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

Article abstract of DOI:10.1021/acs.jafc.9b01084

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.

Full text of DOI:10.1021/acs.jafc.9b01084

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Chemistry and Biology of Aroma and Taste
Quantitation, organoleptic contribution and potential origin
of diethyl acetals formed from various aldehydes in Cognac.
Fannie Thibaud, Svitlana Shinkaruk, and Philippe Darriet
J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.9b01084 • Publication Date (Web): 19 Feb 2019
Downloaded from http://pubs.acs.org on February 25, 2019
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Page 1 of 31
Journal of Agricultural and Food Chemistry
Quantitation, organoleptic contribution and potential origin of diethyl
acetals formed from various aldehydes in Cognac.
Fannie Thibaud,† Svitlana Shinkaruk,‡ † and Philippe Darriet†
†
Univ. Bordeaux, Unité de recherche Œnologie, EA 4577, USC 1366 INRA, ISVV, 33882
Villenave d’Ornon cedex, France
‡
Univ. Bordeaux, ISM, Institut des Sciences Moléculaires, UMR 5255 CNRS, 33405
Talence, France
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Abstract
Cognac Wine Distillate (WD), especially during their aging, are marked by complex and
elegant aroma. This work aimed at expanding the knowledge on the Cognac WD aroma by a
sensory-guided approach, involving fractional distillation technique and gas chromatography
coupled to olfactometry and mass spectrometry (GC-O-MS). In doing so, a fruity odorous zone
was highlighted in WD extracts which 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 (v/v 60/40). 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 3 337 µg/L). Given that, diethyl acetals result from the reaction
between ethanol and aldehydes, quantitative correlations between diethyl acetals and
corresponding aldehydes were considered.
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Keywords :
Aroma, Cognac spirit, diethyl acetals, sensory impact
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Introduction
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Cognac spirits are traditional products from the Nouvelle Aquitaine region (France) elaborated
in a context of denomination of appellation origin (AOC Cognac). They originate initially from
fermented grape juices mainly from Vitis Vinifera Ugni blanc (i.e. Trebbiano bianco). This
grape variety produces wines with a low ABV content (Alcohol By Volume less than 10% vol.)
and a high level of acidity. In the Cognac process, before march 31th, the wines should be
distilled through a traditional double distillation in a copper still known as Methode
Charentaise. Young WD at 70% ABV are obtained and placed in oak barrels for sometimes a
very long aging period (several decades). At the end, depending on the Cognac quality, the
cellar master proceeds to blend several WD from different vintages in order to create the final
Cognac spirit.1
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During the aging process, the young WD, usually marked by a component of fermentative
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aromas, is enriched by the wood components, including odorous and taste compounds. WD
is the place of multiple chemical reactions (oxidation, hydrolysis, esterification, rearrangement,
etc) which induce changes in its composition of volatile compounds throughout aging.4–6 The
process of ethanol and water evaporation leads to an increase of volatile compounds
concentration. These phenomenon help to limit the hotness sensation, as well as heavy aromatic
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notes with green character. Also, the aging phenomenon contributes to enhancing particular
aromatic notes (wood, vanilla, dried and fresh fruits, balsamic, spicy) depending on the age of
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the WD , grouped under the term “rancio charentais” . After this long process, WD present a
great complexity and finesse of their aromatic components, complemented by a strong harmony
of taste and flavor which is emphasized in the old commercial Cognac spirits by the blend of
numerous WD.
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The complexity of Cognac spirit aromas related to the presence of a wide diversity of volatile
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odorous compounds associated with production and aging process. Nowadays, nearly 500 of
them from different chemical families have been identified, including alcohols, acids, esters,
ethers, aldehydes, ketones, hydrocarbons, terpenes, C13-norisoprenoids, lactones, phenols,
sulfur and nitrogen compounds.10–18 Many of these compounds have been identified and
assayed in freshly distilled wine spirit. During aging, the balance between these molecules is
much modified.6,19
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Consequently, the complexity of Cognac matrix, makes analyze of odorous compounds,
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particularly the more odor-active, very difficult. Various sample preparation methods can be
considered to make this matrix less complex with dedicated analytical strategies, such as
selective extraction of odorous compounds of interest with Solid Phase Extraction (SPE),20,21
fractionation with High Performance Liquid Chromatography (HPLC)22,23 or vacuum
distillation previous to gas chromatography analysis.24,25 Among various approaches, the one
focused on a specific odor is pertinent to identify compounds using GC-Olfactometry (GC-
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O). This strategy has been considered by several authors for the characterization of Cognac
aroma.9,16,27–29 But in such complex matrix, the strategy developed for the characterization of
odorous volatiles should implicate to develop not only one, but several fractionation methods,
each of them associating at each stage analytical/sensorial approach.
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While numerous publications have studied young Cognac WD spirits, the purpose of this work
was to make progress in the identification of odorous volatile compounds present in aged WD
Cognac spirit via a sensory-guided approach. This research first used fractionated distillation
of WD before applying a GC-O/GC-MS analysis. In doing so, the chemical family of diethyl
acetals was highlighted, some of which have already been identified in Cognac,16,28–31 Chinese
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liquors, Tequila, Grappas and other brandies. Their synthesis, their implication in the
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aromas of aged Cognac spirit, and the ways in which they are formed during aging, were also
considered in the present study.
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Material and methods
Chemicals
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Dichloromethane (99%) was supplied by Fisher Scientific (Illkirch, France). Absolute ethanol
(EtOH) (99%), Silica gel and methanol HPLC grade were from Merck (Semoy, France). 4-
Methylpentan-2-ol (98%), 1,1-diethoxybutane (97%), 1,1-diethoxy-2-methylpropane (97%),
1,1,3-triethoxypropane (97%), 2-(diethoxymethyl)furan (97%), 1,1-diethoxypentane (97%),
1,1-diethoxyhexane (97%), undecanal (97%), heptanal (97%), benzenacetaldehyde (95%), 3-
methylbutanal (97%), pentanal (97%), hexanal (98%), anhydrous sodium sulfate (99%),
Supelclean™ LC-18 SPE tube, O-(2,3,4,5,6-Pentafluorobenzyl)hydroxylamine hydrochloride
(PFBHA) (99%), 4-fluorobenzaldehyde (98%), p-toluenesulfonic acid monohydrate (>98.5%),
diethyl ether, pentane (99%) and molecular sieves 3Å were purchased from Sigma-Aldrich
Chemicals (Saint Quentin Fallavier, France). 2,2-Diethoxyethylbenzene (97%) was purchased
from Life Chemical, Canada. 1,1-diethoxy-3-methylbutane (97%) was obtained from Matrix
Scientific (Elgin, USA). Ultrapure water (Milli-Q, resistivity = 18.2 MΩ cm, Millipore, Saint-
Quentin-en-Yvelines, France) was used.
