Development of a new method to understand headspace aroma distribution and explore the pre-sensory level in perceptive interactions involved in red wine fruity aroma expression

Abstract

A part, at least, of red wines fruity expression may be explained by perceptive interactions involving particularly various substituted ethyl esters and acetates present at concentration far below their olfactory threshold, specifically thanks to synergistic effects. 

Wine sensory perception is directly linked to the stimulation of the taster at the level of olfactory epithelium by volatiles. These compounds are liberated from the matrix to the atmosphere, and will then be smelt. From a physico-chemical point of view, these volatiles ability to be released may be evaluated by their partition coefficients, which correspond to the volatile concentration ratio between the liquid and gas phase. Our goal is, through these coefficients determination, to assess if volatile matrix composition is able to impact the volatility of some compounds, and then explain sensory perception, i.eto evaluate what is called the pre-sensorial level impact. 

Up to our works, various experimental methods have already been developed to determine gas-liquid partition coefficients, but were not adapted to red wines fruity aromatic expression context. Recently, we have developed a new method coupling the low-pressure and static headspace gas chromatography to a mass spectrometry (LP-HS-GC-MS) in order to calculate simultaneously main esters partition coefficients, and that, at their wine concentrations. 

This method of partition coefficients determination was used to study potential modifications of headspace aroma distribution and was applied to understand various perceptive interactions previously described by our team. Results revealed that pre-sensory effects may explain the effects observed during sensory analysis. For example, the presence of dimethyl sulfide led to an increase of esters partition coefficients, and therefore their concentration in the headspace what was correlated to the enhancement of the blackberry-fruit notes observed concomitantly. Furthermore, addition of malolactic fermentation by-products (as diacetyle, acetic acid, g-butyrolactone and acetoin) led to a decrease of esters partition coefficients, and thus of their concentration in the headspace, what may explain partly the masking effect of these compounds on fruity notes perception.