History [1]

​1st Century AD: Introduction of viticulture in Charentes, establishing the region’s winemaking tradition.
11th Century: Expansion of the salt trade as a major economic driver; Poitou wines gain prominence in North Sea markets, transported via Dutch merchant fleets.
Middle Ages: Cognac emerges as a key wine-trading hub, leveraging its established salt commerce for distribution.
16th Century: Dutch merchants procure wines from Champagne and Borderies vineyards; distillation in the Netherlands produces ‘brandwijn’ (‘burnt wine’), the precursor to brandy.
17th Century: Adoption of double distillation refines production, enhancing stability and transportability of wine spirits.
Mid-19th Century: Shift from cask to bottle shipping drives industrial advancements in glass manufacturing, packaging, and printing.
1875: Phylloxera infestation decimates Cognac vineyards; replanting with American rootstocks facilitates recovery. Establishment of the Station Viticole in 1892 formalizes quality control and research.
Early 20th Century:

• 1909: Official delimitation of Cognac’s geographical production zones.
• 1936: Recognition of Cognac under the Appellation d’Origine Contrôlée (AOC) system, ensuring product authenticity.
• 1938: Refinement of regional appellations, further defining production standards.
• 2020s: Cognac exports reach 96.8% of 166 million bottles. Preferences vary globally—neat or in cocktails (UK), aperitifs (France), trendy among rappers and hipsters (US), and paired with meals (China). Global consumption: 55% VS, 35.8% VSOP, 8.2% XO.

Your browser does not support viewing this document. Click here to download the document.

Cognac Production Specifications

• Production Region 
• Production Techniques: Grapes,  Winemaking, and Distillation 
• Production Techniques: Maturation

<

>

Cognac Production Region

• French Administrative Region: Nouvelle-Aquitaine
• French Departments: Charente and Charente-Maritime
• Climate
  • Winkler Region II with oceanic influence on the coastal regions
  • ​​Droughts are rare due to the region’s proximity to the ocean. Irrigation is not permissible

Crus and Soil Types [1]:

Your browser does not support viewing this document. Click here to download the document.

Influence of Growing Area [4]
In Cognac, the production region is divided into “Crus.”  While studies into the specific differences between crus are limited, as noted below, the Cognac AOC website (cognac.fr) notes that the total Cognac vineyard area is  88,337 hectares (10% of all the French vineyard) [5]. Malfondet et al. (2016) suggested that the distinctive aromas of brandies from different Growing Areas in a limited region are likely a result of complex interactions between common aroma compounds present in different concentrations and not the presence of specific and unique aromatic compounds that vary according to the growth area.  In the study, however, the growing areas were not specified.  Instead, the differences in aromatic compound concentration listed were between A1 and B1, with the key volatile difference being:

• A1 having higher concentrations of ethyl prop-2-enoate, ethyl butanoate, ethyl 2-methyl butanoate, ethyl hexanoate, 3-ethoxypropan-1-ol, (Z)-hex-3-en-1-ol, ethyl octanoate, (Z)-ocimenol, diethyl succinate. Several of these compounds, ethyl esters with low molecular weight and C6-alcohols in particular, are known for being responsible for light, fruity, or green notes.
• B2 has higher concentrations of 2-methylpropan-1-ol, ethyl dodecanoate, benzyl alcohol, ethyl tetradecanoate, ethyl hexadecanoate, and ethyl octadeca-9,12-dienoate. ​

Cognac Production Techniques
As noted in https://www.hawaiibevguide.com/brandy
Grapes

• Main Varieties: Ugni Blanc (Trebbiano) constitutes <98% of the vineyard planting.  Accessory varietals, mainly La Volle Blanche, were commonplace before Phylloxera. However, Ugni Blanc could be grafted onto Phylloxera better than the traditional varieties. 
• Accessory Varieties: Folle Blanche, Colombard, Montilis, Folignan
• Harvest is by machine when grapes have a potential alcohol content of 9% ABV.