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Samples
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All WD samples were provided by E.Rémy Martin & C°. They were not commercial products
but selected WD from different vintages that were not blended or diluted. A WD is the product
of several distillations that have been made during the same vintage. All of these WD were then
raised in oak barrels within the company. Depending on the vintage, ABV vary between 55%
and 69%. The percentage of alcohol is presented in the supporting information (Table S1). The
samples were first selected in-house by an internal expert panel as being representative of
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premium spirits. All the WD were removed from barrels in the same year (2016) so that their
age count stopped at bottling. Ten WD were selected in total (2015, 2006, 2002, 1999, 1998,
1997, 1996, 1983, 1982, 1972). For the quantitative measurement of diethyl acetals and
aldehydes WD of 2009 was used for calibration.
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Preparation of Extracts by sequential vacuum distillation
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Two WD (2006 and 1997) were used at beginning for this experiment. One hundred milliliters
of each WD and 400 mL of water, to obtain an ABV of around 14%, were placed in the flask
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of a rotary evaporator steeped in a bath at room temperature. Under vacuum volatiles were
trapped with a condenser equipped with a cooling system (-5°C). The following sequential
distillation parameters were used: 50 mbar for 15 min which permitted to collect fraction F1,
then 30 mbar for 15 min (collection of fraction F2), and 20 mbar for 15 min (fraction F3). At
the end, the distilled volumes obtained corresponded to 10 mL for F1, 25 mL for F2 and 40 mL
for F3. Each fraction collected presented a high level of ethanol (F1 ≈ 65%, F2 ≈ 40%, F3 ≈
20% (v/v)), and they were diluted with ultrapure water to reach 12% EtOH (v/v). After this, the
three fractions obtained were subjected to sensory evaluation by a panel of five experts who
were asked to describe the main olfactory notes of the distillates. The fraction(s) selected by
the sensory panel were then extracted twice by dichloromethane (magnetic stirring: 10 min each
time; 750 rpm). Then the organic phases were combined, dried on anhydrous sodium sulfate
and concentrated to 0.25 mL under nitrogen flow close to 100 mL/min at room temperature
before GC analysis.
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Quantitation of ethyl esters
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Ethyl acetate, ethyl butyrate, ethyl caproate (ethyl hexanoate), ethyl caprylate (ethyl octanoate),
ethyl caprate (ethyl decanoate), ethyl lactate and ethyl laurate (ethyl dodecanoate) (total of ethyl
ester) were quantified using direct injection of the distillate by GC-FID. Initially, ten milliliters
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of each WD were supplemented with 100 µL of internal standard (4-methylpentan-2-ol at 30
g/L in ethanol). Then, one microliter of each sample was directly injected in split mode (1/30).
The capillary column used was a CP WAX 57 CB (Agilent Technologies, Santa Clara, CA,
USA) (50 m length; 0.32 mm internal diameter (i.d.); 0.20 µm film thickness). The injector was
at 260 °C and the flow was constant (1.6 mL/min). The oven was programmed as follows: 35
°C for 6.5 min, then increasing by 5 °C/min to 190 °C and maintained at this temperature for
18 min. The FID detector was maintained at 300 °C.
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Gas chromatography coupled with olfactometry and mass spectrometry analysis (GC-O-
MS)
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GC-O-MS analysis was carried out on an Agilent 7890 B LTM (Low Thermal Mass) (Agilent
Technologies, Santa Clara, CA, USA) gas chromatograph coupled to an olfactometric port
(ODP-3 (Gerstel, Germany). Two microliters of the concentrated organic extract were injected
using a splitless injector (240 °C; splitless time 1 min; purge flow 50 mL/min). Separation was
achieved on a DB-WAX (30 m length; 0.25 mm i.d.; 0.25 µm film thickness). Helium N55 was
used as a carrier gas at a constant flow of 1.5 mL/min. The initial GC oven temperature was set
at 45 °C for 1 min, before rising to 230 °C at 5 °C/min, and was maintained at 230 °C for 15
min. A two-way splitter (Agilent Technologies, Santa Clara, CA, USA) at the column exit
permitted to transfer 50% of the effluent to a MS 5977 A (Agilent Technologies, Santa Clara,
CA, USA) mass spectrometer (transfer line at 250 °C, ion source at 250 °C, electron impact
(EI) voltage at 70 eV, ions acquisition within a range of m/z 40-250), while 50% of the effluent
was constantly directed through a deactivated fused silica column to a sniffing port. Olfactory
data collecting during the GC-O analysis were processed with the Olfactory Recorder Software
Dragon (Nuance Communications, Newton, MA, USA). During a GC-O analysis, the operator
started 7 min after the beginning of the GC run and continued up to 40 min. Odorous zone
descriptors and their durations were monitored by recording the voice of the operator doing
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sniffing as a start and stop signal. For each extract, GC-O analysis was done by three experts.
Instrument setting, data acquisition and processing were controlled by ChemStation (B.04.01)
software. Chemical identification was obtained with the help of the NIST 2004 library (U.S.
National Institute of Standards and Technology, Gaithersburg, MD, USA). Then, each volatile
identification was confirmed by injection of pure standard in the same chromatographic
conditions.
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Synthesis of 1,1-diethoxyheptane, 1,1-diethoxyundecane and 1,1-diethoxy-2-
methylbutane
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A solution of p-toluenesulfonic acid monohydrate (1.90 g, 10 mmol), the corresponding
aldehyde (50 mmol), and molecular sieves 3Å (6.5 g) in anhydrous ethanol (50 mL) was placed
under argon and under gentle oscillating stirring for 18 h. After this, the reaction mixture was
filtered to remove the molecular sieves and then carefully evaporated at 40 °C under reduced
pressure at 150 mbar to remove the ethanol. The crude was diluted with diethyl ether and
filtered again. The organic phase was concentrated at 30 °C under reduced pressure at 600 mbar,
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yielding make the crude product as a colorless oil. The H NMR analysis of crude product
showed that at least 75% of the aldehyde was converted to the corresponding acetal. The residue
was then purified by silica gel column chromatography using diethyl ether and pentane as an
eluent in a volume ratio of 2:98.
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NMR: Nuclear Magnetic Resonance Spectroscopy (NMR): H, and C NMR spectra were
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recorded on a Bruker Avance I ( H: 300 MHz, C: 75 MHz), and the spectra referenced using
the lock frequency of deuterated solvent. Chemical shifts () and coupling constants (J) are
expressed in ppm and Hz, respectively. Merck silica gel 60 (70–230 mesh and 0.063–0.200
mm) was used for flash chromatography. Spots were revealed with potassium permanganate
stain.
