Rum Aging Science Vol. 3: American Oak vs. French Oak, Part 12

by ,

Introduction

In Volume 1 of Rum Aging Science (published from January through December of 2020), we explored the aging of rum in American Oak, ex-Whiskey barrels.  In Volume 2 (published from January through December of 2021) we explored the aging of rum in new American Oak barrels.  This year’s Volume explores the aging of rum in French Oak barrels.

The Rum: Just as we did in Volumes 1 and 2, this new series starts using a low-congener, column-distilled rum, made from fermented HT (High Test or “miel virgen”) molasses.  We use low-congener rum so that we can focus more on detecting the wood extractables and their impact on the rum’s profile.

The Barrel: For this series we selected a barrel made by Independent Stave Company (https://www.independentstavecompany.com), with toasted staves and Char #1 heads.

The Wood Extractives: The compositions of both American Oak and French Oak have a lot of things in common: they are, after all, both oaks.  But the proportions of the components that are extractable by alcohol differ between the two types of oak.  These extractives include:

  • Cellulose - is the most abundant natural polymer on earth.  It consists of linear chains of glucose units and remains relatively intact even after wood curing and toasting.
  • Hemicellulose - also known as a “wood sugar” is a two-dimensional polymer comprised of many simple sugars, including: Glucose, Xylose, Mannose, Arabinose, Galactose and Rhamnose.
  • Lignin - despite the fact that it is also one of the most abundant nature-produced materials on earth, lignin remains one of the least understood.  Oak ligning consists of two building blocks: guaiacyl and syringyl.  The former is responsible for producing coniferaldehyde, vanillin and vanillic acid, which -especially the vanillin- are easily recognized in cask-condition spirits.
  • Oak tannins - these plant polyphenols derive their name from the Latin word tannum, which means “crushed oak bark,” since in early times oak trees served as a major source of tannin for the leather-tannin industry.  Tannins improve aged rum’s character by increasing the perception of balance, complexity and roundness.

Scope of Study

Each month we will evaluate a sample of the rum collected from the barrel and will report its pH, ABV and color. We’ll compare these results agains those obtained from the rums in volumes 1 and 2.

Rum aged in a new, French oak barrel, after 12 months

Our rum has now spent a year inside its barrel at Rum Central’s aging cellar.  The temperature during the month of November was very cold and mostly humid.  The overnight temperature dipped below the freezing point several nights.

Organoleptic Changes

It is amazing how one year can transform a white rum into a multi-faceted, complex, more enjoyable version of itself.  Although not all tannins are oxidized (there is still active tannic extraction from the barrel), the oak dimension is smooth and inviting, with leather and soft spicy notes of cinnamon and nutmeg, enveloped by fruity notes from the acidity and esters from the rum.

                                        Physical Changes

These are the pH readings, as recorded on the 1st day of each month, compared to the rums from the previous Volumes, which were aged in American Oak barrels:  

And these are the changes in ABV % readings (as of first day of each month), also compared to the American Oak barrels:

We’ve reached the end of Volume 3 of Rum Aging Science, stay tuned for additional material on other fascinating topics.