Winemaking

• Yeast: Six Saccharomyces cerevisiae strains are permissible, and multiple strains can be employed to create different types of eau de vie. These strains include Lalvin FC9, Fermivin 7013, Fermivin SM102
• No additional sugar or sulfites are allowed in fermentation.
• Distillation and Proofing
  • Still: Copper pots in a process called "Charentais distillation.
  • The “first chauffe” is the initial distillation of wine, resulting in the brouillis, or first distillate.
  • The “second chauffe” (also called “repasse” or “bonne chauffe”) designates the distillation of the brouillis and produces Cognac wine spirit once the beginning and the end of distillation (also called “phlegme”) are eliminated. This results in a distillate of 70-72.4% ABV [1].
  • Heads or tails from the first or second distillation may be added to the wine or brouillis and distilled a second time.
• Dilution after aging is done to bring spirit to proof.
• Cognac may be colored with caramel or boisé. Boisé is made by boiling wood chips in water and then reducing the liquid to intensify the color.​

Behavior of ethanol and aroma compounds during distillation

• Light Compounds
  • Light-I Compounds (L-I): More present in the first liters of the head fractions (>10% in the head of the Brouillis Distillation), with minimal presence in the tails and residues.
  • Light-II Compounds (L-II): Mostly present in the brouillis and heart fractions with a slightly higher presence in the tails than L-I compounds. 
  • Light-III Compounds (L-III): Slightly less present in the heads and slightly more present in the second and tails compared to L-I and L-II compounds.
  • Light-IV Compounds (L-IV): Slightly less present in the heads and slightly more present in the second and tails.
• Intermediate Compounds
  • Intermediate-I (I-I) Compounds: Methanol is the only compound in this group. Because its volatility is very similar to ethanol's, it is found in all fractions.
  • Intermediate-II (I-II) Compounds: Concentration peaks in the heart fraction, with the brouillis distillation typically showing an inverted-V concentration profile.
  • Intermediate-III (I-III) Compounds: Concentration peaks between the heart and second fraction, with the brouillis distillation typically showing an inverted-V concentration profile. 
  • Intermediate-IV (I-IV) Compounds: Concentration peaks near the tail cut, with the brouillis distillation typically showing an inverted-V concentration profile.  Group I-IV can be considered a transition group between intermediate and heavy compounds since its compounds tend to be more concentrated in the later distillation stages, between the second and tail fractions.
• Heavy Compounds
  • Heavy-I (H-I) Compounds: Concentration increases throughout the entire distillation, presenting a concentration peak in the final liters of distillate. 

Aging

• Aging Vessel: Aging starts in new French oak from the Tronçais and Limousin forests. The typical barrel is 350 litres.
• Aging Process: Both new and used casks are used.  Used casks reduce the influence of oak-derived flavors. 
• Age Duration
  • Very Special (VS):  
    • Aged Duration: At least two years
    • Other terms:   “3 Stars ”, “Selection,” and “De Luxe” 
  • Very Superior Old Pale (VSOP): 
    • Age Duration: At least four years
    • Other terms: Reserve”, “Old,” “Rare,” “Royal,” and “Very Superior Old Pale.”
  • Extra Old (XO): 
    • Age Duration: At least ten years
    • Other terms: “Hors d’âge”, “Extra”, “Ancestral”, “Ancêtre”, “Or”, “Gold”, “Impérial”, “Extra Old”
  • XXO (Extra Extra Old): Aged at least 14 years
  • Hors d'âge: Beyond Age

Influence of Aging and “Rancio Charentais” [6]
Rancio Charentais is the aging phenomenon that refers to highly desirable aromas like wood, vanilla, dried and fresh fruits, balsamic, and baking spice that develop after 15-20 years in barrels. While the aromas of unaged and young wine distillates have been studied in depth, those of aged wine distillates have been little explored [7]. The aroma compounds attributes to this include:
Aromatic Compound Contributions: Influenced by oak species, growing location, toast level, cask newness, and maturation duration.
Maturation Effects:

• Fatty acid ethyl esters increase over time.
• Acetate esters of higher alcohols decrease due to ethanol abundance, leading to ethyl ester formation via transesterification.
• Acetic acid rises from oak extraction or ethanol oxidation.

Oxidative Reactions: Convert fatty acids into methyl ketones (e.g., 2-heptanone, 2-nonanone, 2-undecanone, 2-tridecanone).
Distillate-Wood Interactions: Generate new molecules, including esters (ethyl vanillate, ethyl syringate) and ethers (vanillin ethyl ether).

