Rum Aging Science American Oak Barrels
Rum Aging Science Oak barrels
Introduction
In our first 12-part series, published from January through December 2020, we explored the transformation of rum, while aging in an ex-whiskey barrel. We selected an ex-whiskey barrel for that initial series because the majority of the rum aged around the world employs this type of barrel. The reason for the popularity of this choice is the fact that whiskey producers are required to age their spirit in new oak barrels and, once emptied, they cannot re-fill the barrels, thus creating a surplus of barrels that many other spirits are happy to use in their aging programs.
During the course of the first series, we received a considerable number of inquiries, asking how the results presented would differ if we were using new barrels. This new 12-part series is devoted specifically to address this topic: we will be conducting the same type of research as we did previously, examining the month-to-month changes to the rum while it ages in a new barrel, but also presenting side-by-side comparisons to the corresponding results from the used barrels.There are many different levels of heat treatment that can be applied to a new barrel. This series focuses exclusively on American Oak with a Char #1 (staves and heads), from Independent Stave Company/Missouri Cooperage. Future series will explore different Char and toast level combinations, as well as, barrels constructed using French Oak.
May’s Weather
The first 10 days of May suggested that summer was right around the corner. The remaining 20 days of the month, however, had cooler plans in mind. Daily rains and cooler mornings surprised everyone, even delaying the emergence of the Brood X (17-year) cicadas, which were expected to invade parks and backyards as early as May but which, as of this writing, have remained hidden.
Temperature for May
Frequent (almost daily) rains have resulted in steadily-high levels of humidity, both inside and outside the aging cellar.
Humidity for May
Heat’s Magic
The higher temperatures are accompanied by higher extraction rates from the barrels. Not only does solubility increase, but the volume of the rum also increases inside the barrel, causing higher pressure which, in turn, forces the rum deeper into the staves.
The increased volume also results in higher evaporation losses and leakage. The chart below shows that despite the unusually cool weather in May, Year-To-Date temperatures have been steadily rising.
Year to date temperature
The Year-To-Date humidity readings paint a very good picture of increased and consistent humidity in May, more so than during any other month of the year.
Year to date Humidity
Color transformation of rum for May
These are the pH readings, as recorded on the 1st day of each month, compared to the rum from the previous series, which was aged in an ex-Bourbon barrel:
Reading for Ex Bourbon Barrel in May
And these are the changes in ABV % readings, also compared to the ex-Bourbon barrel:
ABV Ex Bourbon barrel
Color: The monthly change in color continues to be significant, even to the naked eye. The last sample retrieved from the barrel has deeper reddish-copper hues that make it more appealing.
Taste: The rum’s flavor has a more pronounced oak dimension, as suggested by the color. The majority of the extracted tannins are still “harsh,” meaning un-oxidized, but are nonetheless helping to make the rum more interesting and complex. The reduced pH (increased acidity) is also starting to come across, with enhanced fruity notes starting to develop.
Join us again next month, as we continue to explore the fascinating world of rum aging!