Flavor science in the context of research on electronic cigarettes.

Thousands start smoking or vaping daily, despite long-standing efforts by public health authorities to curb initiation and use of nicotine containing products. Over the last 15 years, use of electronic nicotine delivery systems has increased dramatically, with a diverse range of products on the market, including pod-based, disposable, and refillable electronic cigarettes (eCigs). Originally intended for harm reduction and smoking cessation, eCigs may encourage nicotine use among never smokers, given the vast range of appealing flavors that are available. To better understand abuse liability and to facilitate appropriate regulations, it is crucial to understand the science of flavor, and flavor perception within the context of eCig use. Here, we (a) provide a brief primer on chemosensory perception and flavor science for addiction and nicotine researchers, and (b) highlight existing some literature regarding flavor and nicotine use, with specific attention given to individual differences in perception, and interaction between different sensory modalities that contribute to flavor. Dramatic increases in use of eCigs highlights the importance of flavor science in contemporary addiction research, both with regards to public health and regulatory efforts. Other recent work summarizes findings on flavored e-liquids and eCig use, but none have focused explicitly on chemosensory processes or flavor perception as they relate to appeal and use of such products. We argue flavor science needs to be considered as perceptual and behavioral phenomena, and not merely from analytical, toxicological and pharmacological perspectives; we help address this gap here.

Flavor and product messaging are the two most important drivers of electronic cigarette selection in a choice-based task.

Electronic cigarette use-vaping-is increasingly popular. Various product factors may influence an individual's choice of e-cigarette. To provide an evidence base for e-cigarette regulation, a better understanding of the role different product attributes play in product preferences is needed. Here, we used conjoint analysis to quantify different factors that influence e-cigarettes choices, including flavors, nicotine level, customizability, or use of e-cigarettes to manage appetite/food craving. Young adults completed a set of choice-based conjoint tasks online. Choice Based Conjoint analysis (CBC) was used to determine utility scores for each attribute. Young adults (n = 587) who vaped at least once per week were included in analyses; gender differences were explored. Flavor was the most important attribute (48.1%), followed by product messaging (21.0%) and nicotine level (15.3%). Within flavor, confectionery and fruit flavors had the highest utility scores, while classic menthol and tobacco flavors had the lowest. Men and women differed in flavors, nicotine levels, and product messaging that appealed most. Among young adults who vape weekly, flavor is the most important factor in e-cigarette preferences. Gender also factors into e-cigarette preferences, especially for preferred nicotine level. Understanding why individuals choose particular e-cigarette products will help inform public health efforts and policy making.

Harsh and Sweet Sensations Predict Acute Liking of Electronic Cigarettes, but Flavor Does Not Affect Acute Nicotine Intake: A Pilot Laboratory Study in Men.

INTRODUCTION: Electronic cigarette use is increasing in popularity, and thousands of flavors are available. Adolescent vaping rates in the United States have nearly doubled in the past year. Unlike combustible tobacco, added flavors are not currently regulated for some types of electronic cigarette products. Here, we investigated the role of flavor in electronic cigarette liking and acute intake. METHODS: Men (n = 39) aged 18-45 vaped in a controlled laboratory setting after being randomized to one of four e-liquids: 6 mg nicotine/mL cherry, 18 mg/mL cherry, 6 mg/mL chocolate, or 18 mg/mL chocolate. They completed several questionnaires, and vaped ad libitum for 10 minutes. After the first puff, participants rated sensations (sweetness, bitterness, coolness, harshness/irritation) on general labeled magnitude scales (gLMS) and rated overall liking on a generalized hedonic scale. Once the 10-minute session ended, participants made another set of ratings. RESULTS: Liking was generally stable across the vaping session and liking varied substantially across the four conditions. Across all conditions, sensory ratings predicted liking: harshness/irritation was negatively associated with first puff liking, whereas perceived sweetness was positively associated with first puff liking. First puff liking associated with increased amount of e-liquid vaped, but not total nicotine intake. Participants appeared to titrate their nicotine intake regardless of assigned condition. CONCLUSION: Flavored e-liquids affect acute liking ratings, but not acute nicotine intake. IMPLICATIONS: These data suggest individuals who regularly vape may titrate their nicotine intake, regardless of flavor, and contrary to expectations, acute liking did not predict total nicotine intake. However, more-liked flavors may potentially make higher nicotine levels more tolerable by adding pleasant sensations directly, rather than by perceptual masking that reduces aversive sensations.

Individual Differences in Thresholds and Consumer Preferences for Rotundone Added to Red Wine.

