Sensory characteristics and their influencing factors for nicotine in different media

In order to investigate the effects of different matrix on the sensory characteristics of nicotine, the sensory characteristics of nicotine at different contents in aqueous solutions, hydrophilic aerosol (propylene glycol) and lipophilic aerosol (glyceryl triacetate) media were systematically evaluated, and the nicotine's flavor detection threshold in each of the medium was also determined. The fractions of free-base nicotine (α_fbn) in aqueous solutions and aerosol condensates with different contents of nicotine were calculated on the basis of pH values or NMR spectra respectively. The effects of lactic acid and menthol on the sensory characteristics, flavor detection thresholds and α_fbn of nicotine in those media were investigated. Furthermore, the sensory effects of nicotine in different aerosols at the same concentration were compared, and the influence of solvent polarity on the gas phase partitioning of nicotine were studied by solid phase micro-extraction gas chromatography-mass spectrometry (SPME-GC/MS). The results showed that: 1) With the adopted sensory evaluation approach, nicotine aqueous solutions mainly caused oral irritation, and their nicotine aerosols created impact on the throat and caused irritation to the nasal cavity and the throat. 2) The flavor detection thresholds of nicotine in aqueous solutions, propylene glycol aerosol and glyceryl triacetate aerosol were 0.072, 0.296 and 0.197 mg/g respectively. 3) In different media, lactic acid reduced the nicotine irritation and increased its detection thresholds by reducing α_fbn significantly. Menthol, however, had similar sensory effects without changing α_fbn. Aerosol media with different polarities influenced the sensory characteristics and flavor detection threshold of nicotine by affecting its gas phase distribution.