Sensory evaluation of e-liquid flavors by smelling and vaping yields similar results.

Abstract Introduction Sensory research on e-liquid flavors can be performed by means of smelling and vaping. However, data comparing smelling versus vaping e-liquid flavors are lacking. This study aims to investigate if smelling could be an alternative to vaping experiments by determining the correlation for hedonic flavor assessment between orthonasal smelling and vaping of e-liquids, for smokers and nonsmokers. Methods Twenty-four young adult smokers (mean age 24.8 ± 9.3) and 24 nonsmokers (mean age 24.9 ± 7.7) smelled and vaped 25 e-liquids in various flavors. Participants rated liking, intensity, familiarity, and irritation on a 100-mm Visual Analog Scale. Pearson correlations within and between smelling and vaping were calculated. Differences between user groups were calculated using t tests. Results Correlation coefficients between smelling and vaping based on mean group ratings were 0.84 for liking, 0.82 for intensity, 0.84 for familiarity, and 0.73 for irritation. Means of the within-subjects correlation coefficients were, respectively, 0.51, 0.37, 0.47, and 0.25. Correlations between smelling and vaping varied across individuals (ranging from −0.27 to 0.87) and flavors (−0.33 to 0.81). Correlations and mean liking ratings did not differ between smokers and nonsmokers. Conclusions The strong group-level correlations between orthonasal smelling and vaping e-liquid flavors justify the use of smelling instead of vaping in future research. For example, smelling could be used to investigate differences in e-liquid flavor liking between (potential) user groups such as nicotine-naïve adolescents. The more modest within-subject correlations and variation across individuals and flavors merit caution in using smelling instead of vaping in other types of experiments. Implications This study supports the use of orthonasal smelling (instead of vaping) e-liquids to measure hedonic flavor perception in some studies where vaping would be inappropriate or not feasible. Examples of research situations where smelling e-liquids may be sufficient are (1) investigating nicotine-naïve individuals (ie, nonusers), (2) investigating individuals under legal age for e-cigarette use (ie, youth and adolescents), (3) investigating brain responses to exposure of e-liquid flavors using functional magnetic resonance imaging or electroencephalogram, and (4) comparing hedonic flavor assessment between adolescent nonusers and current smokers to provide support for future regulations on e-liquid flavors.


Panel characteristics
* Among the group of non-smokers, there were 2 ex-smokers who reported to have quit smoking for 6 and7 years, respectively.
** Inhalation and exhalation approach were asked retrospectively.

Mean liking ratings for smokers and non-smokers
Mean liking ratings among smokers was higmhest for mint (69.9±3.0) followed by peppermint (67.8±2.6) in smelling, and for peppermint (68.5±4.2) and mint (65.4±4.9) in vaping (see Table   S2). Among non-smokers, mean liking was highest for lemon ( Table S2: Mean liking ratings for smokers and non-smokers. Data were collected on a 0 to 100 mm VAS. Within each group, the two highest ratings are marked in green and the two lowest ratings are marked in red. Differences in mean flavor liking between smokers and non-smokers were not significant (p>0.05).

Correlations between smelling and vaping among smokers and non-smokers
For smokers, the correlation coefficients based on the mean smelling and vaping ratings were 0.78 for liking, 0.76 for intensity, 0.83 for familiarity, and 0.65 for irritation. For non-smokers, the correlation coefficients based on the mean smelling and vaping ratings were 0.86 for liking, 0.85 for intensity, 0.84 for familiarity, and 0.75 for irritation. The correlations did not significantly differ between smokers and non-smokers.

Correlations between smelling and vaping for liking
The correlations for liking between smelling and vaping were positive for all individuals, except for two subjects (R=-0.27 and R=-0.06). The positive correlation coefficients ranged from 0.06 to 0.87. The correlation coefficients for liking of the individual e-liquid flavors between smelling and vaping (n=25) were all positive, except for whiskey (R=-0.33). The positive correlations ranged between 0.08 (caramel) and 0.81 (watermelon).