Rum Aging Science - American Oak: New vs. Used Part XI

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                                    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.

                                  October’s Weather

October’s daily temperatures were a bit warmer than expected during most of the month.  The average temperatures only started to drop significantly during the last week, bringing much-needed fresh air to the area.  The daily deltas (the differences between the highest and lowest temperatures each day) continue to be significant, resulting in high rates of extraction from the barrels.

We expected more rain in October than what we actually received.  In fact, there were a couple of periods of extremely-dry air, as shown on the graph, where the relative humidity inside the warehouse fell below 30%.

We are quickly approaching the end of the series, and the rum keeps getting darker, richer and more complex.  This rum was darker and had more wood-extractives after one month in a new barrel than the rum we aged in an ex-bourbon barrel for a whole year, but more about this next month, when we wrap up this series.

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.  Notice the reduction in pH (increase in alkalinity):

And these are the changes in ABV % readings (as of first day of each month), also compared to the ex-Bourbon barrel:

Color: The monthly change in color continues to be measurable through colorimetry and is definitely noticeable to the naked eye.

Aroma: The wet oak, almond and coconut/nutty notes characteristic of American Oak are in full display.  The aroma is enticing and very promising.

Taste: The organoleptic transformation continues, with all notes gaining in intensity after each passing month. The oxidized tannins are becoming more noticeable, but fresh (un-oxidized tannins) are still present due to their continuous extraction from the staves. 

Join us again next month, as we continue to explore the fascinating world of rum aging!