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

Sensory research on e-liquid flavors can be performed by means of smelling and vaping. However, data comparing smelling versus vaping e-liquid flavors is 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 non-smokers.Twenty-four young adult smokers (mean age 24.8±9.3) and twenty-four non-smokers (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 Analogue Scale. Pearson correlations within and between smelling and vaping were calculated. Differences between user groups were calculated using t-tests.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 non-smokers.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.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 (i.e. non-users), (2) investigating individuals under legal age for e-cigarette use (i.e. youth and adolescents), (3) investigating brain responses to exposure of e-liquid flavors using fMRI or EEG, and (4) comparing hedonic flavor assessment between adolescent non-users and current smokers to provide support for future regulations on e-liquid flavors.