Significant Aroma Compounds

Cognac aroma compounds, especially those in unaged distillate, have been studied.  We highly recommend reading the following comprehensive studies: 

• [9] Zanghelini, G., Giampaoli, P., Athès, V., Vitu, S., Wilhelm, V., & Esteban-Decloux, M. (2024). Charentaise distillation of cognac. Part I: Behavior of aroma compounds. Food Research International, 178, 113977. https://hal.science/hal-04394944/file/2024_Zanghelini%20et%20al._Charentaise%20distillation_part%20I_manuscrit.pdf 
• [10] Ledauphin, J., Le Milbeau, C., Barillier, D., & Hennequin, D. (2010). Differences in the volatile compositions of French labeled brandies (Armagnac, Calvados, Cognac, and Mirabelle) using GC-MS and PLS-DA. Journal of agricultural and food chemistry, 58(13), 7782-7793.
• [11] Yuan, X., Zhou, J., Zhang, B., Shen, C., Yu, L., Gong, C., Xu, Y. and Tang, K., 2023. Identification, quantitation, and organoleptic contributions of furan compounds in brandy. Food Chemistry, 412, p.135543. https://doi.org/10.1016/j.foodchem.2023.135543
• [12] Watts, V. A. (2003). Headspace analysis of aged cognac and California pot -still brandy. ProQuest Dissertations & Theses. https://www.proquest.com/docview/305344264  

• For more on General wine aroma compounds 
  • https://www.hawaiibevguide.com/wine-aroma-compounds-pt-1.html 
  • https://www.hawaiibevguide.com/wine-aroma-compounds-pt-2.html 

• Alcohols, Esters, Aldehydes, Acetals, and Diketones
• Norisoprenoids and Terpenes
• Lactones, Phenols, and Frurans
  

<

>

Alcohol Formation and Concentration Influences

• Grape ripeness at harvest influences the concentration of six-carbon-atom alcohols like hexanol and hexenol. For example, cis-3-hexenol decreases with ripening [1]. 
• Fermentation is the primary formation period of most alcohols.  This occurs by the degradation of sugars, the transamination of amino acids, and the reduction of aldehydes by yeast. For more on the formation of alcohols during winemaking: hawaiibevguide.com/wine-aroma-compounds-pt-2.html#Fusel_Alcohols/Fusel_Oils/Higher_Alcohols  
• Influence of distillation: Essentially unchanged [9]. 

Ester Formation and Concentration Influences

• Winemaking: Esters are typically formed during fermentation. For more on esters created during winemaking: https://www.hawaiibevguide.com/wine-aroma-compounds-pt-2.html#Esters 
• Distillation
  • Increases the concentration of some esters [9]
    • Example of increased esters: Isoamyl dodecanoate, ethyl tetradecanoate, ethyl hexadecanoate, isoamyl decanoate, ethyl linoleate, ethyl oleate, ethyl linolenate, isobutyl decanoate, ethyl dodecanoate, ethyl octadecenoate, methyl salicylate, 2-phenylethyl octanoate and ethyl formate. 
    • Reaction mechanism: These esters can increase due to water and other undesired compound removal by distillation. 
  • Decreases the concentration of esters found in the head fraction (55-69%) [9]
    • Examples of decreased esters: ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl hexanoate, and hexyl acetate.
    • Reaction mechanism: Temperature-catalyzed hydrolysis may cause losses in esters while yielding the corresponding carboxylic acids (in the case of ethyl esters) or higher alcohols (for acetate esters), or from the saponification of the esters with copper ions from the alembic walls. Ester hydrolyses are pH-dependent reactions whose rates are reportedly higher for acetate esters and long-chain ethyl esters. 
  • Lees distillation can increase ester concentration [9]
    • Examples of esters increased by distillation with lees: ethyl octanoate (pineapple, green aroma), ethyl decanoate (pear, floral aroma), ethyl dodecanoate (sweet, floral aroma), isoamyl octanoate (fruity, oily pineapple aroma), isoamyl decanoate (waxy, banana), isoamyl dodecanoate (waxy, fatty, wine aroma), 2-phenylethyl octanoate (waxy, cocoa) and 2-phenylethyl decanoate, ethyl tetradecanoate (sweet, waxy), ethyl 9-decenoate (fruity, fatty)
    • Reaction Mechanism: Long-chain esters tend to be adsorbed on yeast cell walls after fermentation due to a higher lipid solubility.  The heat from distillation can cause some esters to be gradually released from yeast cell walls (lees) during distillation.
  • Aging
    • Fatty acid ethyl esters increase with the time of maturation of Wine distillates [9].
    • Decreases in the acetate esters of certain higher alcohols decreased as a result of the abundance of ethanol compared to other alcohols, which may drive the formation of ethyl esters or displace higher alcohols from their acetate esters to form ethyl acetate (transesterification). 