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1,1-diethoxyheptane: colorless liquid (75% conversion, 64% isolated yield). H NMR (300
MHz, CDCl ): δ 0.85 (t, J = 6.9 Hz, 3H, CH -7), 1.18 (t, J = 7.1 Hz, 6H, OCH CH ), 1.38 –
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1.22 (m, 8H, CH -3-6), 1.65 – 1.50 (m, 2H, CH -2), 3.47 (dq, J = 9.4, 7.1 Hz, 2H, OCH CH ),
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3.62 (dq, J = 9.4, 7.1 Hz, 2H, OCH CH ), 4.46 (t, J = 5.8 Hz, 1H, CH). C NMR (75 MHz,
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CDCl ) δ 13.97 (C-7), 15.26 (OCH CH ), 22.51 (C-6), 24.65 (C-3), 29.09(C-4), 31.72 (C-5),
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33.56 (C-2), 60.76 (OCH CH ), 102.92 (C-1). The NMR data correspond to those already
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reported in the literature.36
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1,1-diethoxyundecane: colorless liquid (85% conversion, 78% isolated yield). H NMR (300
MHz, CDCl ): δ 0.87 (t, J = 6.9 Hz, 3H, CH -11), 1.20 (t, J = 7.1 Hz, 6H, OCH CH ), 1.38 –
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1.23 (m, 16H, CH -3-10), 1.68 – 1.54 (m, 2H, CH -2), 3.48 (dq, J = 9.4, 7.1 Hz, 2H, OCH CH ),
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3.63 (dq, J = 9.4, 7.1 Hz, 2H, OCH CH ), 4.47 (t, J = 5.8 Hz, 1H, CH). C NMR (75 MHz,
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CDCl ) δ 14.11 (C-11), 15.36 (OCH CH ), 22.69 (C-10), 24.77 (C-3), 29.33, 29.50, 29.55,
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29.58, 29.61 (from C-4 to C-8), 31.91 (C-9), 33.61 (C-2), 60.80 (OCH CH ), 102.98 (C-1).
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1,1-diethoxy-2-methylbutane: colorless liquid (32% isolated yield of 95% purity due to high
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volatility and instability). H NMR (300 MHz, CDCl ): δ 0.87 (t, J = 7.4 Hz, 3H, CH -4), 0.88
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(d, J = 6.8 Hz, 3H, CHCH ), 1.02-1.16 (m, 1H, CH -3a), 1.17 (t, J = 7.1 Hz, 6H, OCH CH ),
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1.18 (t, J = 7.1 Hz, 6H, OCH CH ), 1.47-1.71 (m, 2H, CH -3b, CH -2), 3.70 – 3.56 (m, 2H,
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OCH CH ), 3.53 – 3.40 (m, 2H, OCH CH ), 4.15 (d, J = 6.4 Hz, 1H, CH-1). 13C NMR (75
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MHz, CDCl ) δ 11.32 (C-4), 13.91 (CHCH ), 15.29 (OCH CH ), 24.56 (C-3), 37.90 (C-2),
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61.82, 61.97 (OCH CH ), 106.73 (C-1).
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GC on-column analysis
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Manual injection of the organic extracts of diethyl acetal standards which has been done by
splitless injection at 240 °C on GC Thermo trace GC ultra (Thermo Electron SAS, Courtabœuf,
France) with Flame Ionisation Detection (FID) was repeated on the same chromatograph by
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on-column injection at (30 °C) using a fused-silica needle (10 µL, SGE, Australia). The analysis
was carried out on a capillary BP20 (30 m x 1 µm x 0.53 mm). The ramp GC oven temperature
was set at 45 °C for 1 min, before rising to 230 °C at 5 °C/min, and was maintained at 230 °C
for 15 min. Detection was carried out by Flame Ionization (FID, Thermo).
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Quantitation of diethyl acetals in WD by GC-MS
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SPE Procedure. Extraction of diethyl acetals in WD was performed through solid-phase
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extraction (SPE) with a Supelclean LC-18 cartridge (500 mg) using a robot GX-27X Large-
Volume SPE (Gilson, USA). The cartridge was first conditioned with 7 mL of methanol, then
3 mL of a solution of EtOH/H O (90/10; v/v). Twenty-five milliliters of samples (10 mL of
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WD supplemented by 15 mL of ultrapure water) were spiked with dodecanol (100 µL of a
solution at 10mg/L) as an internal standard (IS) and poured through the cartridge. The solid
phase was rinsed with 9 mL of ultrapure water and dried with pulsed air. The elution was
performed with 5 mL of dichloromethane. The eluate was dried with anhydrous sodium sulfate,
and the supernatant was transferred to a concentration tube to be concentrated to 250 µL under
nitrogen stream.
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GC-MS analysis. Two milliliters of the concentrated organic extract were injected, each time
in triplicate, into a GC system (GC 6890N, Agilent Technologies, Santa Clara, USA) using
splitless mode and separated on a BP20 capillary (50 m length; 0.25 mm i.d.; 0.22 µm film
thickness, SGE, USA). Ion detection was done in Selected Ion Monitoring (SIM) mode on an
Agilent 5973N mass spectrometer (Agilent Technologies, Santa Clara, USA). The initial GC
oven temperature was set at 45 °C for 1 min, before rising to 230 °C at 5 °C/min, and was
maintained at 230 °C for 15 min. A stock solution in ethanol at 1 mg/L was prepared for each
standard. The reference WD (2009 vintage) was supplemented with concentrations ranging
from 2 to 32 µg/L for 1,1-diethoxybutane, 1,1-diethoxyheptane and 1,1-diethoxyundecane; 4 to
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64 µg/L for 1,1-diethoxypentane; 10 to 160 µg/L for 1,1-diethoxyhexane and 2,2-
diethoxyethylbenzene; 200 to 3200 µg/L for 1,1-diethoxy-3-methylbutane. The ratio between
the peak area of each targeted analyte and the peak of the IS was plotted against the spiked
concentration.
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Method Validation. Repeatability assays were carried out with the same WD (2009 vintage)
spiked at the lowest and the highest concentration of calibration for each diethyl acetal then
extracted and analyzed 3 times. Reproducibility assays were also carried out at 2-day intervals
for 17 days. Limit of quantitation (LOQ = 10S/N) and limit of detection (LOD = 3S/N) were
also determined for each diethyl acetal.
