Quantitation, Organoleptic Contribution, and Potential Origin of Diethyl Acetals Formed from Various Aldehydes in Cognac

Abstract

Cognac wine distillate (WD), especially that produced during aging, is marked by complex and elegant aroma. This work aimed at expanding the knowledge on the Cognac WD aroma by a sensory-guided approach, involving a fractional-distillation technique and gas chromatography coupled to olfactometry and mass spectrometry (GC-O-MS). In doing so, a fruity-odor zone was highlighted in WD extracts that was attributed to the diethyl acetal family. Ten additional diethyl acetals were detected by GC-MS. Next, an assay method was developed and validated for seven of these diethyl acetals. Their detection thresholds were evaluated in a model solution of water/ethanol (60:40, v/v). 1,1-Diethoxy-3-methylbutane was shown to present a significant organoleptic impact because its olfactory-detection threshold (323 μg/L) is lower than its range of concentrations in WD (461 to 3337 μg/L). Given that diethyl acetals result from reactions between ethanol and aldehydes, quantitative correlations between diethyl acetals and corresponding aldehydes were considered.

Profile of volatile organic compounds in musts and cachaças produced by selected Saccharomyces cerevisiae yeast strains

“…Acetals arise during fermentation as the result of the combination of an alcohol molecule with an aldehyde to producing an unstable semiacetal, which then combines with another alcohol molecule to create a stable acetal that does not decompose even during the distillation process (Santiago et al, 2016). The acetals 1,1-diethoxy-3-methylbutane, 1,1-diethoxy-2-methylbutane and 1,1-diethoxyhexane were identified in the present work, as well as in the study of cachaças and cognac (Cardeal et al, 2008;Thibaud;Shinkaruk & Darriet, 2019) The compositions of musts and cachaças are complex and variable, which made the interpretation of the data based on visual analyses inappropriate. Multivariate analysis was used to examine the correlation between the chemical composition of samples and the different fermentative systems tested here (spontaneous and selected strains).…”

Contribution of Volatile Odorous Terpenoid Compounds to Aged Cognac Spirits Aroma in a Context of Multicomponent Odor Mixtures

“…Indeed, a young WD with fresh aromas of fruits, flowers, and vegetal nuances, progressively develops more complex aromas over time, such as woody, spicy, dried fruit, and balsamic notes after 30 years of aging and more. , Among numerous aspects, the contribution of oak wood compounds, the concentration of volatile compounds through the evaporation of ethanol, known as the “angels’ share”, and diverse chemical transformations actively participate in the evolution of these WDs aromas . Paradoxically, while the aromas of fresh and young WD have been studied in depth, − those of aged WDs have been little explored, − thus opening up a broad field of investigation into aging notes.…”

“…The great complexity of the Cognac matrix has been emphasized by the broad diversity of substances detected in this spirit and belonging to numerous chemical classes, such as alcohols, esters, terpenes, aldehydes, ketones, acids, phenols, lactones, diethyl acetals, and sulfur compounds. ,,− The balance between certain representatives of these families has been shown to progress significantly during aging through numerous chemical reactions including oxidation, hydrolysis, esterification, or rearrangement mechanisms . For example, several authors have shown that the amount of fatty acid ethyl esters increased with the time of maturation of WDs. , Various methyl ketones (2-heptanone, 2-nonanone, 2-undecanone, and 2-tridecanone) have been evidenced as pertinent aging markers of WDs. , These compounds have been considered to be the main contributors to Cognac aging aromas (named rancio Charentais ) after that Vidal et al put forward reservations about their direct sensory involvement.…”

Sensorial Impact and Distribution of 3-Methyl-2,4-nonanedione in Cognacs and Spirits

“…The aromas of Cognac and more generally of WD have been largely studied. − The complex fruity and floral aromas are due to the presence of many volatile compounds belonging to several chemical families such as esters, carboxylic acids, terpenes, and aldehydes . We recently established the contribution of diethyl acetals and terpenes to Cognac. , However, the quality of Cognacs is often appreciated after years of aging. It is well known that the maturation allows developing dried fruit, balsamic, woody, and spicy aromas. − Aging time and oak wood contact induce considerable modifications to the composition of Cognacs. ,− For instance, the type of oak (botanical and geographical origins) and the toasting level of staves influence the formation of lactones such as β-methyl-γ-octalactone stereoisomers and vanillin .…”

“…4 We recently established the contribution of diethyl acetals and terpenes to Cognac. 8,9 However, the quality of Cognacs is often appreciated after years of aging. It is well known that the maturation allows developing dried fruit, balsamic, woody, and spicy aromas.…”