Aldehyde Formation and Concentration Influences

• Distillation increases the concentration of some aldehydes [9]
  • Examples of increased aldehyde concentration: isobutanal, acetaldehyde and benzaldehyde.
  • Reaction Mechanisms: Strecker aldehydes of isobutanal, acetaldehyde, and benzaldehyde are heat catalyzed and formed from the reactions of α-amino acids with carbonyl compounds, resulting in an aldehyde that is one carbon shorter than its amino acid precursor. As the formation is heat-catalyzed, it is more of a factor during double distillation. Acetaldehyde is reportedly formed from cysteine and alanine, whereas isobutanal derives from valine and glyoxal, and benzaldehyde stems from isoleucine.
• Maturation in oak increases some aldehydes.
  • Examples of increased aldehyde concentration: Benzaldehyde 
  • Reaction Mechanism: Direct contribution of aromatic compounds [13]. 

Acetal Formation and Concentration Influences

• Distillation can form some acetals and hydrolyze others
  • Examples of acetals formed during distillation
    • 1,1-diethoxyethane, the major acetal in distilled spirits, is formed from the reaction of ethanol and acetaldehyde
    • 1,1-diethoxyisobutane likely originates from the acetalization of ethanol and isobutanal (2-methylpropanal) (Thibaud et al., 2019). 
  • Mechanism of reaction [9]
    • Acetal formation is attributed to reversible reactions where aldehydes and alcohols initially form a hemiacetal; then, the hemiacetal condenses with another alcohol. The reaction is favored by the acid environment of the WD and catalyzed by the presence of hydrogen ions (H+) and appears to be particularly significant in directly fired stills. 
    • Decreasing ethanol concentration in the boiler during distillation could also spur the reverse reaction, leading to the hydrolysis of acetals into their corresponding aldehydes.

​​Diketone Formation and Concentration Influences [7]

• Winemaking: Oxidation forms 3‑Methyl-2,4-nonanedione.
• Distillation: 
  • 3‑Methyl-2,4-nonanedione increases in concentration due to the removal of water and other compounds via distillation. 
  • Distillation with yeast further increases 3‑Methyl-2,4-nonanedione, though the mechanism behind this new observation is not yet defined.
• Aging of Cognac showed no significant correlation between 3‑Methyl-2,4-nonanedione and the age of the wine distillates studied.

Norisoprenoids and Terpene Formation and Concentration Influences [15]

• Harvest: β-Damascenone, a significant norisoprenoid (and ketone), increases in concentration with grape ripeness due to carotenoid degradation [1]. Other terpenoids from carotenoid degradation include vitispiranes, a-ionone.
• Winemaking: Initial terpene formation occurs in grapes.
• Distillation: Concentration generally increased
  • Distillation generally concentrates terpenes already existing in the wine by removing water and other compounds. 
  • Acid hydrolysis of ß-D-glucose moieties, catalyzed by the high temperatures and low pH of wine distillation, results in the gradual liberation of odor-active terpenes and norisoprenoids.
  • Norisoprenoids and terpenes may be formed by acid-catalyzed molecular rearrangements of the released aglycones that take place to form more thermodynamically stable compounds. This is particularly relevant in the formation of norisoprenoids, which are known to derive from multiple precursors, including glycosides, carotenoids, and other volatile compounds. Examples include: 1-(2,3,6- timethylphenyl)but-3-en-2-one; 4-(2,3,6-trimethylphenyl)- butan-2-one with floral and fruity nuances; 1-(2,3,6- trimethylphenyl)buta-1,3-diene (TPB) wtih geranium leaf aromas; 1,1,6-trimethyl-1,2- dihydronaphtalene (TDN) with kerosene-like aromas; and vitispirane with, green and spicy descriptors [19]. 
  • Distillation with yeast lees (4% vol of lees vs none) was generally found to increase terpene concentrations, with Thibaud et al. (2020) hypothesizing that yeast lees may adsorb terpenes, and the heat of the distillation stops adsorption and helps to release it [15]. However, Thibaud et al. (2020) also found that linalool decreased and geraniol was not detected [15].
• Aging [15]
  Terpenes linked to the wine distillate’s age directly impact its aroma at 40% ABV:
  • 1,8-cineole is believed to be formed by the rearrangement of α-terpineol during aging.
  • Geraniol concentration tends to increase with distillate age. While at first appearing to be a contradiction, as geraniol diastereoisomer of nerol should follow the same tendency during aging, Ohta et al. (1991) during shochu distillation demonstrated that the catalytic rate constant for the transformation from nerol to α-terpineol was 11.1 times higher than that from geraniol to α-terpineol [15].
  • α-Terpineol concentration tends to increase with wine distillate age because nerol and linalool tend to rearrange under acidic conditions.  Therefore:
    • Nerol concentration may decrease.
    • Linalool concentration may decrease.
  • Linalool can easily be oxidized in linalool oxides.
  • Santalol, while a marker for aging in wine and derived from the precursors pyruvic and glutamic acids or a-ketobutyric acid, is not present in distillates [12].
  • Sotolon nor its precursors like pyruvic and glutamic acids or a-ketobutyric acid were looked for but not found in cognac distillates [12].