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Quantitation of aldehydes (SPME-GC/MS)
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Concentrations of the corresponding aldehydes were measured by solid-phase micro-extraction
coupled to gas chromatography and mass spectrometry (SPME-GC-MS) using a method
adapted from López-Vázquez et al.37
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SPME. A Combi PAL sampler (CTC Analytics, Zwigen, Switzerland) and an Agilent 6890N
gas chromatograph (Agilent, Palo Alto, CA, USA), coupled to an Agilent HP 5973N mass
spectrometer (EI mode at 70 eV) was used. Three milliliters of WD were put in a 20 mL
headspace amber vial and diluted with 7 mL of deionized water. Twenty microliters of IS
solution of 4-fluorobenzaldehyde at 1 mg/L and 200 µL of a solution of PFBHA at 50 g/L were
put into the vial before closure with a PTFE-faced silicone septum/aluminum crimp cap and
homogenized manually. A 1 cm, 50/30 µm divinylbenzene-polydimethylsiloxane (DVB-
PDMS) SPME fiber purchased from Supelco Inc. (Bellefonte, PA, USA) was used. The sample
was preincubated for 5 min at 60 °C. Adsorption lasted 30 min, at the same temperature, with
stirring at 500 r.p.m. (3 sec on and 2 sec off). Then, desorption took place in the injector in
splitless mode for 5 min at 240 °C. The fiber was reconditioned for 10 min at 250 °C.
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GC-MS analysis. The carrier gas was helium N60 (Air Liquide) with a flow rate of 1 mL/min.
A BPX5 column was used (50 m; 0.25 mm, 0.22 µm) (SGE, Ringwood, Australia).
Temperatures were programmed as follows: 50 °C for 5 min, increasing by 3 °C/min to 240 °C
with an isotherm at the final temperature for 15 min. The mass spectrometer, operating in EI
mode (70 eV), was connected to the GC with a heated transfer line at 230
°C. The compounds were quantified using the SIM method on MSD ChemStation software
(B.03.01) from Agilent. The selected ion for IS (4-fluorobenzaldehyde) was m/z 319. For the
3-methylbutyraldehyde, hexanal, heptanal, valeraldehyde and undecanal the quantifier and
qualifier ion was m/z 239, and it was m/z 297 for phenylacetaldehyde.
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Method validation. The linearity of the method was determined by analysis of WD (2009
vintage) sample extract spiked with five increasing concentration levels of the abovementioned
aldehydes. Repeatability was estimated by 5 injections of the lowest and the highest
concentrations of the ranges for each aldehyde. Reproducibility assays were carried out on
spiked WD (2009 vintage), at 2-day intervals for 17 days.
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Determination of olfactory detection thresholds
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Sensory analyses took place in a temperature-controlled room (ISO 8589:2007) maintained at
20 ± 1 °C, equipped with individual boxes. The olfactory detection threshold corresponds to
the lowest concentration perceived by 50% of tasters. Olfactory thresholds of the diethyl acetals
were determined by presenting a three-alternative forced choice (3-AFC) in a Water / Ethanol
60/40 (v/v) matrix (ISO 13301:2002). A panel of 23 experienced tasters was considered.
Among three glasses, one contained a supplemented sample with stepwise increasing
concentrations (factor 2) of the compound to be evaluated. The concentration/response function
is a psychometric function and fits a sigmoid curve [y = 1/(1 + e(-λx))]. Detection probability
was corrected by using the chance factor (P = (3p - 1)/2, where p = the proportion of correct
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responses for each concentration and P = the proportion corrected by the chance effect, 1/3 for
3-AFC). Sigma Plot 8 (SYSTAT) software was used for graphic resolution and nonlinear
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regression by ANOVA transform (SYSTAT, San Jose, CA, USA) .
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Sensory profiling
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The individual diethyl acetals were submitted for sensory evaluation by a panel of 25 experts
with previous experience in sensory analysis of spirits. The panelists were asked to provide
descriptors in the context of an orthonasal perception. The odorant attributes cited were
collected and their occurrence frequencies were calculated by using the ratio number of
occurrences of descriptor/total number of descriptors (ISO 11035:1994).
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Statistical analysis
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Statistical calculations were performed using R i386 3.1.3 version (R Core Team (2016), R: a
language and environment for statistical computing; R Foundation for Statistical Computing,
Vienna, Austria; URL https://www.R-project.org)
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71 Results and discussion
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Evidence for fruity odorous zone determined by GC-O in Cognac spirits distillates and
identification of the related compounds.
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Olfactory test of Cognac WD extracts. Cognac spirit is known to be a very complex matrix
comprising a wide diversity of volatile odorous compounds. In order to achieve progress in the
characterization of volatile compounds associated with fruity odors, two Cognac WD (1997
and 2006) were subjected to a fractionation by vacuum distillation. These two WD were chosen
because they were far enough in age to have organoleptic differences, their volume in stock
being quite substantial and the experts having selected them for their organoleptic qualities
corresponding to their age. In doing so, three fractions were obtained per WD. Then five experts
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were asked to freely describe the odor nuances detected of each fraction of the two WD. All the
fractions presented fruity notes but the F3, particularly from 1997 WD presented soapy and
complex notes. The experts recognized the aromatic nuances of F3 of 1997 WD as being
representative of a high-quality Cognac. Moreover, the total quantity of ethyl esters (ethyl
acetate, ethyl butyrate, ethyl caprate, ethyl caproate, ethyl caprylate, ethyl lactate and ethyl
laurate) in F3 from 1997 WD (8 mg/L) was very low in comparison to that determined in F1
and F2, 702 mg/L and 71 mg/L respectively. It could thus be considered that the fruity notes
described in F3 were not entirely due to the presence of ethyl esters. That is why fraction F3
was selected and subjected to a liquid/liquid extraction prior to GC-O analysis.
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GC-O of F3. An inductive approach using GC-O was adopted. Organic extracts of F3 distillate
fractions from the WD 1997 were subjected to GC-O by single-dimension chromatography.
Fruity odorous zones were detected and their linear retention indices (LRI) were established
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according to the Van den Dool and Kratz equation (aromagram in supporting information;
Table S2). One odorous zone was particularly emphasized as it presented peach notes, at LRI
of 1065 on DB-WAX and 958 on BPX5 column. The mass spectrum matched with that of the
1,1-diethoxy-3-methylbutane in the mass spectral database (NIST, 2004). This compound was
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previously identified in Cognac but without mention of its olfactory descriptors. We took the
opportunity presented by the interesting nuances related to this compound to search for other
representatives of the diethyl acetal family. Next, considering the olfactory properties of this
diethyl acetal, the presence of compounds belonging to the same family was investigated
directly in the WD 1997 extracts. The ion m/z 103 is characteristic of the diethyl acetals family,
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corresponding to the fragment C H O . This ion was targeted in the GC-MS chromatograms.
