Rum Aging Science American Oak Barrels
Rum Aging Science - Rum Central
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. The future series will explore different Char and toast level combinations, as well as, barrels constructed using French Oak.
Understanding the US regulations for Whisky and Bourbon
The Code of Federal Regulations (CFR) defines, among many other things, “Standard of Identity” for distilled spirits produced in the USA. Here is an excerpt that applies to whisky in general:
27 CFR § 5.22 - The standards of identity.
National Archives and Records Administration
(a) Class 1; neutral spirits or alcohol. “Neutral spirits” or “alcohol” are distilled spirits produced from any material at or above 190° proof, and, if bottled, bottled at not less than 80° proof.
(b) Class 2; whisky. “Whisky” is an alcoholic distillate from a fermented mash of grain produced at less than 190° proof in such manner that the distillate possesses the taste, aroma, and characteristics generally attributed to whisky, stored in oak containers (except that corn whisky need not be so stored), and bottled at not less than 80° proof, and also includes mixtures of such distillates for which no specific standards of identity are prescribed.
(1)
Rum Aging Science Oak barrels
(i) “Bourbon whisky”, “rye whisky”, “wheat whisky”, “malt whisky”, or “rye malt whisky” is whisky produced at not exceeding 160° proof from a fermented mash of not less than 51 percent corn, rye, wheat, malted barley, or malted rye grain, respectively, and stored at not more than 125° proof in charred new oak containers; and also includes mixtures of such whiskies of the same type.
(ii) “Corn whisky” is whisky produced at not exceeding 160° proof from a fermented mash of not less than 80 percent corn grain, and if stored in oak containers stored at not more than 125° proof in used or uncharred new oak containers and not subjected in any manner to treatment with charred wood; and also includes mixtures of such whisky.
(iii) Whiskies conforming to the standards prescribed in paragraphs (b)(1)(i) and (ii) of this section, which has been stored in the type of oak containers prescribed, for a period of 2 years or more may optionally be further designated as “straight”; for example, “straight bourbon whisky”, “straight corn whisky”, and whisky conforming to the standards prescribed in paragraph (b)(1)(i) of this section, except that it was produced from a fermented mash of less than 51 percent of any one type of grain, and stored for a period of 2 years or more in charred new oak containers may optionally be designated merely as “straight whisky”. No other whiskies may be designated “straight”. “Straight whisky” includes mixtures of straight whiskies of the same type produced in the same State.
When it comes to whisky production, the bold and underlined words in item (i) are essential to the standard of identity: bourbon whisky MUST be aged in new oak containers.
Let’s take a look now at the standard of identity defined by the CFR for rum:
(f) Class 6; rum. “Rum” is an alcoholic distillate from the fermented juice of sugar cane, sugar cane syrup, sugar cane molasses, or other sugar cane by-products, produced at less than 190° proof in such manner that the distillate possesses the taste, aroma, and characteristics generally attributed to rum and bottled at not less than 80° proof; and also includes mixtures solely of such distillates.
As you can see, not only is rum not required to be aged, but those producers choosing to age their rums have no restrictions as to the type of oak containers (barrels) they can use.
This situation, where whisky producers are unable to re-use their empty barrels and rum producers are not required to use new barrels results in a perfect commercial relationship that explains why most of the aged rum around the world is aged in ex-bourbon barrels, which are cheaper and more readily-available than new barrels. Some rum producers opt, at a higher cost to their operation, to age in new oak barrels, and this impact on the rum is part of what we are exploring in this series.
These are the pH readings, as recorded on the 1st day of each month:
pH New Barrel Char #1 Ex-Bourbon Barrel
January 7.04 7.04
February 5.01 5.67
Rum Aging Science January weather, color and taste
Color: The color difference between new and used barrels is very significant too (refer above).
Taste: When comparing the 1-year-old sample and the 1-month-old sample, the rum from the new barrel definitely has a more intense oak aroma and taste, but this taste is mainly comprised of astringent, un-oxidized tannins that are not very pleasant.
Join us again next month, as we continue to explore the fascinating world of rum aging!