Aroma characterization of aged cognac spirits: contribution of volatile terpenoid compounds

Abstract

Cognac spirit aromas result from the presence of a wide variety of volatile odorous compounds associated with the modalities of distilled spirit elaboration and during aging. Indeed, these odorous compounds play an essential role in the finesse and complexity of the aged Cognac. However, very few studies have been done on this subject especially regarding to aging notes with exotic wood (sandalwood) and balsamic descriptors. The aim of this work is to improve knowledge of these aromatic nuances.  

To answer this question, a sensory-guided approach was used after selection by an expert panel of aged Cognac spirits. After solvent extraction, HPLC fractionation was used in order to evidence fractions of interest recalling specific aromatic nuances of aged Cognac. Doing so, it was possible to select some HPLC fractions presenting interesting notes of aged Cognac and recalling particularly exotic wood and balsamic descriptors. Their contribution was demonstrated by reconstitution and omission tests with all HPLC fractions. 

 Then the GC-O/MS analysis of the selected fractions allowed to detect odorous zones and identify associated compounds. First, various well known compounds representative of terpenoids family were highlighted as geraniol, α-terpinene, nerol, α-terpineol, 1,8-cineole (eucalyptol) and particularly piperitone which was not cited in Cognac. These compounds were quantified and their detection thresholds were carried out. 

An insight of their evolution during aging shown that geraniol, α-terpinene, α-terpineol and 1,8-cineole concentrations increased while spirit were more aged, while nerol tend to decrease. However aging had no impact on piperitone. The impact of wine distillation with lees was also particularly considered and the quantification of these compounds showed an impact of this parameter of the elaboration process. 

 The organoleptic impact of 1,8-cineole was highlighted in Cognac at concentration over its detection threshold. While continuing the GC-O analysis and its coupling to mass spectrometry, aroma nuances of sandalwood, were particularly noticeable. Thus, other molecules were identified through the sensory-guided method. They were santalol with sandalwood nuances and α-campholenal with tea and sandalwood nuances, both of which were related to sandalwood, respectively a sesquiterpene and a monoterpene. These new identifications thus open up a large field of investigation concerning the terpenoids family and their sensory impact within the aged Cognac matrix.