Understanding the impact of cooling and warming compounds on in-mouth aroma release from flavoured aqueous systems: the unexpected effect of menthol.

Menthol and capsaicin, known for their distinctive cooling and warming trigeminal sensations, respectively, are widely utilised as food flavour ingredients globally. Despite their well-documented effects on sensory perception, the impact of these compounds, individually and in combination, on in-mouth aroma release remains poorly understood. In this study, four flavoured aqueous model systems were formulated with either capsaicin, menthol, or in combination to compare against a control. Each model system contained five aroma compounds selected with diverse physicochemical properties: butyl formate, ethyl butyrate, isoamyl acetate, limonene and citral. The in vitro results of static and dynamic headspace analysis by atmospheric pressure chemical ionisation-mass spectrometry (APCI-MS) showed no impact of capsaicin or menthol on the gas-liquid partitioning equilibria of the aroma compounds. While capsaicin had no significant impact on in-mouth aroma release from 20 healthy participants, the presence of menthol significantly increased the average maximum aroma release (Imax) of ethyl butyrate, citral and limonene to 130%, 113% and 184% respectively, compared to the control (100%). The results of area under curve (AUC) indicated that the total in-mouth release of limonene released from the capsaicin system was similar to the control at 108%, but a dramatic increase to 225% was observed in the menthol system. This significant increase was also observed in the menthol system for citral and butyl formate to 125% and 144% respectively. For the first time, this study demonstrated that menthol significantly enhanced the persistence of in-mouth aroma release, offering valuable insight into its application in the flavour, oral care and food industries.