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Screening of the GC-MS chromatograms led to the emergence of eleven peaks which
corresponded to other diethyl acetals (figure 1). Then, before studying their organoleptic
impact, the pure standards of diethyl acetals were both injected in splitless and on-column mode
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under the same chromatographic conditions. These molecules are possibly thermosensitive.
Indeed, the diethyl acetals could have turned into aldehyde in the high temperature of a splitless
injector for the analysis of the eleven diethyl acetals. The abundance of all the peaks remained
the same for both modes of injection (chromatogram in supporting information Figure S1). This
indicated that the molecules were not degraded during chromatographic analysis and did not
undergo any effect of heat during their injection.
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Validation of the presence of diethyl acetals in Cognac. To confirm these molecules were
present in various Cognac, pure standards were injected by GC-MS. 1,1-Diethoxyheptane, 1,1-
diethoxyhexane, and 1,1-diehtoxy-2-methybutane had to be synthesized, whereas 1,1-
diethoxybutane,
1,1,3-triethoxypropane,
2-(diethoxymethyl)furan,
1,1-diethoxy-2-
methylpropane, 1,1-diethoxyundecane, 1,1-diethoxy-3-methylbutane, 1,1-diethoxypentane and
2,2-diethoxyethylbenzene were commercially available. After injection and co-injection the
presence of these eleven diethyl acetals was validated.
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Quantitation of diethyl acetals in wine distillate of Cognac
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Standard addition of pure compounds in the WD 2009 of Cognac prior to extraction by SPE
allowed us to determine the quantitation slopes for each compound investigated (table 1).
Regarding the validation method, the LOQ and LOD were estimated between 0.06 and 1.15
µg/L and 0.01 and 0.34 µg/L respectively. Repeatability and reproducibility were under 20%.
However, 1,1,3-triethoxypropane, 1,1-diehtoxy-2-methylpropane, 2-(diethoxymethyl)furan
and 1,1-diethoxy-2-mehtylbutane could not be quantified because their repeatability and their
reproducibility were above 20%.
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A GC-MS analysis targeting specific m/z ions was conducted on the extracts (figure 2). In detail,
1,1-diethoxyundecane was more abundant in aged WD (concentration ranges 1 - 10 µg/L).
Conversely, 1,1-diethoxybutane (< LOQ - 18 µg/L), 1,1-diethoxy-3-methylbutane (461 - 3337
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µg/L), 2,2-diethoxyethylbenzene (0 µg/L - 53 µg/L) and 1,1-diethoxypentane (27 µg/L -108
µg/L) have a tendency to be present in lower concentrations in relation to the age of the WD.
1,1-diethoxyhexane and 1,1-diethoxyheptane respectively have concentration ranges from 48
to 159 µg/L and from 5 to 13 µg/L respectively, and seem to be unrelated to the age of the WD.
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The quantity of these compounds was different from that reported in the literature except for
the 2,2-diethoxyethylbenzene (table 2). These differences could be explained by the fact that
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the Cognacs studied by Schreier were end products corresponding to blends of WD from
different vintages. Vinification, fermentation, distillation and maturation modalities could also
be very different and all of these factors have an impact on the concentrations of diethyl acetals.
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Olfactory detection threshold of diethyl acetals, descriptors and sensory impact
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Detection threshold. To assess the role of these compounds on aroma, their detection thresholds
were estimated in the EtOH 40% matrix (table 3). All the diethyl acetals presented a detection
threshold higher than the ranges of concentrations determined in spirits, except 1,1-diethoxy-
3-methylbutane. This compound was the most represented diethyl acetal with concentrations
from 461 µg/L to 3337 µg/L over its olfactory threshold which is at 323 µg/L. Thus, the
content/threshold ratio defining the odor activity value (OAV) index was higher than 1 and we
postulated that this molecule had an impact on the aroma of Cognac WD.
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Organoleptic impact of a mix of diethyl acetals. A mixture of all these compounds prepared at
average concentrations in the WD of Cognac was subjected to an olfactory differentiation
through an orthanasal triangular test. The aim was to find out if an olfactory difference was
perceivable between a mix of H O/EtOH (v:v 60:40) and that with the added diethyl acetals.
2
Out of 25 judges, 23 found an olfactory difference, the test was significant with a p-value of
less than 0.05 and the olfactory impact of diethyl acetals mix being validated. Next, a sensory
profile was carried out with a panel of 25 experts who were not informed of the aim of the
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study, i.e. to describe the olfactory descriptors of each molecule in matrix H O/EtOH 40% at
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double their detection threshold concentration. A total of 21 descriptors were collected for all
the molecules, gathered in main categories and listed according to the number of citations
(results presented in supporting information Table S3). Only the descriptors with occurrence
frequencies > 15% were retained (table 3). Even though these molecules belong to the same
chemistry family, their odor perception was different. Two main olfactory notes were
highlighted: fruity and green. 1,1-diethoxybutane, 1,1-diethoxy-3-methylbutane, 1,1-
diethoxypentane and 1,1-diethoxyheptane were mainly described as having fruity notes but they
had nuances of alcohol, vanilla, floral and green respectively. 1,1-diethoxyhexane, 2,2-
diethoxybenzene and 1,1-diethoxyundecane had green notes with earthy, fruity and spicy
nuances respectively.
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Aldehydes, and the potential origin of the diethyl acetals in Cognac spirit
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Diethyl acetals derive from the reaction between the corresponding aldehydes and ethanol,
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probably during the distillation process and/or aging as an chemical equilibrium.
So, the
aldehydes corresponding to the diethyl acetals under study were quantified. Indeed, isobutanal
has been described as having green and slightly unpleasant aromatic notes and correlations have
been cited of its decrease during aging and formation of the corresponding diethyl acetal.45
Thus, we could postulate that if their quantity were lower, then these aromas might disappear
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and make the WD more pleasant. The quantitation method for aldehydes was validated with
a repeatability and a reproducibility inferior to 20% for all of them (table 4). Several trends
were observed concerning the aldehyde concentrations in relation with WD age (figure 3).
Benzenacetaldehyde concentrations are lower in WD in relation with aging. This could be
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probably due to its evaporation or acetalization reactions. For other aldehydes, differences
were observed depending on WD but without correlation with age. Presumably, enological
parameters could be taken into account in these fluctuations. These differences could originate
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from different levels of oxidation mechanisms and Strecker degradation. Nevertheless, no
clear correlation could be observed between aldehyde concentrations profiles in WD and age
or concentrations of corresponding diethyl acetals.
