[The Bottle Exchange]

Charring is a process that many barrels of your favourite spirit go through.
Whiskey barrel science is concerned with a small group of compounds. There’s the cellulose, which creates a tight bond (but doesn’t really react with the whiskey itself), hemicellulose, lignin, tannins, and oak lactones. The extent to which you char a barrel will have an impact on those last four.

The hemicellulose is one of the most important components of American oak. When exposed to high levels of heat (284°F and above), hemicellulose will break down into wood sugars, allowing for some caramelization on the interior surface of the barrel. If you’ve ever enjoyed a bourbon with notes of brown sugar, caramel, or toffee, you’ve got hemicellulose to thank. Just don’t do it out loud. That’d be weird. Lignin is also very important, since that’s where vanillin (aka vanilla flavor) and spice come from. The more a barrel is charred, the more the lignin yields flavors of spice and smoke.

Tannins; well before the oak barrel is charred, the oak itself is “seasoned,” (allowed to dry out, often in the elements) to get rid of the harsher tannins. Those left over are essential for successful long-term maturation. The higher the char, the mellower the interaction between spirit and tannin.

The oak lactones; are compounds present in many species of oak tree, but in higher volume in American oak. Responsible for the woody/coconut flavors you’ll find in many bourbons. The higher the char, the less the impact of the oak lactones.

How much should a barrrel be charred? If a distiller wants to, they can char (or have their barrel producer char) as long as they please. Most don’t wanna over-char, of course, since that would basically be turning the oak compounds into carbon. Levels of char can vary depending on the barrel producer or distillery, but the most commonly used levels are #1 – #4.

Most barrels aren’t charred for more than 1 minute.
A No.1 Char is 15 seconds, No.2 is 30, No.3 (more common) is 35 seconds, and the classic No.4 Char is 55 seconds. The No.4 Char is also known as the “alligator char,” since after that duration of charring, the interior of the oak wood staves has the rough, shiny texture of alligator skin.

[Author]

Posts