Rotundone is an aromatic compound found in the skin of some grapes (e.g., Shiraz, Noiret) that contributes peppery notes to wines made with these varieties. There may be a specific anosmia for rotundone, as some individuals are unable to detect it even at high concentrations, despite otherwise normal olfaction. This may affect perception of and preference for rotundone-containing wines. Here, we report rotundone detection thresholds (orthonasal n = 56; retronasal n = 53) and rejection thresholds (n = 86) in red wine for a convenience sample of non-expert consumers in Pennsylvania. Focus groups were conducted to better understand consumer attitudes and preferences for rotundone. Ortho- and retronasal detection thresholds were nearly identical (140 v. 146 ng/L). Roughly 40% of our sample was anosmic to rotundone, extending evidence for a specific anosmia to a North American cohort. As ortho- and retronasal thresholds were extremely similar, future work on rotundone can rely on orthonasal assessment. In our participants, added rotundone was generally disliked, and in focus groups, the concept of a 'peppery' wine was not appealing. Winemakers need to carefully consider biological and attitudinal segmentation when making and marketing peppery wines. Further work is needed to identify the genetic basis for this anosmia.

Vanillin modifies affective responses to but not burning sensations from ethanol in mixtures.

Vanillin may modulate perception of noxious oral stimuli via TRP receptor interactions; separately, vanillin has also been shown to have top-down influences on flavor perception. Here, we ask whether added vanillin decreases the perceived burn of ethanol either via peripheral or cognitive mechanisms. Participants rated the burn of ethanol with 0, 16, and 160 ppm vanillin. In studies 1 (n = 102) and 2 (n = 82), participants wore nose clips and rated the burn of 8% and 16% ethanol (study 1) or 32% and 48% ethanol (study 2). In study 3 (n = 65), participants were able to breathe freely and rated liking and perceptual qualities of 8% and 32% ethanol at each vanillin level. Vanillin showed no significant effect on ratings of burn or smoothness, but did increase perceived sweetness (p < .001) and liking (p = .004) in study 3. These data suggest vanillin does not modulate ethanol burn via TRP receptor mediated interactions, but may shift hedonic responses to ethanol via top-down processes.

Self-reported Smoking Status, TAS2R38 Variants, and Propylthiouracil Phenotype: An Exploratory Crowdsourced Cohort Study.

TAS2R38 gene variants, which confer sensitivity to specific bitter tastants (e.g., 6-n-propylthiouracil), have been repeatedly associated with lower alcohol use via greater bitterness perception, but research exploring TAS2R38 variation in relation to smoking shows mixed results. In both, the working hypothesis is that 1 or more copies of the functional allele increases bitterness and may provide a barrier to early use. Such a barrier to initiation may, conceivably, manifest as differential rates of current use across diplotypes. Here, an age-diverse convenience sample (n = 886) of Denver Museum of Nature and Science guests was used to explore cross-sectional relationships between TAS2R38 diplotype, self-reported tobacco use (current, former, never smokers), and a rapid measure of 6-n-propylthiouracil phenotype (bitterness of filter paper discs). TAS2R38 diplotypes were determined by Sanger sequencing. After excluding rare diplotypes, data from 814 participants were analyzed. A mix of current (~10%), former (25%), and never smokers (65%) were included. As expected, there was a relationship between TAS2R38 diplotype and 6-n-propylthiouracil bitterness. However, contrary to our hypothesis, there was no evidence of a relationship between diplotype and smoker status among participants with common TAS2R38 diplotypes. Notably, we observed a relationship between of 6-n-propylthiouracil bitterness and smoking status, but the effect was opposite of what was expected: current smokers perceived higher (not lower) bitterness than never smokers. When all the various factors (diplotype, age, sex, and smoking status) were included in ANOVA, all remained predictive of 6-n-propylthiouracil bitterness. Reasons for greater phenotypic bitterness among current smokers are unknown and merit further study.

The effect of litter separation on methamphetamine-conditioned place preference in post-partum dams.

Methamphetamine (METH) abuse among women has recently increased to levels comparable to those observed in men. Although studies using animal models of addiction have begun to include more female subjects, examination of the effects of drugs of abuse on post-partum females is currently lacking. This is especially important in light of the significant hormonal and neurobiological changes that accompany pregnancy and rearing experiences. Furthermore, stress in a known factor in addiction vulnerability and the post-partum experience in the clinical population can be highly stressful. Here, we utilized the conditioned place preference paradigm to investigate the conditioned rewarding effects of METH either in virgin rats or in dams exposed to brief separation (15 min) or long separation (180 min) from the litter. We found that females in the brief separation group showed significantly greater METH conditioned place preference compared with both the long separation and virgin groups. No differences were found in locomotor activity during the conditioning sessions. These findings suggest that peripartum experience and brief litter separation may enhance the rewarding effects of METH.