2019 How Oxygen Enters and Interacts with Distillate in Whiskey Barrels Aged in Various Locations in Aging Warehouses

Funded $7000
Name: Conor O’Driscoll


Distillery Manager/Master Distiller, Heaven Hill Distillery


Bachelor of Chemical Engineering, University College Dublin, Ireland

Distilling Experience:

2004 – 2009, Brown-Forman Distillery, Louisville. 2009 – 2017, Woodford Reserve Distillery, Versailles. 2017 – 2019, Angel’s Envy Distillery, Louisville. 2019-present, Heaven Hill Distillery, Louisville.

Research Experience:

Co-investigator is Dr. Seth DeBolt, University Alumni Professor, University of KY. His resume is attached.

Please provide how your background experience will provide the foundation for your research:

In prior work, we have established the dissolved oxygen rates in wine barrels (Study in real-life conditions of liquid and oxygen transfers through a barrel when aging a wine in a cellar ZAC de la Garosse –250 rue des droits de l’Homme, 33 240 Saint-André-de-Cubzac NewsletterRetD@chene.fr-+33(0)7 89 63 65 54)(PDF attached). These data revealed that the negative pressure induced by barrel aging conditions results in abrupt changes in barrel oxygen levels over time in a wine setting. This is expected to be exasperated in a whiskey barrel, but to date no evidence has been produced on this subject. This research will provide foundational information on this subject. Given that whiskey barrels undergo dramatically different temperature conditions over the diurnal and seasonal range, we anticipate that understand dissolved oxygen in barrels will in turn allow for American whiskey producers to make detailed determinations on maturation cycles and predict how this may create oxygen driven reactions for flavor creation. Collectively, the output of these data could provide a rationale for reduced energy inputs, such as steam cycling, which in turn could reduce energy footprints and improve sustainability. Dr. DeBolt (co-investigator) has published over 80 peer-reviewed research articles on a variety of subjects including carbohydrate saccharification, wine, and whiskey barrels. The monitoring methods in this study are consistent with the experience he brings to the project in design and delivery of research. Furthermore, Master Distiller for Heaven Hill Conor O’Driscoll (Chemical Engineer) brings a wealth of experience in distilling and maturation facility operations and process chemistry. The teams at Canton Cooperage and Independent Stave Companies provide sophisticated support for all monitoring and barrel construction. Their cooperation in barrel comparisons will provide additional research outputs that are relevant to both craft and heritage distilleries. Further, Dr. DeBolt has published several papers on environmental monitoring, chemical analyses, and sensory profiling (see CV in appendix) and has gas chromatography-mass spectrometry (GC MS) and liquid chromatography tools dedicated to whiskey research. Methods relevant to this research involve environmental data logging, as well as mapping and modeling of data (DeBolt et al., 2008; Gollihue et al., 2018).


The project will define how oxygen enters and interacts with distillate in whiskey barrels aged in various locations in aging warehouses at Heaven Hill distillery, Bardstown KY, with toasted versus charred white oak barrels as primary treatments. Outcomes of the dissolved oxygen study will provide critical clues to inform cultural treatments and aging paradigms for achieving quality barrel-aged products.

Proposal Background:

Oxidation occurring in food products is generally thought to be negative and attributed to spoilage, in whiskey however this reaction is critical to flavor development. Though Fenton chemistry is still yet to be understood completely, the signs of this chemical process have been documented as ethanol changes to acetic acid and acetaldehyde1,2,3. Fenton chemistry in wine has been documented and while the mechanisms of this process are still being divulged4-5. the generation of hydrogen peroxide has been documented. The hydrogen peroxide is produced from phenolic compounds reacting with oxygen and the charge state is regenerated from iron and copper ions6-7. The implications of these reactions in whiskey maturation are extremely interesting and should be explored as many volatiles will be produced as has been previously observed in port8, cheese or cooking oil9-10. There are some factors that should be considered in influencing oxidation rates in whiskey that the process is going to be influenced by composition polyphenolic, transition metals content, pH, temperature and dissolved oxygen content5. Barrel wood after pyrolysis is biochar and would have the ability to adsorb and desorb various compounds and metals, this would be an interesting area of study to understand these relations particularly during secondary use of the barrel 11-1251,82. Thus, we propose to examine both charred and toasted barrels as independent variables.


Several in situ methods are embedded into the CHENOX device (patent pending). These devices deliver O2 and CO2 determinations, but we also embed pressure sensors for gaseous atmosphere, density measurement and spatial differences in pressure between the top and bottom of the barrel (assuming no rotation). These methods are standard and reported in Canton (2019) in the attached PDF. The data logging and reporting between different levels in the rickhouse is aided by the use of Heaven Hill maturation facilities. Here, we will compare the lower, middle, and upper floors of the rickhouse to determine statistical variation in pressure compared between floors. Statistical tests will be aided by the University of Kentucky James B Beam Institute for Kentucky Spirits. In-house statistician assistance is available to compare treatments across floors and between replicates.


Please see attached project brief for full details.


This research will provide critical data for any scale of distiller wishing to barrel age a spirit. It will provide knowledge on where to maximize oxygen driven reaction chemistry based on the position of the maturation facility and relate this information to logged temperature and humidity data. We will present this freely to the ADI community to allow craft distillers to how to mature their barrel-aged spirit. Depending on findings, we feel these data are going to be important for sustainability and deciding whether to age using steam cycling. It will point to the optimal point for oxygen intake rates, which are critically important to flavor development.


In addition to the references listed in the attached proposal, the following work is also relevant:

DeBolt S, Ristic R, Iland PG, Ford CM (2008) Altered light interception reduces grape berry weight and modulates organic acid biosynthesis during development. HortScience 43: 957-961.

Canton Cooperage (2019) Study in real-life conditions of liquid and oxygen transfers through a barrel when aging wine in a cellar ZAC de la Garosse –250 rue des droits de l’Homme, 33 240 Saint-André-de-Cubzac NewsletterRetD@chene.fr-+33(0)7 89 63 65 54

Gollihue, J, Mitchell Richmond, Meera Nair, Harlan Wheatley and Seth DeBolt (2018) Liberation of recalcitrant cell wall sugars from oak barrels into bourbon whiskey during aging Scientific Reports 15899.