Mechanisms explaining the role of viscosity and post-deglutitive pharyngeal residue on in vivo aroma release: A combined experimental and modeling study.

The objective of this study was to analyse the viscosity effect of liquid Newtonian products on aroma release, taking human physiological characteristics into account. In vivo release of diacetyl from glucose syrup solutions varying widely in viscosity (from 0.7 to 405mPas) was assessed by five panelists using Proton Transfer Reaction Mass Spectrometry (PTR-MS). The physicochemical properties of the solutions and the physiological parameters of subjects were experimentally measured. In parallel, a mechanistic model describing aroma release while eating a liquid food was developed. Model predictions based on the characteristics of the glucose syrup solution were invalidated when compared to in vivo measurements. Therefore, the assumption that the post-deglutitive pharyngeal residue was considerably diluted with saliva was introduced into the model. Under this hypothesis, the model gives a satisfactory prediction of the in vivo data. Thus, relevant properties to be considered for in vivo release were those of product-saliva mixes.