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In conclusion, the fractionation of WD of Cognac by sequential vacuum distillation analyzed
by GC-O-MS, evidenced a fruity odorous belonging to diethyl acetal family. Eleven diethyl
acetals were detected in WD by GC-MS analysis as 1,1,3-triethoxypropane; 1,1-diethoxy-2-
methylpropane; 2(diethoxymethyl)furan; 1,1-diethoxy-2-methylbutane; 1,1-diethoxy-3-
methylbutane; 1,1-diethoxybutane; 1,1-diethoxypentane; 1,1-diethoxyheptane; 1,1-
diethoxyhexane; 2,2-diethoxyethylbenzene and 1,1-diethoxyundecane. Seven of these
compounds were quantified by GC-MS. To clarify their sensorial impact in Cognac WD, their
detection thresholds were established thanks to a 3-AFC method. After all, only 1,1-diethoxy-
3-methylbutane had an olfactory impact in WD. Diethyl acetals being the results of chemical
reactions between corresponding aldehydes and ethanol, concentrations of aldehydes were
determined with GC-MS in various WD but without significant correlations. More efforts will
be aimed at the monitoring of the kinetics of concentration of diethyl acetals and aldehydes in
the same WD during aging.
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95 Acknowledgements
96
We thank Dr. Sophie Tempère for her support in sensory analysis.
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97 Supporting information
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Table S1: Alcohol by volume (%) of the WD
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Table S2: Aromagram of F3 1997 on DB-WAX. Linear retention index (LRI) established
according to the Van den Dool and Kratz equation.
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Figure S1: Overlay of chromatogram obtained with GC-FID in split-splitless injection mode
(regular line) and in on-column injection mode (dotted line) for pure standards of diethyl
acetals.
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Table S3: Descriptors and occurrence frequencies of diethyl acetals.
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Figure S2: Spearman test for correlations between concentrations in diethyl acetals and
concentrations of aldehydes. The age of WD are put in each graphic.
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07 References
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4
4
4
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11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
(1)
(2)
(3)
Cantagrel, R.; Lurton, L.; Vidal, J. P.; Galy, B. From Vine to Cognac. In Fermented beverage
production; Lea A.G.H., Piggott J.R. Springer: Boston, MA, 1995; pp 208–228.
Singleton, L. Maturation of Wines and Spirits: Comparisons, Facts, and Hypotheses. Am. J.
Enol. Vitic. 1995, 46 (1), 98–115.
Fiches, G.; Saint Eve, A.; Jourdren, S.; Déléris, I.; Brunerie, P.; Souchon, I. Temporality of
Perception during the Consumption of French Grape Brandies with Different Aging Times in
Relation with Aroma Compound Release: Perception and Aroma Compound Releases during
Brandy Consumption. Flavour Fragr. J. 2016, 31 (1), 31–40.
Marche, M.; Joseph, E.; Groizet, A.; Audebert, J. Etude Théorique Sur Le Cognac, Sa
Composition et Son Vieillissement Naturel En Fûts de Chêne. Rev Fr. Oenol 1975, 57, 1–106.
Onishi, M.; Guymon, J. F.; Crowell, E. A. Changes in Some Volatile Constituents of Brandy
during Aging. Am. J. Enol. Vitic. 1977, 28, 152–158.
Watts, V. A.; Butzke, C. E.; Boulton, R. B. Study of Aged Cognac Using Solid-Phase
Microextraction and Partial Least-Squares Regression. J. Agric. Food Chem. 2003, 51 (26),
7738–7742.
Guymon, J. F. Influence of Warehouse Temperatures on the Aging of California Brandy. Wines
Vines 1973, 36–38.
Léauté, R.; Mosedale, J. R.; Mourgues, J.; Puech, J. L. Barrique et Vieillissement Des Eaux-de-
Vie. In Oenologie fondements scientifiques et technologiques; Flanzy, C.; Tec&Doc: Paris,
France, 1998; pp 1085–1142.
Ferrari, G.; Lablanquie, O.; Cantagrel, R.; Ledauphin, J.; Payot, T.; Fournier, N.; Guichard, E.
Determination of Key Odorant Compounds in Freshly Distilled Cognac Using GC-O, GC-MS, and
Sensory Evaluation. J. Agric. Food Chem. 2004, 52 (18), 5670–5676.
(4)
(5)
(6)
(7)
(8)
(9)
(10) Schaefer, J.; Timmer, R. Flavor Components in Cognac. J Food Sci 1970, 35 (1), 10–12.
(11) Caumeil, M. Le Cognac. Pour la Science. 1983, No. 74, 48–56.
(12) De Rijke, D.; Ter Heide, R. Flavour Compounds in Rum, Cognac and Whisky. In Flavour distilled
beverage, origin and development; Piggott J.R. Ellis Horwood: Chichester, UK, 1983; pp 192–
202.
(13) Lurton, L.; Mazerolles, G.; Galy, B.; Cantagrel, R.; Vidal, J. P. Influence de La Technologie de
Vinification Sur La Qualité Des Eaux-de-Vie de Cognac, Exemple Des Norisoprenoides et Des
Alcools Supérieurs. In 1er Symposium internationalꢀ: Les eaux-de-vie traditionnelles d’origine
viticole; Bertrand, A. Tec&Doc: Paris, France, 1990; pp 127–136.
(14) Lurton, L.; Ferrari, G.; Snakkers, G. Cognac: Production and Aromatic Characteristics. In
Alcoholic Beverages; Piggott J.R.: New York, NY, 2012; pp 242–266.
(15) Slaghenaufi, D.; Perello, M.-C.; Marchand, S.; de Revel, G. Quantification of
Megastigmatrienone, a Potential Contributor to Tobacco Aroma in Spirits. Food Chem. 2016,
203, 41–48.
(16) Ledauphin, J.; Le Milbeau, C.; Barillier, D.; Hennequin, D. Differences in the Volatile
Compositions of French Labeled Brandies (Armagnac, Calvados, Cognac, and Mirabelle) Using
GC-MS and PLS-DA. J. Agric. Food Chem. 2010, 58 (13), 7782–7793.
(17) Uselmann, V.; Schieberle, P. Decoding the Combinatorial Aroma Code of a Commercial Cognac
by Application of the Sensomics Concept and First Insights into Differences from a German
Brandy. J. Agric. Food Chem. 2015, 63 (7), 1948–1956.
(18) Malfondet, N.; Gourrat, K.; Brunerie, P.; Le Quéré, J.-L. Aroma Characterization of Freshly-
Distilled French Brandies; Their Specificity and Variability within a Limited Geographic Area:
Aroma Characterization of Freshly-Distilled French Brandies. Flavour Fragr. J. 2016, 31 (5),
361–376.
