Rum Aging Science - Part XI

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                                    Series Overview

The January 2020 issue of “Got Rum?” covers in detail the goals of this series, as well as, descriptions of the different equipment being used to collect and measure the data.

                                   October’s Weather

September brought much needed rain to our area in Central Texas, but October was drier than expected.  Instead of rain, October brought us unusually cold weather, with overnight temperatures near the freezing mark.  Lucky for us, mid-day and afternoon temperatures are still quite warm, so the aging cellar warms up during the day and the nights are not as unbearable inside the warehouse as outside.

Up until the last week of October, the average high temperature was 78F and the average low was 74F.  We then experienced a quick drop at the end of the month.

The humidity inside the cellar hit a minimum of 29% and a maximum of 80%, with an average of 52% for the month.  

                                          The Rum

After 10 months in the barrel, the rum is definitely starting to show signs of aging and maturity, not just tannic extraction.  The tannins extracted during the early months have been oxidized, but there are additional tannins still being extracted, such that the “oak” dimension of the rum is comprised of both oxidized and un-oxidized tannins.  The color continues to darken and the aroma is developing intensity and complexity.

pH: The rum that went into the barrel had a pH of 7.04.  This number is now 4.64, a slight numerical decrease from the previous month but a considerable increase in titratable acidity (keep in mind that the pH scale is NOT linear!).

ABV: The alcohol concentration increased a bit in the previous two months and did so again in October.  The current reading is 63.81%, meaning that, for another month, water evaporation was higher than alcohol evaporation from the barrel.

Coming up: November’s temperature should be similar to what we experienced in March, will this mean that the rum in the barrel will behave the same way too?

Join us again next month, to continue our exploration of this fascinating topic!