Rum Aging Science2
Introduction to Rum Aging Science
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 gather the data.
February’s Weather
The month of February was almost as cold as January. The humidity inside the cellar ranged from 35% to 89%, with very large variations occurring even from one day to the next.
Humidity
The temperature inside the cellar ranged from 39F to 60F, the dew point and heat index not too far away, as depicted below.
Temperature
The Rum
The change after 2 months in the barrel was not as drastic as it was after the first month.
Color: The color is almost identical to the naked eye as it was 30 days earlier. The spectrophotometer indicates it is a few shades darker, but nothing to write home about.
Aroma: The aroma is still predominantly that of the control (unaged) sample, only hints of oak are present in the background. The oak notes are very ‘wet’ and somewhat ‘green,’ despite the charred inner surface of the barrels.
pH: The rum that went into the barrel had a pH of 7.04. This number was 5.67 after the first month of aging and it is now 5.32. Before jumping to conclusions about why this change is not linear, read the section below about the pH scale.
ABV: The ABV remained the same as the previous month: 63.42%.
Samples in each barrel
pH Scale Explained
The abbreviation pH stands for “potential of hydrogen ion.” The term was coined by the Danish biochemist Søren Sørenson, who defined the “p” as instructions to take the negative of the logarithm of the hydrogen ion concentration, written [H+]. pH is the negative logarithm of the molarity of H, which is a measure of total ions per unit volume rather than mass per unit volume. For each 1-unit change in pH, the hydrogen ion concentration changes ten-fold. In other words, the amount of acid required to change the pH of water from pH 7 to pH 6 is one tenth of the amount required to take it from pH 6 to pH 5. Why is this important? Because each day the rum is inside the barrel, the amount of ethanoic (acetic) acid increases, which then leads to formation of esters, particularly of ethyl acetate.
Join us again next month, to continue our exploration of this fascinating topic!