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4
4
4
4
4
4
4
4
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4
4
4
4
4
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4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
00
01
02
03
04
05
06
(19) Puech, J. L.; Léauté, R.; Clot, G.; Nomdedeu, L.; Mondiés, H. Evolution de Divers Constituants
Volatils et Phénoliques Des Eaux-de-Vie de Cognac Au Cours de Leur Vieillissement. Sci
Aliments 1984, 4, 65–80.
(20) Culleré, L.; Escudero, A.; Cacho, J.; Ferreira, V. Gas Chromatography−Olfactometry and
Chemical Quantitative Study of the Aroma of Six Premium Quality Spanish Aged Red Wines. J
Agric Food Chem 2004, 52 (6), 1653–1660.
(21) Campo, E.; Cacho, J.; Ferreira, V. Solid Phase Extraction, Multidimensional Gas
Chromatography Mass Spectrometry Determination of Four Novel Aroma Powerful Ethyl
Esters. J. Chromatogr. A 2007, 1140 (1–2), 180–188.
(22) Stamatopoulos, P.; Frérot, E.; Tempère, S.; Pons, A.; Darriet, P. Identification of a New Lactone
Contributing to Overripe Orange Aroma in Bordeaux Dessert Wines via Perceptual Interaction
Phenomena. J Agric Food Chem 2014, 62 (12), 2469–2478.
(23) Ferreira, V.; Hernández-Orte, P.; Escudero, A.; López, R.; Cacho, J. Semipreparative Reversed-
Phase Liquid Chromatographic Fractionation of Aroma Extracts from Wine and Other Alcoholic
Beverages. J. Chromatogr. A 1999, 864 (1), 77–88.
(24) Gros, J.; Lavigne, V.; Thibaud, F.; Gammacurta, M.; Moine, V.; Dubourdieu, D.; Darriet, P.;
Marchal, A. Toward a Molecular Understanding of the Typicality of Chardonnay Wines:
Identification of Powerful Aromatic Compounds Reminiscent of Hazelnut. J Agric Food Chem
2017, 65 (5), 1058–1069.
(25) MacNamara, K.; van Wyk, C. J.; Augustyn, O. P. H.; Rapp, A. Flavour Components of Whiskey. I.
Distribution and Recovery of Compounds by Fractional Vacuum Distillation. South Afr. J. Enol.
Vitic. 2017, 22 (2), 69–74.
(26) Van Ruth, S. M. Methods for Gas Chromatography-Olfactometry: A Review. Biomol. Eng. 2001,
17 (4–5), 121–128.
(27) Leclaire, E.; Cantagrel, R.; Maignial, L.; Snakkers, G.; Ferrari, G. Contribution to
characterisation of young Cognac aroma. OENO One 1999, 33 (3), 133.
(28) Ledauphin, J.; Basset, B.; Cohen, S.; Payot, T.; Barillier, D. Identification of Trace Volatile
Compounds in Freshly Distilled Calvados and Cognac: Carbonyl and Sulphur Compounds. J
Food Compos Anal 2006, 19 (1), 28–40.
(29) Nykänen, L.; Suomalainen, H. Aroma of Beer, Wine and Distilled Alcoholic Beverages; D. Reidel
Publishing Company: Dordrecht, 1983.
(30) Ledauphin, J.; Saint-Clair, J.-F.; Lablanquie, O.; Guichard, H.; Founier, N.; Guichard, E.; Barillier,
D. Identification of Trace Volatile Compounds in Freshly Distilled Calvados and Cognac Using
Preparative Separations Coupled with Gas Chromatography−Mass Spectrometry. J Agric Food
Chem 2004, 52 (16), 5124–5134.
(31) Nykanen, L. Formation and Occurrence of Flavor Compounds in Wine and Distilled Alcoholic
Beverages. Am. J. Enol. Vitic. 1986, 37 (1), 84–96.
(32) Fan, W.; Qian, M. C. Characterization of Aroma Compounds of Chinese “Wuliangye” and
“Jiannanchun” Liquors by Aroma Extract Dilution Analysis. J Agric Food Chem 2006, 54 (7),
2695–2704.
(33) Benn, S. M.; Peppard, T. L. Characterization of Tequila Flavor by Instrumental and Sensory
Analysis. J Agric Food Chem 1996, 44 (2), 557–566.
(34) Masino, F.; Montevecchi, G.; Riponi, C.; Antonelli, A. Composition of Some Commercial
Grappas (Grape Marc Spirit): The Anomalous Presence of 1,1-Diethoxy-3-Methylbutane: A
Case Study. Eur Food Res Technol 2009, 228 (4), 565–569.
(35) Mihajilov-Krstev, T. M.; Denić, M. S.; Zlatković, B. K.; Stankov-Jovanović, V. P.; Mitić, V. D.;
Stojanović, G. S.; Radulović, N. S. Inferring the Origin of Rare Fruit Distillates from
Compositional Data Using Multivariate Statistical Analyses and the Identification of New
Flavour Constituents. J Sci Food Agr 2015, 95 (6), 1217–1235.
(36) Pérez-Mayoral, E.; Martín-Aranda, R. M.; López-Peinado, A. J.; Ballesteros, P.; Zukal, A.; Čejka,
J. Green Synthesis of Acetals/Ketals: Efficient Solvent-Free Process for the Carbonyl/Hydroxyl
Group Protection Catalyzed by SBA-15 Materials. Top. Catal. 2009, 52 (1–2), 148–152.
2
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ACS Paragon Plus Environment

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Page 22 of 31
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5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
07
08
09
10
11
12
13
14
15
16
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19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
(37) López-Vázquez, C.; Orriols, I.; Perelló, M.-C.; de Revel, G. Determination of Aldehydes as
Pentafluorobenzyl Derivatives in Grape Pomace Distillates by HS-SPME-GC/MS. Food Chem.
2012, 130 (4), 1127–1133.
(38) Cometto-Muñiz, J. E.; Abraham, M. H. Human Olfactory Detection of Homologous N-Alcohols
Measured via Concentration-Response Functions. Pharmacol. Biochem. Behav. 2008, 89 (3),
279–291.
(39) Van den Dool, H. A Generalization of the Retention Index System Including Linear
Temperature Programmed Gas-Liquid Partition Chromatography. J Chromatogr A 1963, 11,
463–471.
(40) Ruelle, H. D. L.; Klok, J.; Rinken, M.; Felix, M. Characterization of Acetals by Means of Capillary
Gas Chromatography/Mass Spectrometry. Rapid Commun Mass Sp 1995, 9 (15), 1507–1511.