• Influence of ketones on terpenes
  • β-Damascenone and (Z)-whisky lactone enhance the perception of the mix of terpenes. 

Lactones 

• Maturation: Lactones in Cognac are derived from the extraction of wood compounds during oak maturation [1].
• Examples of Lactones found in Ledauphin et al. (2010): whiskey lactone (not detected in some samples) 

Volatile Phenol Formation and Concentration Influences

• Maturation: Volatile phenols in Cognac are derived from the extraction of wood compounds during oak maturation [1].
• Examples of volatile phenols in Cognac from Ledauphin et al. (2010): 4-ethylguaiacol, vanillin, and eugenol (not detected in some samples).

Fruran Formation and Concentration Influences [16]
Frurans are usually the product of a thermal reaction as they do not occur in nature. 

• In brandy, furans mainly originate from distillation and oak barrel aging.  

• Heat map clustering analysis confirmed higher furan compound concentrations in XO cognac than in VSOP. Yuan et al. (2023) suggested this is due to oak barrel aging, as longer aging increases the extraction of wood compounds, enhancing sensory characteristics. 
• Chemical reactions like oxidation, hydrolysis, esterification, and rearrangement also cause fruran concentration and composition changes throughout the aging process [11].
• Oak type and origin influence furan concentration as Limousin-oak barrel-aged Hennessy and Remy Martin cluster together, whereas Transeille-oak barrel-aged Martell forms its own cluster.
• Examples of furans in cognac include
  • 5-hydroxymethylfurfural
    • Aroma: Light, toasty, creamy-fudge flavors [17]  
    • In oak barrels, it is primarily derived from the degradation of hemicellulose during toasting. Its concentration is maximized at light-toasting levels [17]
    • The highest mean concentration found by Yuan et al. (2023) was 23.75–89.45 mg/ L [16]
  • 5-methylfurfural
    • Aroma: Medium Toasty, sweet caramel flavors [17]
    • In oak barrels, it is primarily derived from hemicellulose degradation during toasting. Its concentration is maximized at medium toasting levels [18]
  • Furfural 
    • Aroma: Dark toasty [17]
    • In oak barrels, it is primarily derived from hemicellulose degradation during toasting. Its concentration increases at higher levels of toasting [17]
    • Identified in previous studies as a characteristic biomarker associated with brandy aging [16] 
    • Average content found by Yuan et al. (2023):  >1 mg/L [16]
  • 2-methyl-5-formylfuran
    • Average content found by Yuan et al. (2023): >1 mg/L [16]
    • OAV range in iunaged cognac [9]: 2.62-4.5
  • ethyl 5-oxotetrahydro-2-furancarboxylate
    • Average content found by Yuan et al. (2023): >1 mg/L [16]
    • OAV range in unaged cognac [9]: 1.64-121.83

Your browser does not support viewing this document. Click here to download the document.

Differences between French Labeled Brandies

Ledauphin et al. (2010) found:

• Calvados can be identified by many possible acrolein derivatives and high amounts of butan-2-ol. 
• Cognac vs. Armagnac: Key differences stem from distillation methods. Cognac contains unique furanic compounds, while Armagnac features 1-(ethoxyethoxy)-2-methylbutane and γ-eudesmol. Both brandies have high isobutanol and isopentanol levels, unlike Mirabelle and Calvados, which are richer in aliphatic linear alcohols.

