to capsaicin among oral cavity mucosae.

This study aimed to determine perceptual response differences and characterize desensitization to capsaicin over time across several oral cavity mucosae- the tongue, cheek, hard palate, and lip. For each region, subjects rated the intensity of capsaicin and a vehicle control over a 10-minute period. Following a rest period, capsaicin was reapplied on each pretreated area and subjects indicated which side felt more irritated then rated each side every 30 seconds, over 3.5 minutes. Results from the initial task indicated significantly greater irritation on the tongue than hard palate, hard palate than cheek and lip, but no significant differences between the cheek and lip. Time to max intensity was delayed on the hard palate compared to the tongue, cheek, and lip. Desensitization, as indicated by a significant proportion of subjects choosing the vehicle-pretreated side over capsaicin-pretreated side as having stronger irritation, was exhibited on the tongue and hard palate, but not the cheek and lip. Given these data, a secondary experiment that utilized a higher capsaicin concentration was conducted on the cheek and lip only. Results showed significantly higher overall irritation on the lip than the cheek. Desensitization was exhibited on both areas, although the extent was greater on the lip. Based on differences in sensitivity and the extent of desensitization among these areas, these results indicate oral cavity mucosae respond to, but are impacted differently by, capsaicin exposure.

Development of a "pure-tactile" assessment of edge discrimination in the hands and oral cavity.

Oral cavity edge perception acuity relative to the fingertip has previously been evaluated by the utilization of cognitively-loaded, stereognostic methods. However, with the lack of connection of the tongue to the visual association cortex, there is concern the superior acuity of the fingertip may be attributable to the cognitive component of the task. Here, perception acuity is evaluated by assessing participants' (n=29) just-noticeable-difference threshold for edge sharpness tiles using the finger and tongue. As expected, the pure-tactile task found greater acuity in the tongue, suggesting the cognitive component of the previous task confounded results and should not be used.

Impact of bitter tastant sub-qualities on retronasal coffee aroma perception.

The impact of different bitter taste compounds on the retronasal perception of coffee aroma was investigated. A sorted napping experiment was carried out on thirteen compounds at iso-intense bitter concentrations. Differences in perceptual bitter sub-qualities among the compounds were reported by Multidimensional Scaling (MDS) and Multiple Factor Analysis (MFA) analyses. Seven exemplar compounds were further selected to investigate the impact of taste sub-qualities on cross-modal flavor interactions. In general, the different bitter compounds, when paired with a coffee aroma isolate, significantly modified the perception of the retronasal coffee aroma profile. Interestingly, the three bitter compounds endogenous to coffee had the most similar impact on the coffee aroma profile. Further sensory analysis of these sample sets indicated no significant effect of the bitter compounds on the orthonasal perception. Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the volatile composition of the samples headspace also indicated negligible impact of the bitter compounds on aroma release. Altogether evidence of cross-modal interactions occurring at a higher cognitive level were demonstrated in a complex food sample, supporting the importance of multi-modal sensory integration on flavor perception.

Chemogenic Subqualities of Mouthfeel.

Mouthfeel refers to the physical or textural sensations in the mouth caused by foods and beverages that are essential to the acceptability of many edible products. The sensory subqualities contributing to mouthfeel are often chemogenic in nature and include heat, burning, cooling, tingling, and numbing. These "chemesthetic" sensations are a result of the chemical activation of receptors that are associated with nerve fibers mediating pain and mechanotransduction. Each of these chemesthetic sensations in the oral cavity are transduced in the nervous system by a combination of different molecular channels/receptors expressed on trigeminal nerve fibers that innervate the mouth and tongue. The molecular profile of these channels and receptors involved in mouthfeel include many transient receptor potential channels, proton-sensitive ion channels, and potassium channels to name a few. During the last several years, studies using molecular and physiological approaches have significantly expanded and enhanced our understanding of the neurobiological basis for these chemesthetic sensations. The purpose of the current review is to integrate older and newer studies to present a comprehensive picture of the channels and receptors involved in mouthfeel. We highlight that there still continue to be important gaps in our overall knowledge on flavor integration and perception involving chemesthetic sensations, and these gaps will continue to drive future research direction and future investigation.