(41) Schreier, P.; Drawert, F.; Winkler, F. Composition of Neutral Volatile Constituents in Grape
Brandies. J Agric Food Chem 1979, 27 (2), 365–372.
(42) Awad, P.; Athès, V.; Decloux, M. E.; Ferrari, G.; Snakkers, G.; Raguenaud, P.; Giampaoli, P.
Evolution of Volatile Compounds during the Distillation of Cognac Spirit. J Agric Food Chem
2017, 65 (35), 7736–7748.
(43) Madrera, R. R.; Gomis, D. B.; Alonso, J. J. M. Influence of Distillation System, Oak Wood Type,
and Aging Time on Volatile Compounds of Cider Brandy. J Agric Food Chem 2003, 51 (19),
5709–5714.
(44) Vidal, J. P.; Mazerolles, G.; Estreguil, S.; Cantagrel, R. Analyse Quantitative de La Fraction
Carbonylée Volatile Des Eaux-de-Vie de Cognac. In Proceedings of the 1er Symposium
Scientifique International du Cognac, “Elaboration et connaissance des spiritueux”; Cantagrel,
Rꢀ; Tec&Doc: Paris, France, 1993; pp 11–15.
(45) Galy, B.; Loizeau, A.; Giraud, N.; Lurton, L. Mécanismes de formation et conséquences
qualitatives de l’isobutanal présent dans les Eaux-de-vie de Cognac. In 2ème Symposium sur
les eaux-de-vie traditionnelles d’origine viticole; Bertrand, A. Tec&Doc: Paris, France, 2007; pp
111–115.
(46) Escudero, A.; Asensio, E.; Cacho, J.; Ferreira, V. Sensory and Chemical Changes of Young White
Wines Stored under Oxygen. An Assessment of the Role Played by Aldehydes and Some Other
Important Odorants. Food Chem. 2002, 77 (3), 325–331.
(47) Oliveira, C. M.; Ferreira, A. C. S.; De Freitas, V.; Silva, A. M. S. Oxidation Mechanisms Occurring
in Wines. Food Res. Int. 2011, 44 (5), 1115–1126.
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40 Figure Captions
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41
42
Figure 1: Diethyl acetal compounds evidenced in Cognac spirit (identification confirmed by
LRI, MS and standard injection).
5
5
43
44
Figure 2: Concentrations (µg/L) of diethyl acetals (mean ± standard deviation; n=3) in the 10
WD analyzed by GC-MS.
5
5
45
46
Figure 3: Concentrations (µg/L) of aldehydes (mean ± standard deviation; n=3) in the 10 WD
analyzed by SPME-GC-MS.
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Table 1: Validation data of GC-MS method for diethyl acetals analyses. Repeatability (n=3).
Reproducibility (2-day intervals for 17 days). LOD = 3S/N. LOQ = 10S/N.
m/z qualifier
Repeatability
Reproducibility
LODa
(µg/L)
0.02
LOQb
Name
R²
(
quantifier)
103 (101)
103 (115)
103 (115)
103 (129)
103 (143)
(%)
8
(%)
17
17
19
16
14
10
9
(µg/L)
0.08
1.11
0.17
1.15
0.09
0.26
0.06
1
,1-diethoxybutane
0.9964
0.9899
0.9936
0.9974
0.9918
0.9964
0.9957
1
,1-diethoxy-3-methylbutane
14
14
11
10
6
0.33
1
1
,1-diethoxypentane
0.04
1
,1-diethoxyhexane
0.34
,1-diethoxyheptane
0.03
2
,2-diethoxyethylbenzene
103 (121, 149)
103 (199)
0.08
1
,1-diethoxyundecane
18
0.01
a
b
Limit of detection. Limit of quantitation
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Table 2: Comparison of concentrations of diethyl acetals previously cited in the literature and
this study.
Range of diethyl acetals
Range of diethyl acetals
concentrations in Cognac concentrations in Cognac
Name
spirits (cited from
spirits (determined in
this study) (µg/L)
0 – 18
literature) (µg/L)41
1
,1-diethoxybutane
nd
28 – 300
2 – 11
14 - 61
nd
1
,1-diethoxy-3-methylbutane
461 – 3337
27 – 108
1
1
,1-diethoxypentane
1
,1-diethoxyhexane
48 – 159
,1-diethoxyheptane
5 – 13
2
,2-diethoxyethylbenzene
,1-diethoxyundecane
1 – 39
nd
0 – 53
1
1 – 10
nd: not determined
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Table 3: Olfactory detection thresholds and descriptors of the diethyl acetals.
Olfactory detection
Name
Odor descriptorsb
OAVc
threshold (µg/L)a
1
,1-diethoxybutane
616
323
Fruity, alcohol
Fruity, vanilla
Fruity, floral
Green, earthy
Fruity, green
Green, fruity
Green, spicy
<1
>1
<1
<1
<1
<1
<1
1
,1-diethoxy-3-methylbutane
1
1
,1-diethoxypentane
501
1
,1-diethoxyhexane
1995
512
,1-diethoxyheptane
2
,2-diethoxyethylbenzene
741
1
,1-diethoxyundecane
1253
a
b
Determined in a H O/EtOH 60:40 (v:v); Descriptors mainly mentioned by the panel with
2
c
occurrence frequencies > 15%; Odor Activity Value (ratio between the concentration of the
diethyl acetal in WD and its detection threshold)
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Table 4: Validation data of GC-MS method for various aldehydes. Repeatability (n=3).
Reproducibility (2-day intervals for 17 days)
m/z quantifier
Repeatability
Reproducibility
(%)
Name
CAS
after
R²
(%)
derivatization
butanal
-methylbutanal
pentanal
123-72-8
590-86-3
110-62-3
66-25-1
239
239
239
239
239
297
239
0.9740
0.9932
0.9921
0.9925
0.9922
0.9903
0.9961
4
4
4
6
5
2
5
11
10
9
3
hexanal
16
12
7
heptanal
111-71-7
122-78-1
112-44-7
benzeneacetaldehyde
undecanal
14
2
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Figure 1:
O
O
O
O
O
O
O
1
,1-diethoxybutane
1,1-diethoxy-2-methylpropane
1,1,3-triethoxypropane
O
O
O
O
O
O
O
1
,1-diethoxypentane
1,1-diethoxy-3-methylbutane
2-(diethoxymethyl)furan
O
O
O
O
O
O
1
,1-diethoxyheptane
1,1-diethoxy-2-methylbutane
2,2-diethoxyethylbenzene
O
O
O
O
1
,1-diethoxyhexane
1,1-diethoxyundecane
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Figure 2:
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