Sources and Suggested Reading

1. Lurton, L., Ferrari, G., & Snakkers, G. (2012). Cognac: production and aromatic characteristics. In Alcoholic Beverages (pp. 242-266). Woodhead Publishing. From www.researchgate.net/publication/286616777_Cognac_Production_and_aromatic_characteristics
2. Bureau National Interprofessionnel du Cognac (BNIC). (n.d.). Les cépages du Cognac. Retrieved from https://www.cognac.fr/decouvrir/vignoble/les-cepages/
3. Guittin, C., Maçna, F., Sanchez, I., Barreau, A., Poitou, X., Sablayrolles, J.-M., Mouret, J.-R., & Farines, V. (2022). The Impact of Must Nutrients and Yeast Strain on the Aromatic Quality of Wines for Cognac Distillation. Fermentation, 8(2), 51. https://doi.org/10.3390/fermentation8020051
4. Malfondet, N., Gourrat, K., Brunerie, P., & Le Quéré, J. L. (2016). Aroma characterization of freshly-distilled French brandies; their specificity and variability within a limited geographic area. Flavour and Fragrance Journal, 31(5), 361-376. From www.researchgate.net/publication/301907072_Aroma_characterization_of_freshly-distilled_French_brandies_their_specificity_and_variability_within_a_limited_geographic_area_Aroma_characterization_of_freshly-distilled_French_brandies
5. Bureau National Interprofessionnel du Cognac (BNIC). (n.d.). Les crus de l’appellation Cognac. From https://www.cognac.fr/decouvrir/vignoble/les-crus/
6. Watts, V. A., Butzke, C. E., & Boulton, R. B. (2003). Study of aged cognac using solid-phase microextraction and partial least-squares regression. Journal of agricultural and food chemistry, 51(26), 7738–7742. https://doi.org/10.1021/jf0302254
7. Thibaud, F., Peterson, A., Urruty, L., Mathurin, J. C., Darriet, P., & Pons, A. (2021). Sensorial impact and distribution of 3-methyl-2, 4-nonanedione in cognacs and spirits. Journal of Agricultural and Food Chemistry, 69(15), 4509-4517. https://doi.org/10.1021/acs.jafc.1c00643
8. Zanghelini, G., Giampaoli, P., Athès, V., Vitu, S., Wilhelm, V., & Esteban-Decloux, M. (2024). Charentaise distillation of cognac. Part I: Behavior of aroma compounds. Food Research International, 178, 113977. https://hal.science/hal-04394944v1
9. Ledauphin, J., Le Milbeau, C., Barillier, D., & Hennequin, D. (2010). Differences in the volatile compositions of French labeled brandies (Armagnac, Calvados, Cognac, and Mirabelle) using GC-MS and PLS-DA. Journal of agricultural and food chemistry, 58(13), 7782-7793. https://doi.org/10.1021/jf9045667
10. Yuan, X., Zhou, J., Zhang, B., Shen, C., Yu, L., Gong, C., Xu, Y. and Tang, K., 2023. Identification, quantitation, and organoleptic contributions of furan compounds in brandy. Food Chemistry, 412, p.135543. https://doi.org/10.1016/j.foodchem.2023.135543
11. Watts, V. A. (2003). Headspace analysis of aged cognac and California pot -still brandy. ProQuest Dissertations & Theses. https://www.proquest.com/docview/305344264
12. Cadahía, E., Fernández de Simón, B., & Jalocha, J. (2003). Volatile compounds in Spanish, French, and American oak woods after natural seasoning and toasting. Journal of agricultural and food chemistry, 51(20), 5923-5932. https://doi.org/10.1021/jf0302456
13. Thibaud, F., Shinkaruk, S., & Darriet, P. (2019). Quantitation, organoleptic contribution, and potential origin of diethyl acetals formed from various aldehydes in Cognac. Journal of agricultural and food chemistry, 67(9), 2617-2625. https://doi.org/10.1021/acs.jafc.9b01084
14. Thibaud, F., Courregelongue, M., & Darriet, P. (2020). Contribution of Volatile Odorous Terpenoid Compounds to Aged Cognac Spirits Aroma in a Context of Multicomponent Odor Mixtures. Journal of Agricultural and Food Chemistry, 68(47), 13310–13318. https://doi.org/10.1021/acs.jafc.9b06656
15. Ohta, T., Morimitsu, Y., Sameshima, Y., Samuta, T., & Ohba, T. (1991). Transformation from geraniol, nerol and their glucosides into linalool and α-terpineol during shochu distillation. Journal of fermentation and bioengineering, 72(5), 347-351. https://doi.org/10.1016/0922-338X(91)90085-U
16. World Cooperage. (n.d.). Toasting Cheistry.  From worldcooperage.com/toasting-chemistry/
17. Uselmann, V., & Schieberle, P. (2015). Decoding the combinatorial aroma code of a commercial cognac by application of the sensomics concept and first insights into differences from a German brandy. Journal of Agricultural and Food Chemistry, 63(7), 1948-1956. https://doi.org/10.1021/jf506307x